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November 2012 Observations and Discussions


Snow_Miser

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18z GFS pretty much shows exactly what I expect next week. A low will develop near Cape Hatteras on Sunday and Monday, then head to about 150 miles off the coast of New Jersey and deepen, much like the last storm and Sandy. Of course it will not be anywhere near as intense, however, it may have an opportunity to throw quite a bit of moisture back our way. The only change I would make on the depiction by the 18z GFS would be to keep the high stationed more back over Quebec, as it has the low escaping east over the Northern Atlantic. This is the same mistake it make with the last storm, which made temperatures appear that they would be a lot warmer than they turned out being. Hence, the solution I strongly believe will be a very snowy pre-Thanksgiving for our area. I have been watching this for about 5 days now and the model is showing nearly exactly what I have been thinking. Refer back to my post yesterday morning before the 12z run of the Euro yesterday showed something similar. It actually manages to deepen this to 990mb at 240 hrs. when it is about 150 miles off the NJ Coast.

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For whatever reason, there are many times when the GEFS in the long range can actually school the Euro out 10 days and beyond. For some reason when it gets to 7 or 8 days out, the GFS loses to the Euro. Just an observation I've noted.

Actually I don't have the particular graph with me, but the errors are like that, at least with the GFS vs Euro, not sure about GEFS (but I doubt the GEFS would be worse in the long-range).

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We managed to sneak in another below average day here in Dobbs Ferry. We reached a high of 53.7F after a low of 38.9F. Average is 57/38 so the day goes down as a -1 departure in the books for this location in Southern Westchester. Amazing thing is that it felt warm despite still being below our expected temperature for this time of year. Even more amazing is that there was still solid snow cover at 4pm this afternoon on all north-facing areas, including lawns, when I went up to Mt. Kisco, which is about 20 miles north of here.

We should get back to below average temperatures later this week. NWS has 49/33 on Wednesday. Average by then is 55/37 for Dobbs Ferry, so we'd be -5 on the day if the forecast verified. I expect a string of days in the -4 to -6 departure range after the cold front goes by. With no torch on the horizon save the next couple days, I expect KNYC to finish November around -3 or so.

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There's definitely the signal of a storm brewing on the 0z GFS ENS at Hour 240:

post-475-0-56740900-1352613002_thumb.gif

This would almost certainly be rain, however, as the disturbance is entirely disconnected from the polar jet which is forced far north by the strong GoA low and accompanying +NAO.

The pattern does turn more interesting past Thanksgiving on the 0z GEFS, however, as the Aleutian ridge continues to build poleward and weaken the GoA low with a weak -NAO block:

post-475-0-02683900-1352613229_thumb.gif

post-475-0-49903600-1352613272_thumb.gif

There's definitely going to be a cold airmass over Alaska developing in the 2nd and 3rd week of November. It'll be fascinating to see if the Aleutian ridge starts to bring this southward as wavelengths continue to lengthen. I think the theory of a cold start to December holds legs, but we'll see..

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Bizarre pattern on the long range models. The northern stream is non existent so like zucker said there is no snow chance with this one. There's some cutoff lows and a tropical feed so who knows whats gonna happen

The wavelengths look kind of funny on the 00z Euro. It's almost like they're too short given how late in the fall it will be..

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The wavelengths look kind of funny on the 00z Euro. It's almost like they're too short given how late in the fall it will be..

0z ECM was definitely an improvement in the long-range as it first develops a weak +PNA signal which provides a tad bit more cold air for the pre-Thanksgiving storm. It's still marginal but there's a better chance for snow if we have higher heights in the west.

At the end of the 0z run, there's an Alaska block/-EPO building as the PNA retrogrades west and strengthens. Atlantic still looks putrid though so I'd expect a strong gradient over SE Canada/Northern New England with temperatures slightly above average for NYC and limited snow chances. There's definitely signs of ridging over the Aleutians and Alaska though in late November so that should still get the ball rolling. Average highs are still around 53F here on Day 10 of the Euro so I'm not too concerned....a good pattern is still likely to produce rain at that point.

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The operational run of the 6z GFS continues with the pre-Thanksgiving Nor'easter threat and a significant number of the 6z GFS ensemble members support this general idea. While the European model does not support the Nor'easter threat, HPC has concluded that it is likely incorrect and has sided with the GFS in the time period leading up to this event. I also watch the control run of the European model to determine if it is in agreement with the operational run, which it typically is, but it is not this morning. The control run looks very different than the operational run, also not agreeing on the Nor'easter, but much more potent with some energy coming out of the Mid-west and forming a Nor'easter in our area for next Wednesday into Thanksgiving morning. What is of interest to me is not the details of the control run, but the fact that it does not agree with the operational run of the Euro leading up to this event. This is telling me that HPC may be correct in that the GFS may be handling the situation better leading up to our potential pre-Thanksgiving Nor'easter. Of course, it is always dangerous to go against the Euro, but no model is particularly good at that range. I will continue going with the GFS until or unless it decides to give up on the idea. The control run of the Euro shows no signs of the warmup out to 360 hrs that many people have been talking about. Also, as far as temperatures looking too warm for snow with the pre-thanksgiving storm, remember they also looked too warm until only a day before the last storm on the GFS because it was completely mishandling the high pressure system to the north and I can only imagine the model is doing the same thing this time, so I would not pay much attention to the 850 temps, but pay a lot of attention to the fact that you will have a 1030+ high over Quebec and may have a low about 150 miles off the coast of New Jersey.

PRELIMINARY EXTENDED FORECAST DISCUSSION

NWS HYDROMETEOROLOGICAL PREDICTION CENTER COLLEGE PARK MD

848 AM EST SUN NOV 11 2012

VALID 12Z THU NOV 15 2012 - 12Z SUN NOV 18 2012

START OF THE PERIOD...14/12Z DEPICTS A H7 WAVE ALONG 100W LIFTING

NORTHEASTWARD WITH A WEAK SPLIT-FLOW WAVE DOWNSTREAM ACROSS DEEP

SOUTH AND NORTH OF THE ARCTIC FRONTAL BOUNDARY. THE OPERATIONAL

00Z ECMWF/CANADIAN ARE VERY BULLISH WITH THEIR QPFS ACROSS

GA/SC/OUTER BANKS...AND THE COASTAL WAVE SEEMS OUT OF PLACE WITH

THE MODIFIED ARCTIC FRONT ALREADY PUSHED THROUGH THE REGION...PER

OUR SFC GRAPHICS VALID 14/12Z. THAT SAID...

PROGRESSIVE LOW-AMPLITUDE FLOW PATTERN AND 'WAVE TRAIN' REALLY

STARTS AND ENDS WITH THE IMPULSES ORIGINATING ALONG THE WEST COAST

WHERE THEY'LL BE AMPLE MOISTURE TO WORK WITH.

INDICATION/TELECONNECTION OVER THE ARCTIC CIRCLE OF A SLOW

WESTWARD RETROGRESSION OF THE POLAR VORTEX IS INDICATED WITH THE

11/00Z ENSEMBLE GUIDANCE. WITH THIS SOLUTION 'DEAD SET' ON A DEEP

UPPER-LEVEL TROUGH ALONG THE WEST COAST OF NORTH AMERICA TO

GRADUALLY ANCHOR INVOF 135W-140W...WOULD ANTICIPATE OROGRAPHIC

PRECIPITATION IN THE WEST...GREAT BASIN AND CONTINENTAL DIVIDE.

THIS PREMISE MAY NOT BE A PERFECT PROG BY 180 HOURS...BUT THE

MEDIUM RANGE FORECAST CAN EASILY BLEND THE H7-H5 LAYER GEFS/ECMWF

MEANS THROUGH DAY 7 AND INCLUDE THE 'CUTOFF' SYSTEM MEANDERING

INVOF 35N 135W WITHIN THE MIX OF POTENTIAL LOW-AMPLITUDE WAVES

MIGRATING THROUGH THIS ZONAL FLOW PATTERN.

WHAT MUDDLES THE DAY-TO-DAY DETAILS IS THE BRIEF AND TEMPORARY

'WEAK BLOCK' ASPECT OF THE CUTOFF...WITH ALLOWANCE FOR SOUTHERN

STREAM FLOW TO UNDERCUT THIS EXPANSIVE UPPER-LEVEL TROUGH

CONFIGURATION DOWNSTREAM ALONG 30N-35N AS DEPICTED BY THE

ECMWF/GEFS ENSEMBLE MEANS THROUGH DAY 7. AGREE WITH THE MID SHIFT

WITH THE 00Z GFS AND GEFS/ECMWF MEANS DOWNSTREAM...HAVING A

GENERALLY BETTER 'FEEL' FOR THE BREAKDOWN AND PROGRESSION OF ANY

SUB-SYNOPTIC SYSTEM DEVELOPING IN THE SOUTHERN STREAM. BOTTOM LINE

HOWEVER...VERY LITTLE RETURN GULF FLOW TO WORK WITH AND UNABLE TO

FIND A SURFACE REFLECTION NEAR THE SOUTHEAST COAST AND/OR NORTHERN

GULF COAST IN THIS BRIEF SOUTHERN STREAM FLOW ALOFT.

DOWNSTREAM CONDITIONS EAST OF THE ROCKIES...DO NOT CHANGE

APPRECIABLY THROUGHOUT THE MEDIUM RANGE PERIOD AND CONTINUES TO BE

GENERALLY A 'DRY' AND 'COOL' FORECAST. WIDESPREAD HIGH PRESSURE AT

THE SURFACE SIGNALS DRY/STABLE AIR WITH LIMITED MOISTURE

AVAILABILITY AS THE PROGRESSION OF H7 WAVE ENERGY EJECTS ENEWD

FROM THE CENTRAL ROCKIES INTO THE UPPER GREAT LAKES. THE 00Z

OPERATIONAL ECMWF STILL APPEARS TO BE THE MODEL SOLUTION THAT IS

OUT OF STEP WITH ITS H5/H7 MEANS ALONG THE EAST AND WEST COASTS.

VOJTESAK

PREVIOUS DISCUSSION...

THE LONGWAVE FLOW IS EXPECTED TO REMAIN NEARLY ZONAL OVER THE

CONUS AND SOUTHERN CANADA FOR MOST OF THE UPCOMING MEDIUM RANGE

PERIOD...WITH A SIGNIFICANT UPPER TROUGH NEARING THE WEST COAST BY

DAY 7/SUN. THIS TROUGH IS THE RESULT OF MULTIPLE STREAM

INTERACTIONS OVER ALASKA...WITH ITS EARLY EVOLUTION FAVORING A

CONSIDERABLE SHORTWAVE RIDGE OVER THE GULF OF ALASKA AROUND DAY

3/WED...WHICH IN TURN PROMOTES DOWNSTREAM DIGGING OF ONE OR MORE

SHORTWAVE TROUGH ALONG THE WEST COAST. MODELS LATCH ONTO THIS

SOLUTION QUITE WELL WITH ONLY MINOR TIMING/STRENGTH DIFFERENCES

EARLY ON. HOWEVER...BY DAY 5/FRI THE 00Z GFS BECOMES FASTER THAN

THE 00Z ECMWF/CANADIAN WITH A MORE SIGNIFICANT TROUGH QUICKLY

FOLLOWING. GIVEN THE GROWING UNCERTAINTY AT THIS TIME FRAME...THE

PREFERENCE IS FOR THE MODEL CONSENSUS...WITH THE ENSEMBLE

SPAGHETTI DIAGRAMS FAVORING THE FASTER GFS. A SIMILAR APPROACH IS

PREFERRED OVER THE GREAT LAKES BY NEXT WEEKEND...WITH THE 00Z GFS

BETTER SUPPORTED BY OTHER GUIDANCE COMPARED TO THE 00Z

ECMWF...WHICH IS CONSIDERABLY STRONGER WITH HIGH PRESSURE BUILDING

INTO THE NORTHERN PLAINS/UPPER MIDWEST. THUS...

THE PRELIMINARY PRESSURES/FRONTS WILL USE A 50/50 BLEND OF THE

GFS/ECMWF TO BEGIN THE PERIOD...THEN GRADUALLY TRANSITION TOWARD A

50/50 BLEND OF THE GEFS MEAN/ECMWF ENSEMBLE MEAN BY DAYS

6/7...WITH MORE DETAILS FROM THE OPERATIONAL GFS PREFERRED OVER

THE OPERATIONAL ECMWF LATE IN THE PERIOD. JAMES

post-1914-0-92310700-1352634497_thumb.gi

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The last storm also looked like rain on the GFS until it happened. It shows an extended period of precipitation from Tuesday morning through Friday night as it merges two separate storms into one. This solution is insane and drops around 4 inches of precipitation through that time frame with the low in perfect position off the coast and a high in perfect position to the north. This solution is clearly nuts but is not outside the realm of possibilities at all.

The 12z GFS has the system sitting off of the coast for an extended period of time.

Pretty chilly rain for days if that were to verify.

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The last storm also looked like rain on the GFS until it happened. It shows an extended period of precipitation from Tuesday morning through Friday night as it merges two separate storms into one. This solution is insane and drops around 4 inches of precipitation through that time frame with the low in perfect position off the coast and a high in perfect position to the north. This solution is clearly nuts but is not outside the realm of possibilities at all.

The trends with the high to the north definitely need to be watched, IMO

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The trends with the high to the north definitely need to be watched, IMO

As weathergun alluded to, the strong high pressure is due to the confluent flow to the north and is not of arctic origin, and also undergoes significant modification. If you look at the 168 hour panel the arctic flow is almost completely cut off with most of the cold arctic confined to Alaska, near the pole, and on the other side of it and the best cold air source in relation to our area and that high pressure several hundred miles away if not more.

http://www.meteo.psu...RF_12z/f168.gif

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As weathergun alluded to, the strong high pressure is due to the confluent flow to the north and is not of arctic origin, and also undergoes significant modification. If you look at the 168 hour panel the arctic flow is almost completely cut off with most of the cold arctic confined to Alaska, near the pole, and on the other side of it and the best cold air source in relation to our area and that high pressure several hundred miles away if not more.

http://www.meteo.psu...RF_12z/f168.gif

Yes, the 12z GFS definitely would support a cold rain solution, but my statement pertained to trends with the high pressure that could possibly allow for more cold air to be present with this system, or even allow for a warmer system than is currently being modeled.

I could be wrong though with this assumption, please let me know if I am.

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Yes, the 12z GFS definitely would support a cold rain solution, but my statement pertained to trends with the high pressure that could possibly allow for more cold air to be present with this system, or even allow for a warmer system than is currently being modeled.

I could be wrong though with this assumption, please let me know if I am.

We need disturbance with polar or artic air, to phase with this storm. That's not looking very likely, with the polar jet running so far north.

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It certainly is a very positive sign as we enter into the winter months, this is something we did not see last year at this time. I think alot of the winter outlooks that are calling for stormy conditions will be on target, and this could potentially also bode well for above average snowfall this winter.

Another major nor'easter in the longer range panels. The GFS has TWO major Nor'Easters in the long range!

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