October 2013 pattern and discussion

[Jon]

Noticed the euro is close to a weak nino by early winter. This will be interesting to watch unfold. This combined with cold and snow bulid up over the NH in October usually means good things. There are some unfavorable things to consider as well, such as the QBO. Overall, I think the SST's over october have trended much more favorably in the atlantic and pacific (specifically the PDO regions and NAO regions). One thing I have noticed through several years of researching winter forecast analogs, is the trends over the late fall are much more important than the snapshot of a global SST map in early fall, which is what is commonly used in winter forecasts.

 

 

CFSv2 using today's init conditions, not too shabby.

[mackerel_sky]

I am a little concerned with our current pattern going into winter . In regards to these very dry frontal passages and lack of gulf moisture with these cold fronts.if we don't get more moisture aroun to interact with these cold shots keep coming on down the road, the only winners will be the NC/TN mountains this winter?

[FallsLake]

 In places like Atlanta and much of the SE US, it usually only takes one significant winter storm to put them well over the average annual S/IP or ZR. So, even without a persistent subtropical jet or a cold winter, much of the SE US can still get lucky and do well vs. averages with just one freak storm. More often than not, places like Atlanta will get only one sig winter storm, if any, in a typical winter although on occasion they get two and in very rare cases 3-4.

That's the problem with snow averages. My area averages around 7 inches a year. This average comes from many years where we get little snow to years where we get a good amount (well over 10"). On the high and lowes; there have been years with a trace and a year with 25". So basically there is a difference between average and what is expected (..which we never have any idea).

[1300m]

RAH long range discussing the possibility that lows Friday night might drop further than currently forecasted.

 

THURSDAY THROUGH SUNDAY: A SHORTWAVE TROUGH AND SUBSEQUENT THIRD

COLD FRONT WILL MOVE THROUGH CENTRAL NC THURSDAY NIGHT...WITH AND

INCREASE IN LOW TO MID LEVEL MOISTURE...MAY BRING AN INCREASE IN

CLOUD COVER AND KEEP TEMPS FROM DROPPING BELOW THE MID 30S IN THE NW

THURSDAY NIGHT. WITH THE COLD AIR IN PLACE...HIGHS ON THURSDAY

EXPECTED TO BE IN THE UPPER 50S TO LOW 60S. BEHIND THE LATEST COLD

FRONT...POLAR HIGH PRESSURE WILL BUILD INTO THE AREA...BRINGING WITH

IT CLEARING SKIES...LIGHT OVERNIGHT WINDS (ALLOWING FOR IDEAL

RADIATIONAL COOLING CONDITIONS) AND THE COLDEST TEMPERATURES OF THE

SEASON. THE HIGHLIGHT OF THIS PERIOD WILL BE THE LOWS FRIDAY

NIGHT/SATURDAY MORNING AS THE HIGH IS CENTERED OVERHEAD...WITH THE

POTENTIAL FOR SOME UPPER 20S OVER THE NORTHWEST HALF OF THE AREA TO

MID 30S SE. WITH THESE TEMPS COMES AN INCREASING PROBABILITY OF THE

FIRST FREEZE OF THE SEASON FOR AREAS ALONG AND WEST OF I-95.

INTERESTING TO NOTE...MODEL FORECASTED LOW LEVEL THICKNESS VALUES

ARE IN THE 1310 METER RANGE...WHICH WOULD SUGGEST LOWS IN THE LOW TO

MID 20S...BUT WITH MODEL UNCERTAINTY THIS FAR OUT WILL WAIT A BIT TO

SEE HOW THAT FORECAST EVOLVES WITH TIME. AS WAS MENTIONED IN THE

PREVIOUS DISCUSSION...THE RECORD LOW AT RDU FOR THE 26TH IS 27...

AND AT GSO IS 23 DEGREES. HIGH TEMPS FRIDAY AND SATURDAY EXPECTED TO

BE IN THE MID TO UPPER 50S ACROSS THE NORTHERN TWO-THIRDS OF THE

AREA...TO LOW 60S ACROSS THE SOUTH...INCREASING TO THE LOW TO MID

60S FOR SUNDAY. OVERNIGHT LOWS SHOULD GRADUALLY REBOUND THROUGH

SUNDAY NIGHT...TO THE MID 30S NW TO LOW 40S SE.

 

 

I know how this is going to sound, but while I agree that temperatures in the upper 20s are likely on Friday night, the reasoning I've highlighted from RAH doesn't cut the mustard for me. I know the principal researcher who introduced the partial thickness methodology - Kermit Keeter - and he has actually told the guys at the NWS-RAH that using partial thicknesses to predict low temperatures isn't a proper use of the method.

 

Physically, it doesn't make sense. On a clear, calm night the PBL height is only ~50mb above the ground. Looking at thicknesses all the way up to 850mb doesn't make sense because only the air mass in the lowest 50mb is affecting the nighttime temperature. That's just a pet peeve of mine but I digress.

 

The most influential variables that impact the low are: clouds, winds, soil moisture, the rare snowpack, and of course the dewpoints. All of those factors minus a snowpack look favorable for the temperature to rapidly drop after sunset on Friday night, and will likely result in many areas across NC experiencing a solid 3 to 6 hour window at or below freezing.

[DaculaWeather]

I know how this is going to sound, but while I agree that temperatures in the upper 20s are likely on Friday night, the reasoning I've highlighted from RAH doesn't cut the mustard for me. I know the principal researcher who introduced the partial thickness methodology - Kermit Keeter - and he has actually told the guys at the NWS-RAH that using partial thicknesses to predict low temperatures isn't a proper use of the method.

 

Physically, it doesn't make sense. On a clear, calm night the PBL height is only ~50mb above the ground. Looking at thicknesses all the way up to 850mb doesn't make sense because only the air mass in the lowest 50mb is affecting the nighttime temperature. That's just a pet peeve of mine but I digress.

 

The most influential variables that impact the low are: clouds, winds, soil moisture, the rare snowpack, and of course the dewpoints. All of those factors minus a snowpack look favorable for the temperature to rapidly drop after sunset on Friday night, and will likely result in many areas across NC experiencing a solid 3 to 6 hour window at or below freezing.

Good info! Thanks! :-)

[Wow]

I am a little concerned with our current pattern going into winter . In regards to these very dry frontal passages and lack of gulf moisture with these cold fronts.if we don't get more moisture aroun to interact with these cold shots keep coming on down the road, the only winners will be the NC/TN mountains this winter?

 

No STJ activity at the moment with fronts dropping from Canada but that looks to change if the models are correct over the next couple of weeks.  And long term if the ENSO forecasts are correct.

[FallsLake]

I know how this is going to sound, but while I agree that temperatures in the upper 20s are likely on Friday night, the reasoning I've highlighted from RAH doesn't cut the mustard for me. I know the principal researcher who introduced the partial thickness methodology - Kermit Keeter - and he has actually told the guys at the NWS-RAH that using partial thicknesses to predict low temperatures isn't a proper use of the method.

 

Physically, it doesn't make sense. On a clear, calm night the PBL height is only ~50mb above the ground. Looking at thicknesses all the way up to 850mb doesn't make sense because only the air mass in the lowest 50mb is affecting the nighttime temperature. That's just a pet peeve of mine but I digress.

 

The most influential variables that impact the low are: clouds, winds, soil moisture, the rare snowpack, and of course the dewpoints. All of those factors minus a snowpack look favorable for the temperature to rapidly drop after sunset on Friday night, and will likely result in many areas across NC experiencing a solid 3 to 6 hour window at or below freezing.

I agree -- great info.

I think there maybe some disagreement within the RAH office as well. For the last couple of days the day shift lowers the forecasted low temp a little and then the night shift raises it a little.

[1300m]

I agree -- great info.

I think there maybe some disagreement within the RAH office as well. For the last couple of days the day shift lowers the forecasted low temp a little and then the night shift raises it a little.

 

Great insight. I know this is banter more than weather, but Falls you hit it right on the head. I can personally attest that there are at least two factions in the office. Badgett and Hartfield are probably the two most opposite and I know who I'd put my money on every time

 

P.S. I'll also say that one of those two is the champion behind why the office uses 1000-850mb thicknesses for nighttime low forecasting, and their not the one my money is on lol.

[DaculaWeather]

Having the same issues here in Atlanta:

 

AFTER THE COLD FRONT MOVES THROUGH ON FRIDAY...GOOD CAA WILL TAKE
PLACE. SATURDAY MORNING IS STILL EXPECTED TO BE THE COLDEST...AS
HIGH PRESSURE WILL BE DIRECTLY OVERHEAD WITH CLEAR SKIES AND CALM
WINDS. MODELS HAVE CONTINUED TO DROP THE TEMPERATURES A DEGREE OR SO
WITH EACH RUN...BUT AM HESITANT TO GO THAT LOW. EVEN WITH THE
SLIGHTLY WARMER THAN GUIDANCE TEMPS...PATCHY FROST IS NOW POSSIBLE
OVER HALF OF THE CWFA. IN ADDITION...SOME PATCHY SPOTS AT OR BELOW
FREEZING ARE POSSIBLE ACROSS THE NORTH.

[buckeyefan1]

In my experience it takes a persistent pattern most times to get a multiple.  I.E. split flow with blocking and a wet southern stream.  Getting a big event in Jan. then a mild Feb. and another event in March is harder to do, lol.  I like the two or three in a week to 10 days play, where it's cold the whole time, and you get frozen precip on top of old ice.

  I'd be curious how many multiple storm year storms came in clusters as opposed to spread over months.   Whatever, I'm ready for my long awaited back to back sleet extravaganzas.

  But I need rain first..... it won't sleet, if it won't rain. T

 

I would love to see the bolded as we head into Dec  

 

No STJ activity at the moment with fronts dropping from Canada but that looks to change if the models are correct over the next couple of weeks.  And long term if the ENSO forecasts are correct.

 

 

 

CAE's throwing around one of the "f" words for the counties to my north    

 

 

.LONG TERM /FRIDAY THROUGH MONDAY/...

MODELS ARE IN GOOD AGREEMENT THROUGH THE WEEKEND WITH SOME

DIVERGENCE IN SOLUTIONS AT THE BEGINNING OF NEXT WEEK. UPPER LEVEL

TROUGH WILL PUSH EAST OF THE REGION FRIDAY MORNING WITH HIGH

PRESSURE...ALONG WITH ADDITIONAL COLD AIR ADVECTION...BUILDING IN

DURING THE AFTERNOON. THE HIGH WILL MOVE THROUGH THE AREA DURING

THE DAY SATURDAY AND OFFSHORE SATURDAY NIGHT. DURING THIS TIME

SKIES WILL BE MOSTLY CLEAR WITH EXCELLENT RADIATIONAL COOLING

CONDITIONS OVERNIGHT. FROST REMAIN POSSIBLE FRIDAY AND SATURDAY

NIGHTS...HOWEVER CONFIDENCE ATTM IS TOO LOW TO MENTION AS

TEMPERATURE GUIDANCE CONTINUES TO ADJUST WITH RUN TO RUN CHANGES.

CURRENTLY THE BEST CHANCE APPEARS TO BE FROM THE LANCASTER AREA TO

AROUND NEWBERRY. ANOTHER WEAK FRONTAL BOUNDARY WILL CROSS THE

REGION ON SUNDAY...HOWEVER THIS FEATURE WILL AGAIN BE STARVED FOR

MOISTURE AND DYNAMICS RESULTING IN NO MENTION OF SHOWERS.

TEMPERATURES THROUGH THE LONG TERM WILL BE BELOW NORMAL.

[DaculaWeather]

I would love to see the bolded as we head into Dec  

 

 

 

CAE's throwing around one of the "f" words for the counties to my north  

 

 

.LONG TERM /FRIDAY THROUGH MONDAY/...

MODELS ARE IN GOOD AGREEMENT THROUGH THE WEEKEND WITH SOME

DIVERGENCE IN SOLUTIONS AT THE BEGINNING OF NEXT WEEK. UPPER LEVEL

TROUGH WILL PUSH EAST OF THE REGION FRIDAY MORNING WITH HIGH

PRESSURE...ALONG WITH ADDITIONAL COLD AIR ADVECTION...BUILDING IN

DURING THE AFTERNOON. THE HIGH WILL MOVE THROUGH THE AREA DURING

THE DAY SATURDAY AND OFFSHORE SATURDAY NIGHT. DURING THIS TIME

SKIES WILL BE MOSTLY CLEAR WITH EXCELLENT RADIATIONAL COOLING

CONDITIONS OVERNIGHT. FROST REMAIN POSSIBLE FRIDAY AND SATURDAY

NIGHTS...HOWEVER CONFIDENCE ATTM IS TOO LOW TO MENTION AS

TEMPERATURE GUIDANCE CONTINUES TO ADJUST WITH RUN TO RUN CHANGES.

CURRENTLY THE BEST CHANCE APPEARS TO BE FROM THE LANCASTER AREA TO

AROUND NEWBERRY. ANOTHER WEAK FRONTAL BOUNDARY WILL CROSS THE

REGION ON SUNDAY...HOWEVER THIS FEATURE WILL AGAIN BE STARVED FOR

MOISTURE AND DYNAMICS RESULTING IN NO MENTION OF SHOWERS.

TEMPERATURES THROUGH THE LONG TERM WILL BE BELOW NORMAL.

They should be BANNED!!! :-)

[CandymanColumbusGA]

I started mentioning on Sunday about the possibility of frost in some of the traditionally cooler spots in my area. The thing I'm REALLY not looking forward to is the rain on Halloween... I'm not going to be the most popular person when I show that this weekend.

[FLweather]

I started mentioning on Sunday about the possibility of frost in some of the traditionally cooler spots in my area. The thing I'm REALLY not looking forward to is the rain on Halloween... I'm not going to be the most popular person when I show that this weekend.

 

I seen on wxsouth fb that the potential is there for a wet halloween storm. With additional engery coming out the nw and what is the cutoff low near the west coast. I know its too early to be nit picky but that cutoff looks to be tied to the southern stream flow so if it works out than possibly seeing some type of cutoff low here in the SE with a good moisture flow up the EC.

[Met1985]

First freeze for the mountains on the way.

AVERY-MADISON-YANCEY-MITCHELL-SWAIN-HAYWOOD-BUNCOMBE-GRAHAM-NORTHERN JACKSON-MACON-SOUTHERN JACKSON-TRANSYLVANIA-HENDERSON-CALDWELL MOUNTAINS-BURKE MOUNTAINS-MCDOWELL MOUNTAINS-RUTHERFORD MOUNTAINS-POLK MOUNTAINS-INCLUDING THE CITIES OF...NEWLAND...SPRUCE PINE...BRYSON CITY...WAYNESVILLE...ASHEVILLE...SYLVA...FRANKLIN...BREVARD...HENDERSONVILLE403 PM EDT TUE OCT 22 2013...FREEZE WATCH IN EFFECT FROM LATE WEDNESDAY NIGHT THROUGHTHURSDAY MORNING......FREEZE WATCH IS CANCELLED...CORRECTIONTHE NATIONAL WEATHER SERVICE IN GREENVILLE-SPARTANBURG HAS ISSUEDA FREEZE WATCH...WHICH IS IN EFFECT FROM LATE WEDNESDAY NIGHTTHROUGH THURSDAY MORNING. THE FREEZE WATCH HAS BEEN CANCELLED.* LOCATIONS...THE NORTH CAROLINA MOUNTAINS* TEMPERATURES...MINIMUM TEMPERATURES WILL RANGE FROM THE UPPER  20S TO LOWER 30S.

[jburns]

First freeze for the mountains on the way.

AVERY-MADISON-YANCEY-MITCHELL-SWAIN-HAYWOOD-BUNCOMBE-GRAHAM-

NORTHERN JACKSON-MACON-SOUTHERN JACKSON-TRANSYLVANIA-HENDERSON-

CALDWELL MOUNTAINS-BURKE MOUNTAINS-MCDOWELL MOUNTAINS-

RUTHERFORD MOUNTAINS-POLK MOUNTAINS-

INCLUDING THE CITIES OF...NEWLAND...SPRUCE PINE...BRYSON CITY...

WAYNESVILLE...ASHEVILLE...SYLVA...FRANKLIN...BREVARD...

HENDERSONVILLE

403 PM EDT TUE OCT 22 2013

...FREEZE WATCH IN EFFECT FROM LATE WEDNESDAY NIGHT THROUGH

THURSDAY MORNING...

...FREEZE WATCH IS CANCELLED...CORRECTION

THE NATIONAL WEATHER SERVICE IN GREENVILLE-SPARTANBURG HAS ISSUED

A FREEZE WATCH...WHICH IS IN EFFECT FROM LATE WEDNESDAY NIGHT

THROUGH THURSDAY MORNING. THE FREEZE WATCH HAS BEEN CANCELLED.

* LOCATIONS...THE NORTH CAROLINA MOUNTAINS

* TEMPERATURES...MINIMUM TEMPERATURES WILL RANGE FROM THE UPPER

20S TO LOWER 30S.

 

Clear as mud.  Looks like they have legalized marijuana at GSP.

[dsaur]

Well, when you are watching for something to freeze, but it starts to boil instead, you cancel the avid watching   What I'm watching for is rain, and it has stopped raining around here since early summer.  By induction...solid to vapour/liquid to solid I'm hoping if I watch for rain, I'll get sleet instead...but for right now, rain will do.  T

[Met1985]

 

Clear as mud.  Looks like they have legalized marijuana at GSP.

Lol awesome! Ya I noticed that also. I was like WTH.

[BullCityWx]

The GFS is showing lows in the 20's on Saturday morning for most of the piedmont of NC and northwestern SC.

[1300m]

The GFS is showing lows in the 20's on Saturday morning for most of the piedmont of NC and northwestern SC.

 

Looking at the projected dewpoints down in the 25-27F range by 00z on Saturday along with the synoptic pattern, I think the majority of the Carolinas will have lows in the 20s. Most of the ASOS stations will probably be in the 26-29F range (from west to east), but some sheltered, low lying and rural areas (especially in the western piedmont) could dip even a degree or two lower than that.

 

For the majority of the Carolinas there could be a good 3-6 hour window at or below freezing - very impressive!

 

P.S. Should clarify that I'm roughly talking from I-95 west. Areas in the coastal plains will still likely get down into the 30-32F range.

[Wow]

Chilly Sat morning:

 

[FallsLake]

Halloween is the one time of the year where I hope for dry (storm-less) weather; I have kids that Trick-or-Treat. The LR models have been hinting at some sort of rain event around that time for many days now. The latest 12z GFS continues to show rain for somebody. I think this is going to be a timing issue where some will get wet and others will escape. But this should become more apparent by Sunday.    

[1300m]

RAH latest discussion only further proves what I was saying earlier - the correlation between partial thicknesses and nighttime temperatures is weak, and doesn't have any added value to looking at the typical variables associated with low forecasting.

 

Compare today's discussion:

 

WITH THICKNESSES NEAR 1300 TEMPERATURES HAVE THE POTENTIAL TO PLUNGE INTO THE UPPER 20S...ESPECIALLY IN THE RURAL COLD AREAS.

 

With the 10/21 afternoon discussion of 1000-850mb thicknesses:

 

INTERESTING TO NOTE...MODEL FORECASTED LOW LEVEL THICKNESS VALUES ARE IN THE 1310 METER RANGE...WHICH WOULD SUGGEST LOWS IN THE LOW TO MID 20S...

 

According to this, 1300m (hey, that's me!) correlates to upper 20s, while 1310 range is low to mid 20s. Call me crazy, but I thought colder air was more dense, thus making the column of air more compact, thus a lower thickness. The above discrepancy is flawed because 1) a 10m difference in low level thicknesses isn't going to make a 5+ degree difference in the temperature, and 2) higher thickness is the result of warmer air, not colder.  

 

I think this proves that the way RAH uses this for low forecasting has no added skill over the fundamentals, and doesn't even remain consistent from one discussion/forecaster to the next.

 

Just my musings on a boring afternoon...

[DCMetroWinston]

WXII is now saying highs will stay in the 40's on Friday in the Triad. That would be awesome!

[Wow]

Looks like we're going to get a bit of a reprieve after this cold shot with the -NAO flipping positive and the PNA falling back to near neutral and pulling us back to near, or slightly above normal temps.  

[FLweather]

RAH latest discussion only further proves what I was saying earlier - the correlation between partial thicknesses and nighttime temperatures is weak, and doesn't have any added value to looking at the typical variables associated with low forecasting.

 

Compare today's discussion:

 

With the 10/21 afternoon discussion of 1000-850mb thicknesses:

 

According to this, 1300m (hey, that's me!) correlates to upper 20s, while 1310 range is low to mid 20s. Call me crazy, but I thought colder air was more dense, thus making the column of air more compact, thus a lower thickness. The above discrepancy is flawed because 1) a 10m difference in low level thicknesses isn't going to make a 5+ degree difference in the temperature, and 2) higher thickness is the result of warmer air, not colder.  

 

I think this proves that the way RAH uses this for low forecasting has no added skill over the fundamentals, and doesn't even remain consistent from one discussion/forecaster to the next.

 

Just my musings on a boring afternoon...

 

Thanks for sharing... I can see that is a pet peave for you. Though it does make alot more sense to forecast off of other factors instead of thickness alone. Even if you have a cold column there is always something to hender the drop or allow for colder temps. Espeically perfect conditions for raditional cooling.

WXII is now saying highs will stay in the 40's on Friday in the Triad. That would be awesome!

 

Yeah even here 50 maybe a struggle. Needless to say it will be enjoyable Friday cold and blustery.

[FallsLake]

6z GFS still showing rain for many across the SE on Halloween. If this holds up this would be a great job by the model to verify a stormy pattern at over 10 days out. **but I'm really hoping it's wrong or at least the timing is wrong.  

[DCMetroWinston]

 

Larry Cosgrove: 

Yes, there will be a major storm affecting the central and eastern two-thirds of the U.S. around Halloween. ..... Pay attention to this storm; there may be some wet snow issues in the Upper Midwest and Great Lakes, but the threat for severe thunderstorms and tornadoes seems to be the main concern here. And yes, the mean 500MB trough will be deep enough to chill down the eastern two-thirds of the U.S. in early November.

[metalicwx366]

Where does Larry Cosgrove see it getting cold again at on any of the models? I see the storm, not the cold.

[Brick Tamland]

6z GFS still showing rain for many across the SE on Halloween. If this holds up this would be a great job by the model to verify a stormy pattern at over 10 days out. **but I'm really hoping it's wrong or at least the timing is wrong.  

 

I hope this is not the one time that it is exactly right 10 days out. I really don't want rain on Halloween, at least not between 6 and 8 pm.

[POWERSTROKE]

Thanks for sharing... I can see that is a pet peave for you. Though it does make alot more sense to forecast off of other factors instead of thickness alone. Even if you have a cold column there is always something to hender the drop or allow for colder temps. Espeically perfect conditions for raditional cooling.

Yeah even here 50 maybe a struggle. Needless to say it will be enjoyable Friday cold and blustery.

I love watching them bust. watch how temps change daily when they give their 5-7 day forecast.