2013 Fall Medium Range Discussion

[Ottawa Blizzard]

At 11 pm, tempertures included 20° in Washington, DC, 16° in Philadelphia, 14° in New York City, and 15° in Boston. Winter's coldest period, likely to stretch 3-4 weeks from this point into the middle or perhaps latter part of February has probably gotten underway.

 

Based on ENSO (neutral to borderline La Niña conditions for February and the teleconnections into early February/weight given to some of the past years for teleconnections similar to those of this winter), the most persistent teleconnection analog for February is 1967. The second one is 1963. A distant third was 1962. Those analogs suggest that the eastern half of the U.S. and southern Canada could be colder than normal for February.

 

My latest teleconnection analogs for February 2013 result in the following temperature anomalies:

 

All three of those years saw some frigid readings in that area during the first half of February. 1963 saw the cold last through much of the month. Needless to say, the baseline temperature normals (1981-2010 vs. 1951-80) have warmed. Nonetheless, even taking that into consideration it is likely that the coldest reading could be near 0° in Boston (a subzero low cannot be ruled out), between 7° and 12° in New York City and Philadelphia, and probably between 12°-17° in Washington, DC by the worst of the cold ends by mid-February.

 

Nationwide, February 1967 was the 48th coldest February on record. However, in the Northeast it ranked 17th, Ohio Valley 27th, and Southeast 25th. While I don't believe readings will approach the levels of 1967 given the contemporary baseline norms, the important point is that the Ohio Valley, Northeast (New England/Mid-Atlantic), and Southeast could be colder and perhaps much colder than today's norms.

 

In terms of snowfall, February will probably prove to be the snowiest month of the winter. Snowfall in the Middle Atlantic and New England regions and possibly Ohio Valley could be above normal.

 

1967 featured a KU snowstorm during the February 5-8 timeframe. During the onset of the snowstorm, the GWO was in Phase 4, the AO was neutral and the PNA was positive (a PNA and AO scenario that is plausible going into the first week in February according to the GFS ensembles). In terms of February KU snowstorms, Phase 4 was actually an uncommon one. Phase 8 was the most common (37%). Phases 6-8 accounted for 63% of February KU snowstorms. Phases 1-5 accounted for just 37% of KU snowstorms. Recently, the GWO was in Phase 5.

 

On account of the KU snowstorm, the Mid-Atlantic and New England areas were much snowier than normal in 1967. In contrast, 1963 saw much less snowfall, but that year featured an exceptionally cold February (among the 10 coldest in the Northeast and Southeast). 1962 saw above normal snowfall in the Mid-Atlantic region and much above normal snowfall in New England.

Don, two of the greatest february cold fronts to hit Toronto and Ottawa in recent decades occurred in February 1967. One of them was on February 11,1967.

[uncle W]

Don, two of the greatest february cold fronts to hit Toronto and Ottawa in recent decades occurred in February 1967. One of them was on February 11,1967.

that front on the 11th in 1967 brought the coldest temperatures of that winter for NYC...1963 had its share of strong cold fronts...Here's a picture from this date in 1976 in Toronto...

http://world.nycsubway.org/perl/show?81867

[stemwinder]

Great discussion.  I'm old enough to remember Feb. 1967 in the NYC area, and March was quite a month as well.  Cold, snow, and a significant snow on the equinox, dry and powdery.  Something to consider if this year does follow that pattern.

[uncle W]

Great discussion.  I'm old enough to remember Feb. 1967 in the NYC area, and March was quite a month as well.  Cold, snow, and a significant snow on the equinox, dry and powdery.  Something to consider if this year does follow that pattern.

at age 13 in 1962 I was becoming a weather watcher...Around the equinox in 1962 there was a very light wet snowfall the evening of the 21st...There was a dusting in spots...The West End El on New Utrecht Ave in Brooklyn had a dusting on the wooded platform...In 1963 there was a surprise snowfall the evening of the 20th...Rain changed to snow that evening... that wasn't forecasted...An inch to half inch accumulated on exposed surfaces...1964 had a 5" wet snow event the first day of Spring...1965 had a 2" powdery snowfall around the 21st...1967 was under forecasted the night before...I remember playing stickball in the snow days later...1967 was the coldest spring of my lifetime...

[stemwinder]

I do remember the cold spring, because I was working outdoors on the Harbor, in a job I was totally unfit for.  The summer was a wet one, but not too hot, I remember.

 

You have a great memory for weather.  I remember just the parts that stood out for me.

[Srain]

As outlined in post 546, the next in a series of storm systems that includes a potential significant severe episode event is developing across the W. For those interested in following this event, an ongoing thread is located in the Central/Western sub forum…

 

http://www.americanwx.com/bb/index.php/topic/38901-end-of-january-active-weather-for-the-plains/

 

SHORT RANGE FORECAST DISCUSSION
NWS HYDROMETEOROLOGICAL PREDICTION CENTER COLLEGE PARK MD
312 AM EST SUN JAN 27 2013

VALID 12Z SUN JAN 27 2013 - 12Z TUE JAN 29 2013

...UNSETTLED WEATHER CONTINUES WEST OF THE ROCKIES....

...A CHANCE OF MIXED WINTRY PRECIPITATION FROM THE CENTRAL PLAINS
AND INTO THE MIDDLE ATLANTIC...


THE UPPER LEVEL LOW THAT WAS AFFECTING THE NORTHERN PACIFIC COAST
HAS PUSHED PASSED INLAND AND IS SLIDING OVER THE ROCKIES.  THE
PRECIPITATION BEING CAUSED BY THIS LOW IS NOW SPREADING INTO THE
NORTHERN ROCKIES AND THE NORTHERN HIGH PLAINS.  HOWEVER...SURFACE
TROUGHS WILL CONTINUE TO BE THE AXIS OF FOCUS FOR PRECIPITATION ON
THE NORTHERN PACIFIC COAST.  THIS ACTIVITY IS EXPECTED TO LAST
THROUGHOUT THE SHORT RANGE PERIOD.

THE DISTURBANCE THAT WAS CONTRIBUTING TO THE RAIN AND SNOW IN THE
DESERT SOUTHWEST IS EJECTING INTO THE CENTRAL PLAINS. AS THIS
OCCURS...THE PRECIPITATION SHIELD WILL CONTINUE TO DISSEMINATE
FROM THE CENTRAL PLAINS INTO THE GREAT LAKES ON SUNDAY.  A
BOUNDARY CURRENTLY DRAPED OVER THE SOUTHERN PLAINS WILL ALSO BE
MOVING NORTH AS A WARM FRONT.  THESE TWO FEATURES TOGETHER WILL
ENHANCE THE CHANCE OF WINTRY PRECIPITATION...IN THE FORM OF
FREEZING RAIN...TO OCCUR BEGINNING SUNDAY AFTERNOON.
CONSEQUENTLY...THERE ARE CURRENTLY WINTER STORM
WATCHES...WARNINGS...AND FREEZING RAIN ADVISORIES ACROSS THE UPPER
MID-WEST AND UPPER GREAT LAKES REGION.  AS THE FRONT EVOLVES AND
PUSHES EASTWARD...THE FREEZING RAIN WILL MOVE INTO THE OHIO VALLEY
ON SUNDAY NIGHT AND ARRIVE IN THE MIDDLE ATLANTIC BY MONDAY
MORNING.

AS THE FRONTS BEGIN TO CONSOLIDATE BY MONDAY...MOST OF THE
FREEZING RAIN WILL BE CONCENTRATED IN THE NORTHEAST.  FURTHER
SOUTH...SHOWERS AND THUNDERSTORMS WILL BEGIN TO DEVELOP IN THE
SOUTHERN PLAINS AND STRETCH INTO THE OHIO VALLEY.  FOR MORE
INFORMATION ON WHETHER THESE THUNDERSTORMS ARE EXPECTED TO BECOME
SEVERE...VISIT THE STORM PREDICTION CENTER'S WEBSITE AT
WWW.SPC.NOAA.GOV.


FANNING

 

[QVectorman]

Here is a quick POP over the last few weeks. Thanks guys!

I extended my outlook through Jan 8 on Dec. 14. I still feel comfortable with those dates and with the newest GWO analogs and latest 10 and 30 mb temp forecast it appears the time frame between 1)Jan 7-10 will see a warm up over the east with a 2)short wave moving through the east Jan 10-11 with cooler air dropping in behind it for 3)Jan 10-13 across the MW/GLKS and then pockets of cooler air arriving 4)Jan 15-19 time frame for the east followed by a 5)second reinforcement of cooler air Jan 20-24. My GWO analogs only take me out to Jan 9 so there may be another short wave or two to add to the 2 already expected for the Jan 9-24 time frame. I will update as the newest GWO numbers come out over the next week and half.

 
Correction to forecast Jan 5 on warm for Jan 11-13 time frame....
 
Posted by QVectorman on 5 January 2013 - 03:11 PM in New England
I had conflicting strat and GWO signals for the 10-13 time frame and I assumed that the strat signal for cold would over whelm the GWO signal for warmth and the cold air would dominate for that time frame. But the GFS seems to be hinting that the GWO will dominate instead for that time frame. 6)Which would change it to warm from Jan 8-10 then a fall in 850 temps for 1 or 2 days after peak in 850 temps then a spike in 850 temps Jan 11-13 which would put us back on track to a fall in 850 temps 1 or 2 days after that which lines up with the Jan 15-19 time cold pocket that I have forecasted previously. I still stand by a shortwave tracking through the central/eastern US although it may be weak Jan 10-11 as I stated last month.
 

It appears the Jan 20-24 cold shot should be comparable in magnitude of the upcoming Jan 2-3 airmass. Also latest GWO numbers are currently trending towards an agreement of the Jan 20-24 date. I will have concrete confirmation or rejection of that assumption by Tues.

Extending the outlook 7)Jan 24-26 show up as next pocket of cooler air...although I will say signals are mixed on this window date so I'm not too confident on this time frame producing a cooler airmass for the MW/NE.

Although 8)Jan 26-30 looks very impressive and should out do the Jan 2-3 850mb cold air wrt temps.

I will also say that it appears a lot of these dates are back to back and should mention that these forecasted chunks of cooler/colder air are cooler/colder relative to the air in place that they displace. So I don't claim to know the temperature range of the 850mb temps arriving...The concept can only forecast that it will be "colder" than the one that will be in place at the time of it's arrival and are associated with shortwaves so there will be brief time frames of southerly winds ahead of the short waves that will produce WAA ahead of waves and as a result might produce brief minor spikes in 850 temps and sfc temps in transition from time frame to time frame. When the signals are stronger an estimation of the temp of the air is possible such as the Jan. 2-3 and Jan 20-24 and Jan 26-30 episode. The other time frames are just hiccups in the stat. signal and coincide to minor dips in sfc temperatures relative to previous days' highs but I figure they are worth mentioning.

Forecast of -33C temps along Canadian border...although I was about 4 days off and I adjusted the Jan 26-30 date to Jan 27-29 back on Jan 6.

The GWO analogs eluded to this second warm up all the way back on Dec. 14. It will be short lived with the warmest air being tempered by cooler/colder air arriving in the Jan 15-19 range moving into the Jan 20-25 range with much colder air. Based on GWO and strat. analogs I'm guessing the coldest core of the 850 temps behind the short waves for the Jan 15-19 time frame will remain warmer than -15C then be reinforced with a coldest core of -15 to -25C for Jan 21-25 with a core of cold in the -25 to -30C range possibly as cold as -36C at some point for Jan 25-30. With -33C sneaking over the northern plains or GLKS or NE. Of course the cores of the coldest air will probably remain north of the border but still one can extrapolate what kind of 850 temps would be making down to the central US with those types of 850 temps just north of border.  With shortwaves arriving with more cold air for Jan 24-27 and Jan 27-29 and Feb 1-5. Though it appears the last week of Jan into Feb again would be the coldest air. Of course as stated before the caveat to these is how strong is the southerly flow ahead of these shortwaves that will also produce a spike in temps a day or two before the wave. So a strong wave will have a strong flow and could really spike temps for a day or two before it's arrive too. 

1)Jan 7-10 will see a warm up over the east
2)short wave moving through the east Jan 10-11
3)Cooler Jan 10-13 -----CORRECTED in 6)
4)Cold Jan 15-19 time frame  
5)second reinforcement of cooler air Jan 20-24
6)warm from Jan 8-10 then a fall in 850 temps for 1 or 2 days after peak in 850 temps then a spike in 850 temps Jan 11-13
7)Jan 24-26 pocket of cooler air  
8)Jan 26-30 cold or S/W-->Jan 27-29

I covered the S/W verification for event 2) for Jan 10-11 a couple weeks ago in my last POP post along with Event 1 so quick
run down of the rest of these...I was off by about 4 days on the coldest temps, they settled in Jan 22 not the 24/25 like I
expected. But we did see -33C at the MN/Can border on Jan 21. The Jan 27-29 cold shot didn't materialize the S/W is there but it didn't track far enough east to bring down any cold air so we have warmer temps east of the MS. Then on top of that we have another S/W right on it's heels that I spoke about back on Jan 18th which has strong southerly flow ahead of it that will spike temps for the 29 and 30th with just as strong cold blast behind it. This is one of those situations that I always had disclaimers about LOL.

DTW meteogram

850 temps for Jan 21

SW for Jan 27

[QVectorman]

Last half of Feb looks banging with plenty of S/W's. Recap....we had xt RTW that was in the pacific last wednesday arrived on the 24 early 25th in a couple pieces. The RWT that was over India last week is still expected to arrive Feb 4 or 5 it appears as a clipper. Behind this RWT we will see a shot of cold Feb 5-7. Then Feb 7 or 8 another RWT which was over Africa last week should arrive and colder air moving in behind it for Feb 7-11. This one started off at a pretty high latitude so I believe it will be a weak clipper. It appears after that we will see at LEAST at 5-10 degree warm up for Feb. 11-13 ahead of the next system that will pass through the east Feb 14 or 15 with a quick shot of cooler air behind it before another S/W arrives Feb 18 or 19th (tentative)The pattern is really chaotic as HM, others and myself have noted so it's harder to bit on the signals 4 weeks out right now so I am waiting for newer GWO data to reconfirm or disprove my thoughts about S/W's beyond Feb 14, part of the reason why I left the Feb 18/19 S/W tentative because the arrival date may change +/-1 day. But tentative dates I have for other S/W's and shots of cooler air are feb 21-25 and Feb 27-March 3.

In regards to over all temps rehashing last week's ideas the vortex is forecasted to re-consolidate by the 29th As a result, the main PV will restrengthen it's vortex walls and the gushing cold air faucet will be turned off. Just as there is a 1-3 week lag for it to arrive here there should be a 1-3 week lag of the last pockets of cold air to arrive down here in the US. Which would line up to carry us through with colder air to just about middle of Feb. So the last 2 weeks of Feb I think we will see normal to slightly above normal anomalies take over the East coast. As the AO starts its accent into more consistent positive territory after Jan 29....when the PV re-consolidates. Also matches up with the MJO dynamical forecasts that would take us into phase 2/3 by mid Feb resulting in a warmer or more seasonable scenario for the last half of Feb. I just have a feeling when using the strat. and GWO analogs that the base state of the 850 temps for Feb will be warmer so the cooler air won't be as cold over the region like we have for the end of Jan. Snowfall across the region looks about normal to slightly above normal. Big winners look like a line from KS to upper WI for Feb. I think as the general storm track shifts west with a -PNA for the second half of the month.

 

 

I don't see the demise of winter though. My 3 month temp analogs have March running near normal across the NE and below normal for the GLKS. So there is a gradient there. Along with a snow gradient...GLKS cashes in for Marchs while the NE can either be near normal or just horrendous snowfall totals. Seems to be dependent on the PDO. If the PDO can avg. above .5 for about 4-6 weeks during Feb or early March then the NE sees near normal snowfall if the PDO is below .5 or negative the NE gets screwed. And with a PDO>.5 the NE sees below normal temps also. IDK...just and interesting trend I noticed in my neutral ENSO years. Who knows if it's statistically significant.

 

[Mike.Ventrice]

Last half of Feb looks banging with plenty of S/W's. Recap....we had xt RTW that was in the pacific last wednesday arrived on the 24 early 25th in a couple pieces. The RWT that was over India last week is still expected to arrive Feb 4 or 5 it appears as a clipper. Behind this RWT we will see a shot of cold Feb 5-7. Then Feb 7 or 8 another RWT which was over Africa last week should arrive and colder air moving in behind it for Feb 7-11. This one started off at a pretty high latitude so I believe it will be a weak clipper. It appears after that we will see at LEAST at 5-10 degree warm up for Feb. 11-13 ahead of the next system that will pass through the east Feb 14 or 15 with a quick shot of cooler air behind it before another S/W arrives Feb 18 or 19th (tentative)The pattern is really chaotic as HM, others and myself have noted so it's harder to bit on the signals 4 weeks out right now so I am waiting for newer GWO data to reconfirm or disprove my thoughts about S/W's beyond Feb 14, part of the reason why I left the Feb 18/19 S/W tentative because the arrival date may change +/-1 day. But tentative dates I have for other S/W's and shots of cooler air are feb 21-25 and Feb 27-March 3.

In regards to over all temps rehashing last week's ideas the vortex is forecasted to re-consolidate by the 29th As a result, the main PV will restrengthen it's vortex walls and the gushing cold air faucet will be turned off. Just as there is a 1-3 week lag for it to arrive here there should be a 1-3 week lag of the last pockets of cold air to arrive down here in the US. Which would line up to carry us through with colder air to just about middle of Feb. So the last 2 weeks of Feb I think we will see normal to slightly above normal anomalies take over the East coast. As the AO starts its accent into more consistent positive territory after Jan 29....when the PV re-consolidates. Also matches up with the MJO dynamical forecasts that would take us into phase 2/3 by mid Feb resulting in a warmer or more seasonable scenario for the last half of Feb. 

 

I think that the MJO phases 4-6 are the typical US warm phases for DJF months... no?

[am19psu]

I think that the MJO phases 4-6 are the typical US warm phases for DJF months... no?

P1 is deceptively warm in Feb. P3 is the icebox. And, yes P4-P6 are full on torches.

[Mike.Ventrice]

P1 is deceptively warm in Feb. P3 is the icebox. And, yes P4-P6 are full on torches.

 

Ok good I made these time-lagged regressions of 1000 hPa temp anoms based off MJO-filtered VP200 anomalies over the Indian Ocean. They show torch when the MJO moves over West Pacific and into the East Pac. Was wondering if I had a coding error somewhere

[Roger Smith]

Here's my contribution to the mix:

 

Expect record high temperatures for most of a week to ten day period around mid-February to 25th or so. Reason is from research strong indications of a major height building episode over the Great Lakes and northeast U.S. at that time. Overall reason (since that's really just the same prediction in upper air terms) has to do with solar system magnetic field structure and earth's approach to J-1 field sector. Analogues include 1930 and 1954 which both set numerous record highs in February.

 

The pattern before that may be highly variable with brief shots of -10 anomaly arctic air interspersed with +3 type warm sectors in a generally WNW flow, in other words, clippers on parade. This would be a rather dry pattern for many with some lake effect squall opportunities. The warm spell will be massive for central-eastern regions and could involve rain/drizzle/fog into far northern plains states as well as northern New England, and an early snow melt in those regions and even into parts of nw to n/c ON and s MB except for possibility of major snowfall western MB into SK and MT.

[easternsnowman]

I think many agree on a late Feb warmup of some sorts. We're all hoping for some kind of winter storms after that into mid march or so, I'm not an expert but I suppose there is some hope there....after all we are due especially after the last 3 seasons where march produced hardly anything.

[QVectorman]

I think that the MJO phases 4-6 are the typical US warm phases for DJF months... no?

I was using this composite for DJF which shows some warmth for phase 3 when compared to phase 2 just not as dramatically warm as 4/5/6 http://www.cpc.ncep.noaa.gov/products/precip/CWlink/MJO/Composites/Temperature/

Thanks for the new composites Mike!! I'm not too fond of the NCEP ones.

[uncle W]

Here's my contribution to the mix:

 

Expect record high temperatures for most of a week to ten day period around mid-February to 25th or so. Reason is from research strong indications of a major height building episode over the Great Lakes and northeast U.S. at that time. Overall reason (since that's really just the same prediction in upper air terms) has to do with solar system magnetic field structure and earth's approach to J-1 field sector. Analogues include 1930 and 1954 which both set numerous record highs in February.

 

The pattern before that may be highly variable with brief shots of -10 anomaly arctic air interspersed with +3 type warm sectors in a generally WNW flow, in other words, clippers on parade. This would be a rather dry pattern for many with some lake effect squall opportunities. The warm spell will be massive for central-eastern regions and could involve rain/drizzle/fog into far northern plains states as well as northern New England, and an early snow melt in those regions and even into parts of nw to n/c ON and s MB except for possibility of major snowfall western MB into SK and MT.

analogs like 1954, 1985 and 1997 all had 70 degree readings in NYC during February...1930 also...1930 and 1985 share the record highest February max...

[Srain]

Winter Storm Potential February 8th-15th Thoughts:

 

The ensemble guidance remains in agreement that general Eastern trough with embedded short wave (Clipper system) will move across Canada along the Polar Jet and ridging controls the West in the short range.

 

As we head toward the medium range, changes begin to develop across the West as the upper ridge breaks down across the Great Basin and shifts E into the Mid West. Rich Pacific moisture begins streaming E from the EPAC and the sub tropical jet become active. A series of 500mb short waves dive S and meander over the NW Mexico/Arizona/Southern California Regions while a series of disturbances rotate under the base of a developing trough to our W and slide ENE providing clouds and perhaps some light rain chances early next week in the warmer sector with freezing rain chances further N as the Arctic boundary begins to retreat into Canada.

 

As the trough to our West deepens, a general unsettled pattern develops across the West Coast/Great Basin/Southern Rockies/Southern Plains as pressures fall and an increasing onshore Gulf flow becomes established. During the later half of next week the ensembles are in rather good agreement that a strong storm system will drop SSE from the Gulf of Alaska. This storm appears to have some colder air associated with it as it pulls Canadian air into the Great Basin. There are indications that a potent Winter Storm will begin to slowly develop and eject ENE along the southern stream and a clipper system rides ESE along a stagnant Polar jet across the Great Lakes into the NE. Heights falls across Alaska and a PNA Ridge develops off the Pacific NW flooding Western Canada with ‘warmer air’ while the meandering somewhat cold core upper low is energized by the noisy STJ. The time frame that is of concern would be near February 8^th, +/- a couple of days. The guidance continues to hint that some NW Atlantic blocking may occur near this time frame. This is a complex and complicated forecast due to the influence of the MJO, a Kelvin Wave as well as a changing pattern across the N Pacific and a tanking AO. As has been mentioned, there are indications that some chilly Canadian air will be dropping S in the mid February time frame. With Clipper systems streaming SE along the Polar jet and an active Southern Jet, potential arises for wintry precip from the Mid West on E.

[DaculaWeather]

Winter Storm Potential February 8th-15th Thoughts:

 

The ensemble guidance remains in agreement that general Eastern trough with embedded short wave (Clipper system) will move across Canada along the Polar Jet and ridging controls the West in the short range.

 

As we head toward the medium range, changes begin to develop across the West as the upper ridge breaks down across the Great Basin and shifts E into the Mid West. Rich Pacific moisture begins streaming E from the EPAC and the sub tropical jet become active. A series of 500mb short waves dive S and meander over the NW Mexico/Arizona/Southern California Regions while a series of disturbances rotate under the base of a developing trough to our W and slide ENE providing clouds and perhaps some light rain chances early next week in the warmer sector with freezing rain chances further N as the Arctic boundary begins to retreat into Canada.

 

As the trough to our West deepens, a general unsettled pattern develops across the West Coast/Great Basin/Southern Rockies/Southern Plains as pressures fall and an increasing onshore Gulf flow becomes established. During the later half of next week the ensembles are in rather good agreement that a strong storm system will drop SSE from the Gulf of Alaska. This storm appears to have some colder air associated with it as it pulls Canadian air into the Great Basin. There are indications that a potent Winter Storm will begin to slowly develop and eject ENE along the southern stream and a clipper system rides ESE along a stagnant Polar jet across the Great Lakes into the NE. Heights falls across Alaska and a PNA Ridge develops off the Pacific NW flooding Western Canada with ‘warmer air’ while the meandering somewhat cold core upper low is energized by the noisy STJ. The time frame that is of concern would be near February 8^th, +/- a couple of days. The guidance continues to hint that some NW Atlantic blocking may occur near this time frame. This is a complex and complicated forecast due to the influence of the MJO, a Kelvin Wave as well as a changing pattern across the N Pacific and a tanking AO. As has been mentioned, there are indications that some chilly Canadian air will be dropping S in the mid February time frame. With Clipper systems streaming SE along the Polar jet and an active Southern Jet, potential arises for wintry precip from the Mid West on E.

Thanks Steve... good stuff.

[ncwinterwxman]

I tend to agree with the EURO on the pattern going forward which would tend to indicate a track from the western Gulf Coast up the spine of the Appalachian Mountains into the interior NE states.  This would be one heck of a severe weather outbreak setup from the mid-south on up into the Ohio Valley...the long range GFS tends to be too noisy for my tastes   Good discussion...

Winter Storm Potential February 8th-15th Thoughts:

 

The ensemble guidance remains in agreement that general Eastern trough with embedded short wave (Clipper system) will move across Canada along the Polar Jet and ridging controls the West in the short range.

 

As we head toward the medium range, changes begin to develop across the West as the upper ridge breaks down across the Great Basin and shifts E into the Mid West. Rich Pacific moisture begins streaming E from the EPAC and the sub tropical jet become active. A series of 500mb short waves dive S and meander over the NW Mexico/Arizona/Southern California Regions while a series of disturbances rotate under the base of a developing trough to our W and slide ENE providing clouds and perhaps some light rain chances early next week in the warmer sector with freezing rain chances further N as the Arctic boundary begins to retreat into Canada.

 

As the trough to our West deepens, a general unsettled pattern develops across the West Coast/Great Basin/Southern Rockies/Southern Plains as pressures fall and an increasing onshore Gulf flow becomes established. During the later half of next week the ensembles are in rather good agreement that a strong storm system will drop SSE from the Gulf of Alaska. This storm appears to have some colder air associated with it as it pulls Canadian air into the Great Basin. There are indications that a potent Winter Storm will begin to slowly develop and eject ENE along the southern stream and a clipper system rides ESE along a stagnant Polar jet across the Great Lakes into the NE. Heights falls across Alaska and a PNA Ridge develops off the Pacific NW flooding Western Canada with ‘warmer air’ while the meandering somewhat cold core upper low is energized by the noisy STJ. The time frame that is of concern would be near February 8^th, +/- a couple of days. The guidance continues to hint that some NW Atlantic blocking may occur near this time frame. This is a complex and complicated forecast due to the influence of the MJO, a Kelvin Wave as well as a changing pattern across the N Pacific and a tanking AO. As has been mentioned, there are indications that some chilly Canadian air will be dropping S in the mid February time frame. With Clipper systems streaming SE along the Polar jet and an active Southern Jet, potential arises for wintry precip from the Mid West on E.

[Srain]

EXTENDED FORECAST DISCUSSION
NWS HYDROMETEOROLOGICAL PREDICTION CENTER COLLEGE PARK MD
157 AM EST SAT FEB 02 2013

VALID 12Z TUE FEB 05 2013 - 12Z SAT FEB 09 2013

IN ONE WAY OR ANOTHER...THE EASTERN HALF OF THE US WILL REMAIN
UNDER THE INFLUENCE OF A COLD VORTEX ANCHORED OVER EASTERN
CANADA...WITH A SERIES OF ALBERTA-TYPE CLIPPER SYSTEMS MIGRATING
INTO THE BASE OF THE TROUGH...CREATING MUCH IF NOT ALL OF THE
SENSIBLE WEATHER INTO DAY 5. WAS ABLE TO MAINTAIN VERY GOOD
CONTINUITY FROM THE PREVIOUS SURFACE GRAPHICS EVEN WITHOUT THE 12Z
GFS/GEFS GUIDANCE.

THE 1-12Z GFS/ECMWF OPERATIONALS GENERALLY ACCEPTED A STORM TRACK
THAT ARCS FROM THE DAKOTAS AND UPPER MISSISSIPPI VALLEY THROUGH
THE MIDWEST AND INTO THE MID ATLANTIC STATES...BEFORE EXITING INTO
THE WESTERN ATLANTIC OCEAN. THESE CLIPPERS WILL BE GENERATING
PERIODS OF LIGHT SNOWFALL ACROSS THEIR NORTHERN FLANKS AND
REINFORCING A CANADIAN AIRMASS INTO THE SOUTHERN PLAINS AND
SOUTHEAST IN THEIR WAKE. THE FLOW PATTERN TRANSITIONS AWAY FROM
THE CURRENT ONE...ON LATE DAY 5 INTO DAY 7 IN THE EAST...BUT NOT
BEFORE ONE LAST COASTAL WAVE MODIFIES ALONG ITS JOURNEY
EASTWARD...FROM THE MIDWEST AND OHIO VALLEY INTO THE WESTERN
ATLANTIC OCEAN.

IN A BROAD-BRUSHED SENSE...DAYS 5-7...MAY END UP BEING A BIGGER
WEATHER ISSUE IN THE WEST...SOUTHERN GREAT BASIN AND EVENTUALLY
THE CENTRAL...SOUTHERN ROCKIES AND SOUTH CENTRAL PLAINS RATHER
THAN THE EAST. IN THAT...AN AMPLIFYING PACIFIC TROUGH THAT SPLITS
WHILE MIGRATING INTO AND THROUGH THE CENTRAL GREAT BASIN AND THE
FOUR CORNERS AREA WILL GENERATE BROAD-SCALE LIFT AND USHER IN A
MUCH COLDER AND UNSTABLE AIRMASS INTO THE REGION. SEVERAL
MID-LEVEL SHORTWAVES EVENTUALLY EJECT NORTHEASTWARD OUT FROM THE
H5 TROUGH AND ACROSS THE NORTHERN ROCKIES AND NORTHERN HIGH PLAINS
STATES.

ANTICIPATE A GRADUAL SLOWDOWN OF THE UPPER TROUGH...WITH A
DEEPENING LEE SIDE TROUGH AND BROAD-SCALE UPSLOPE FLOW COMPONENT
TO TAKE SHAPE FROM EASTERN MONTANA...SOUTHWARD INTO WYOMING AND
COLORADO IN ADVANCE OF THE UPPER TROUGH. THIS WILL GENERATE A
SERIES OF SURFACE WAVES THAT WILL GENERATE LOCALLY MODERATE
PRECIPITATION ALONG THE CONTINENTAL DIVIDE...THEN EXIT THE ROCKIES
FOR THE PLAINS AND MIDWEST. A QUICK LOOK AT THE 2-00Z OPERATIONAL
ECMWF/GFS INDICATE A SLOWER...AND DEEPER SYSTEM THAN THE 1-12Z
ECMWF MEANS OVER THE WEST COAST AND GREAT BASIN...BETWEEN 8/00Z
AND 9/00Z.

THE DETAILS OF THE SPLITTING UPPER-LEVEL TROUGH ARE
INTRIGUING...WITH POTENTIAL FOR A CUTOFF H5 LOW TO FORM ALONG THE
SOUTHERN END OF THE TROUGH. THIS ADDS SOME UNCERTAINTY TO THE DAY
6-7 FORECAST FOR A PRECISE STORM TRACK TO EMERGE FROM THE CENTRAL
ROCKIES. 

VOJTESAK
 

[Srain]

Major Winter Storm Febraury 8th -12th Thoughts:

 

There continues to be a lot of uncertainty regarding the upcoming weekend and early next week as a long wave trough develops across the West. What we do know is a deep trough with a Potent Winter Storm will develop across the Great Basin and Intermountain West. In fact the HPC has so little confidence in the guidance, they have tasked a NOAA G-IV Winter RECON mission to fly the Pacific and sample the environment. Across the W, wintry conditions appear likely beginning Thursday as a potent storm system moves inland along the Pacific NW/British Columbia area and drop SSE and closes off near the California/Arizona/Mexico border with temps aloft expect to drop to the -30+ range as the cold core 500mb upper low forms. Due to lack of guidance continuity, the implications of how that storm ejects from the Great Basin is the main concern for the late weekend/early next week time frame. The HPC is mentioning this morning the similarity to a Spring like storm we tend to see in late March/early April meaning a wide spread severe weather event in the warm sector that extends from Eastern New Mexico/Texas/Oklahoma and portions of Kansas with wintry weather in the cold sector N of the Polar jet. The fly in the ointment is will there be phasing with yet another short wave riding the Polar jet across Southern Canada into the Northern Plains with the active southern jet stream storm which would tend to pull down cold air from the N and collide with warm moist Gulf air to the S. The Sub tropical jet appears to come into play as well as tropical forcing increasing across the Eastern Pacific energizing the Great Basis storm  We are in a somewhat zonal split flow pattern where cold air has retreated N with an active northern stream and a secondary active southern stream where this storm system will organize later this week. All in all a very active pattern is ahead and for much of the CONUS as rain chances are returning this week to the Gulf Coastal Regions with an active southern stream and the Pacific NW as the Gulf of Alaska storm moves inland. The finer details regarding the Medium Range forecast should become bit clearer later in the week as data from WSR scheduled to begin 06/0000 regarding next weekend  into early next week and the sensible weather we can expect.

 

 

EXTENDED FORECAST DISCUSSION
NWS HYDROMETEOROLOGICAL PREDICTION CENTER COLLEGE PARK MD
142 AM EST MON FEB 04 2013

VALID 12Z THU FEB 07 2013 - 12Z MON FEB 11 2013


DAYS 3-5...
OVERNIGHT SURFACE GRAPHICS WERE ABLE TO MAINTAIN VERY GOOD
CONTINUITY WITH A BLEND OF THE 3/12Z ECMWF AND ITS ENSEMBLE
MEANS...ALONG WITH SOME OF THE 3/12Z UKMET. THE 4/00Z GFS GETS TO
BE A FAST OUTLIER BY FRIDAY (DAY 4) WITH THE 'CLIPPER' RACING
THROUGH THE OHIO VALLEY AND OFFSHORE INTO THE WESTERN ATLANTIC.
THE 4/00Z UKMET-ECMWF WERE BETTER FITS TO THE MANUAL GRAPHICS AND
THE PATTERN EVOLVING VS THE 4/00Z GFS-CANADIAN.

WITH MUCH OF THE 4/00Z GUIDANCE IN...THERE IS PLENTY OF SUPPORT
FOR COMPLEX COASTAL WAVE DEVELOPMENT AND SECONDARY INTENSIFICATION
OF A SURFACE WAVE OFF THE IMMEDIATE COASTLINE (IN THE OUTER BANKS
AND BLOCK ISLAND CORRIDOR) ON FRIDAY AFTERNOON/EVENING. THE MANUAL
GRAPHICS CERTAINLY ARE NOT PERFECT PROGS...BUT I DID DRAW A SFC
LOW TRACK (AND INTERMEDIATE POSITION)...PASSING OVER THE BENCHMARK
BEFORE 9/00Z IN THE NEIGHBORHOOD OF 1004 MB AND DEEPENING TO 996MB
EAST OF HALIFAX NS AROUND 9/12Z. THIS INTERMEDIATE PROG (VALID
9/00Z) IS CLOSER TO THE 4/00Z UKMET FOR DEPTH BUT HONORS THE TRACK
OF THE 3/12Z ECMWF PACKAGE AND THE 4/00Z OPERATIONAL ECMWF. THE
DEEPEST SFC PRESSURE AT 983 MB AS IT ENTERS THE SW GULF OF MAINE
AFTER 9/00Z MIGHT BE OVERDONE...BUT THE TRENDS FROM YESTERDAY
SUPPORT ONE LAST CYCLONE (CLIPPER) BEFORE THE ARCTIC AIRMASS
RETREATS AWAY FROM THE EASTERN SEABOARD.

DAYS 6-7...    
THE MEDIUM RANGE GUIDANCE HAD A GOOD HANDLE ON THE WEST COAST
TROUGH AND MODERATELY-INTENSE CYCLONE EXITING THE SOUTH CENTRAL
ROCKIES NEXT WEEKEND. AS ENVISIONED A COUPLE OF DAYS AGO...THE
SYSTEM HAS SLOWED A TAD...BUT WILL SWEEP SOME PACIFIC ENERGY AND A
WEAK SURFACE REFLECTION ACROSS THE NORTHERN ROCKIES AND THROUGH
THE NORTH DAKOTA PLAINS BEFORE THIS NORTHERN END OF THE FRONT
WEAKENS IN NORTHERN MINNESOTA AND WESTERN ONTARIO.

THE MANUAL H5 TRACK FOR THIS SYSTEM DOWNSTREAM OF THE FRONT RANGE
WAS DRAWN WITH A 'BEST FIT' LINE FROM PUEBLO CO TO MINNEAPOLIS MN
GIVEN THE VARIABILITY IN TRACK AND SPEED. THE GFS IS THE MAIN
REASON THERE IS 'INTRODUCED UNCERTAINTY'. I CAN NOT REALLY FOLLOW
ITS RUN TO RUN ADJUSTMENTS...BUT THE H5 TRACK IS NOT FAR FROM THE
TRACK ENVISIONED FOR NEXT WEEKEND. THE WESTERN GOMEX SHOULD BE
WIDE OPEN AHEAD OF THIS CYCLONE.

THE ONE TREND THAT WILL NEED TO BEAR WATCHING...IS...HOW THE
INTENSE WEST-NORTHWESTERLY FLOW SURGING THROUGH THE 4 CORNERS AND
SOUTHERN DIVIDE REGION ON SATURDAY TRANSLATES DOWNSTREAM OVER THE
SOUTHERN HIGH PLAINS OF ERN NM/WRN TX LATER ON SATURDAY AFTERNOON
AND EVENING. IN SOME RESPECTS...THIS PACIFIC SYSTEM LOOKS MORE
LIKE A LATE MARCH/EARLY APRIL SYSTEM... WITH A WELL-DEFINED DRY
SLOT AND WARM ADVECTION WORKING NNEWD ACROSS THE TX PANHANDLE AND
SOUTH CENTRAL KANSAS...AND INTO THE H5 CYCLONE'S CIRCULATION. THIS
MAY END UP SHIFTING THE GULF MOISTURE EAST AND SOUTH OF THE COLD
FRONT INITIALLY...AND BRIEFLY LIMIT THE PHASING OF THE LOW-LEVEL
MOISTURE LIFTING ATOP THE COLD SECTOR OF THIS SYSTEM INVOF 40N
LATITUDE AND BETWEEN 94W-99W LONGITUDE. LIKEWISE..A DRIER EASTERLY
LOW-LEVEL FLOW IS ANTICIPATED TO BE WORKING INTO THIS SYSTEM ALONG
ITS NORTHERN PERIPHERY THROUGH EARLY SUNDAY. 

VOJTESAK

[nschiraldi]

New to the forum, but you guys have had some interesting discussions going on! Some ramblings...

 

The CFS extended is trending warmer, and this is line with low frequency based constructed analogs. One of the key reasons for the CFS extended warming is due to a coherent MJO signal coming out over the IO. This is consistent with my CFS lower tropospheric AAM forecast through March (http://www.atmos.albany.edu/student/nschiral/gwo.html#CFS). However, most of the statistical prediction methods (see Roundy's contingency analysis) are forecasting equal chances for warm and cold through late February and March.

 

The main reason for this is largely dependent on the amplitude of the MJO. Although some may think so, the MJO does not solicite a linear response in the atmosphere as a function amplitude. When the MJO gets above 2.5-3 sigma on the phase space, in a composite sense all bets are off. So, there is some risk that cold could return the to Eastern half of the CONUS however it doesn't seem like. It is more likely that cold would return briefly through a synoptic event.

 

A side note on ENSO:

Strong westerly wind bursts associated with the most recent MJO event has helped spark an oceanic kelvin wave. You can see it pretty nice in the TAO data (http://www.pmel.noaa.gov/tao/jsdisplay/). These oceanic kelvin waves are one of the driving forces of the ENSO system. If the mid March MJO event can maintain is structure out through the IO and into the E.Pacific there is a slight chance this oceanic Kelvin wave could amplify. As the Kelvin wave propagates Eastward towards S.America the warmer surface waters associated with it will be at the mercy of the trade winds, however should it form an oceanic front the ENSO picture could be more interesting than the consensus of La Nina across the board... Low probability but something to keep an eye on...

 

Nick

 

 

Looks like the trend is warmer

 

[am19psu]

Welcome to the board, Nick. Looking forward to your analysis in the future.

[DaculaWeather]

Yes, welcome! Good discussion, thanks for your insight! 

[donsutherland1]

February Update...

 

With the first week of February almost completed, I have no major changes from my thoughts for the month expressed in Message #535 in this thread. Briefly, the temperature anomalies shown from the teleconnection analogs were as follows:

 

 

The temperature anomalies for first three days of the month (NCEP's re-analysis charts don't go beyond February 3) were as follows:

 

 

To date, my lead analog (1967) remains in play. Hence, my confidence that the month will wind up on the cold side of normal, not necessarily extreme, and snowier than normal for the Mid-Atlantic, New England, and possibly Ohio Valley has increased. Recent runs of the ECMWF and the 2/5 12z run of the GFS don't undermine that growing confidence.

 

Moreover, repeated runs of the ensembles have indicated that the EPO should turn negative and possibly sharply negative as the calendar approaches mid-month. There has also been a growing signal for renewed blocking (Arctic Oscillation) in the medium-term, along with a continued neutral to somewhat positive PNA. In short, at least at this point in time, my February thoughts appear to remain on track.

 

All said, what a difference a year makes. At this point last year, February was already accumulating coast-to-coast warm anomalies en route to becoming the 16th warmest February on record (CONUS) and 5th warmest on record in the Northeast. At least in my opinion, the almost daily coatings for snow from fast-moving clipper systems is far better than last year's march through seemingly unending warmth.

 

February 3, 2013

[wxmx]

New to the forum, but you guys have had some interesting discussions going on! Some ramblings...

 

The CFS extended is trending warmer, and this is line with low frequency based constructed analogs. One of the key reasons for the CFS extended warming is due to a coherent MJO signal coming out over the IO. This is consistent with my CFS lower tropospheric AAM forecast through March (http://www.atmos.albany.edu/student/nschiral/gwo.html#CFS). However, most of the statistical prediction methods (see Roundy's contingency analysis) are forecasting equal chances for warm and cold through late February and March.

 

The main reason for this is largely dependent on the amplitude of the MJO. Although some may think so, the MJO does not solicite a linear response in the atmosphere as a function amplitude. When the MJO gets above 2.5-3 sigma on the phase space, in a composite sense all bets are off. So, there is some risk that cold could return the to Eastern half of the CONUS however it doesn't seem like. It is more likely that cold would return briefly through a synoptic event.

 

A side note on ENSO:

Strong westerly wind bursts associated with the most recent MJO event has helped spark an oceanic kelvin wave. You can see it pretty nice in the TAO data (http://www.pmel.noaa.gov/tao/jsdisplay/). These oceanic kelvin waves are one of the driving forces of the ENSO system. If the mid March MJO event can maintain is structure out through the IO and into the E.Pacific there is a slight chance this oceanic Kelvin wave could amplify. As the Kelvin wave propagates Eastward towards S.America the warmer surface waters associated with it will be at the mercy of the trade winds, however should it form an oceanic front the ENSO picture could be more interesting than the consensus of La Nina across the board... Low probability but something to keep an eye on...

 

Nick

Good post! I agree with your ENSO thoughts. I still think neutral is the more probable outcome, with an El Niño slightly more probable than it's female counterpart. Discussion about ENSO is ongoing in this thread, if you haven't checked it out.

[wxnewbie]

I'm fairly new to the forum and am curious as to what you guys think is driving the big discrepency in development of the midrange right now between the GFS and EMCWF.  Is it the MJO, as the GFS has it stalling and dying while the EMCWF has it speeding into phases 4/5? 

[GaWx]

I'm fairly new to the forum and am curious as to what you guys think is driving the big discrepency in development of the midrange right now between the GFS and EMCWF.  Is it the MJO, as the GFS has it stalling and dying while the EMCWF has it speeding into phases 4/5? 

In general, the GFS has had a pretty bad cold bias this winter and has often been too quick to bring in colder changes. OTOH, the Euro, if anything, has had a slight warm bias and has some tendency to not be progressive enough.

[donsutherland1]

With a Kocin-Uccellini (KU) snowstorm imminent across at least a large part of southern New England and perhaps the northern Mid-Atlantic, it is a good time to reflect back on possible early hints in the run-up to the winter. Needless to say, sample sizes are small, but the hint that the winter had at least some chance of a KU snowstorm were striking.

 

From Message #7 (11/24):

 

More recently, the AO averaged -1.514 during October. Since 1950, there were 8 prior cases during which the AO averaged -1.000 or below during October. 6/8 (75%) saw the winter AO average < 0.

From that pool of 8 cases, 4 saw the AO fall to -2.000 or below during the December 1-10 period, as is forecast to occur by a majority of ensemble members.

 

All four (1966, 1981, 2002, and 2009) saw the AO average < 0 during the winter. 3/4 (75%) of those winters experienced a KU snowstorm. The exception (winter 1981-82) saw a springtime KU snowstorm (the April 1982 blizzard).

 

From Message #25 (11/26) several major blocking patterns similar to what ultimately unfolded during winter 2012-13 were highlighted. The relevant text:

 

Recent examples include the blocking regimes of 2009-10 and 2010-11. The following severe blocking episodes (minimum AO value of -3.000 or below) began in late November/early December (11/20-12/10) following a blocky October (monthly AO of -025 or below):

December 7, 1966-January 11, 1967: 36 days
December 7, 1981-January 12, 1982: 37 days
November 29, 2009-January 15, 2010: 48 days
December 3, 2010-January 15, 2011: 44 days

 

Winter 2012-13 Case:

October Mean AO Value: -1.514

Block: November 24, 2012 through January 2, 2013; Duration: 40 days

Lowest Value: -3.902, December 8, 2012

 

After what seemed like a death march through a barren desert of warmth and then dry, cold—anything but significant snowfall—1967, one of the above-mentioned blocking cases, surged to the head of the proverbial pack as my lead analog for February.

 

From Message #535 (January 22):

 

Based on ENSO (neutral to borderline La Niña conditions for February and the teleconnections into early February/weight given to some of the past years for teleconnections similar to those of this winter), the most persistent teleconnection analog for February is 1967…

 

In terms of snowfall, February will probably prove to be the snowiest month of the winter. Snowfall in the Middle Atlantic and New England regions and possibly Ohio Valley could be above normal.

 

1967 featured a KU snowstorm during the February 5-8 timeframe.

 

Barring radical changes in the modeling, a KU snowstorm appears highly likely for southern New England. In some part of the region, snowfall amounts could approach historic proportions if some of the guidance, including the ECMWF, proves accurate. Heavy snowfall could also extend into the northern Mid-Atlantic (northern New Jersey, southeast New York State and across Long Island).

 

If some of the early hints, including the unseasonable early snowstorm in the NYC metro area, prove reliable, this storm likely will not bring the last snowfall to the Middle Atlantic and New England areas. From Message #6:

 

To date, November 2012 has seen 4.7” snowfall in New York City. There were six such cases since 1869: 1882, 1892, 1896, 1898, 1938, and 1989. 5/6 (83%) saw an additional 24.5” or more of snow accumulate during the season and 4/6 (67%) saw 30” or more additional snow. The single exception was winter 1989-90, which came to an abrupt end after a cold, snowy start.

 

Even if the 2/7 0z ECMWF verifies for the New York City area, seasonal snowfall is not likely to reach the levels cited above. Hence, should such information prove accurate, one could look for additional snowfalls, even if there is a pause for a time. Indeed, March 1967 also proved very snowy in such cities as New York and Boston.

 

The latest guidance shows that the potential is there. On the ensemble guidance, one finds the EPO forecast to go negative through at least the third week in February. The guidance has also come into stronger agreement that blocking (AO-) will unfold. If one also takes a look at the objective analogs for the 2/7 0z run of the GFS ensembles, the lead analog for centered on February 17 is February 12, 2006. Recent operational runs of the GFS have hinted at the possibility of above normal snowfall in the Ohio Valley and possibly eastward.

 

In sum, after a long sleep, winter has awakened.

[Kaner587]

With a Kocin-Uccellini (KU) snowstorm imminent across at least a large part of southern New England and perhaps the northern Mid-Atlantic, it is a good time to reflect back on possible early hints in the run-up to the winter. Needless to say, sample sizes are small, but the hint that the winter had at least some chance of a KU snowstorm were striking.

 

From Message #7 (11/24):

 

More recently, the AO averaged -1.514 during October. Since 1950, there were 8 prior cases during which the AO averaged -1.000 or below during October. 6/8 (75%) saw the winter AO average < 0.

From that pool of 8 cases, 4 saw the AO fall to -2.000 or below during the December 1-10 period, as is forecast to occur by a majority of ensemble members.

 

All four (1966, 1981, 2002, and 2009) saw the AO average < 0 during the winter. 3/4 (75%) of those winters experienced a KU snowstorm. The exception (winter 1981-82) saw a springtime KU snowstorm (the April 1982 blizzard).

 

From Message #25 (11/26) several major blocking patterns similar to what ultimately unfolded during winter 2012-13 were highlighted. The relevant text:

 

Recent examples include the blocking regimes of 2009-10 and 2010-11. The following severe blocking episodes (minimum AO value of -3.000 or below) began in late November/early December (11/20-12/10) following a blocky October (monthly AO of -025 or below):

December 7, 1966-January 11, 1967: 36 days

December 7, 1981-January 12, 1982: 37 days

November 29, 2009-January 15, 2010: 48 days

December 3, 2010-January 15, 2011: 44 days

 

Winter 2012-13 Case:

October Mean AO Value: -1.514

Block: November 24, 2012 through January 2, 2013; Duration: 40 days

Lowest Value: -3.902, December 8, 2012

 

After what seemed like a death march through a barren desert of warmth and then dry, cold—anything but significant snowfall—1967, one of the above-mentioned blocking cases, surged to the head of the proverbial pack as my lead analog for February.

 

From Message #535 (January 22):

 

Based on ENSO (neutral to borderline La Niña conditions for February and the teleconnections into early February/weight given to some of the past years for teleconnections similar to those of this winter), the most persistent teleconnection analog for February is 1967…

 

In terms of snowfall, February will probably prove to be the snowiest month of the winter. Snowfall in the Middle Atlantic and New England regions and possibly Ohio Valley could be above normal.

 

1967 featured a KU snowstorm during the February 5-8 timeframe.

 

Barring radical changes in the modeling, a KU snowstorm appears highly likely for southern New England. In some part of the region, snowfall amounts could approach historic proportions if some of the guidance, including the ECMWF, proves accurate. Heavy snowfall could also extend into the northern Mid-Atlantic (northern New Jersey, southeast New York State and across Long Island).

 

If some of the early hints, including the unseasonable early snowstorm in the NYC metro area, prove reliable, this storm likely will not bring the last snowfall to the Middle Atlantic and New England areas. From Message #6:

 

To date, November 2012 has seen 4.7” snowfall in New York City. There were six such cases since 1869: 1882, 1892, 1896, 1898, 1938, and 1989. 5/6 (83%) saw an additional 24.5” or more of snow accumulate during the season and 4/6 (67%) saw 30” or more additional snow. The single exception was winter 1989-90, which came to an abrupt end after a cold, snowy start.

 

Even if the 2/7 0z ECMWF verifies for the New York City area, seasonal snowfall is not likely to reach the levels cited above. Hence, should such information prove accurate, one could look for additional snowfalls, even if there is a pause for a time. Indeed, March 1967 also proved very snowy in such cities as New York and Boston.

 

The latest guidance shows that the potential is there. On the ensemble guidance, one finds the EPO forecast to go negative through at least the third week in February. The guidance has also come into stronger agreement that blocking (AO-) will unfold. If one also takes a look at the objective analogs for the 2/7 0z run of the GFS ensembles, the lead analog for centered on February 17 is February 12, 2006. Recent operational runs of the GFS have hinted at the possibility of above normal snowfall in the Ohio Valley and possibly eastward.

 

In sum, after a long sleep, winter has awakened.

amazing post don. 

[Harry]

With a Kocin-Uccellini (KU) snowstorm imminent across at least a large part of southern New England and perhaps the northern Mid-Atlantic, it is a good time to reflect back on possible early hints in the run-up to the winter. Needless to say, sample sizes are small, but the hint that the winter had at least some chance of a KU snowstorm were striking.

 

From Message #7 (11/24):

 

More recently, the AO averaged -1.514 during October. Since 1950, there were 8 prior cases during which the AO averaged -1.000 or below during October. 6/8 (75%) saw the winter AO average < 0.

From that pool of 8 cases, 4 saw the AO fall to -2.000 or below during the December 1-10 period, as is forecast to occur by a majority of ensemble members.

 

All four (1966, 1981, 2002, and 2009) saw the AO average < 0 during the winter. 3/4 (75%) of those winters experienced a KU snowstorm. The exception (winter 1981-82) saw a springtime KU snowstorm (the April 1982 blizzard).

 

From Message #25 (11/26) several major blocking patterns similar to what ultimately unfolded during winter 2012-13 were highlighted. The relevant text:

 

Recent examples include the blocking regimes of 2009-10 and 2010-11. The following severe blocking episodes (minimum AO value of -3.000 or below) began in late November/early December (11/20-12/10) following a blocky October (monthly AO of -025 or below):

December 7, 1966-January 11, 1967: 36 days

December 7, 1981-January 12, 1982: 37 days

November 29, 2009-January 15, 2010: 48 days

December 3, 2010-January 15, 2011: 44 days

 

Winter 2012-13 Case:

October Mean AO Value: -1.514

Block: November 24, 2012 through January 2, 2013; Duration: 40 days

Lowest Value: -3.902, December 8, 2012

 

After what seemed like a death march through a barren desert of warmth and then dry, cold—anything but significant snowfall—1967, one of the above-mentioned blocking cases, surged to the head of the proverbial pack as my lead analog for February.

 

From Message #535 (January 22):

 

Based on ENSO (neutral to borderline La Niña conditions for February and the teleconnections into early February/weight given to some of the past years for teleconnections similar to those of this winter), the most persistent teleconnection analog for February is 1967…

 

In terms of snowfall, February will probably prove to be the snowiest month of the winter. Snowfall in the Middle Atlantic and New England regions and possibly Ohio Valley could be above normal.

 

1967 featured a KU snowstorm during the February 5-8 timeframe.

 

Barring radical changes in the modeling, a KU snowstorm appears highly likely for southern New England. In some part of the region, snowfall amounts could approach historic proportions if some of the guidance, including the ECMWF, proves accurate. Heavy snowfall could also extend into the northern Mid-Atlantic (northern New Jersey, southeast New York State and across Long Island).

 

If some of the early hints, including the unseasonable early snowstorm in the NYC metro area, prove reliable, this storm likely will not bring the last snowfall to the Middle Atlantic and New England areas. From Message #6:

 

To date, November 2012 has seen 4.7” snowfall in New York City. There were six such cases since 1869: 1882, 1892, 1896, 1898, 1938, and 1989. 5/6 (83%) saw an additional 24.5” or more of snow accumulate during the season and 4/6 (67%) saw 30” or more additional snow. The single exception was winter 1989-90, which came to an abrupt end after a cold, snowy start.

 

Even if the 2/7 0z ECMWF verifies for the New York City area, seasonal snowfall is not likely to reach the levels cited above. Hence, should such information prove accurate, one could look for additional snowfalls, even if there is a pause for a time. Indeed, March 1967 also proved very snowy in such cities as New York and Boston.

 

The latest guidance shows that the potential is there. On the ensemble guidance, one finds the EPO forecast to go negative through at least the third week in February. The guidance has also come into stronger agreement that blocking (AO-) will unfold. If one also takes a look at the objective analogs for the 2/7 0z run of the GFS ensembles, the lead analog for centered on February 17 is February 12, 2006. Recent operational runs of the GFS have hinted at the possibility of above normal snowfall in the Ohio Valley and possibly eastward.

 

In sum, after a long sleep, winter has awakened.

 

Nice work Don..

 

Unfortunately the 67 analog failed to deliver the goods here ( like it did in Jan 67 aka Chicago blizzard that dumped 28.6" inches here ) unlike the northeast. Oh well.

 

Enjoy the snowstorm.