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December 27/28 Storm Part II


Typhoon Tip

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".LONG TERM /WEDNESDAY NIGHT THROUGH TUESDAY/...

COMPLEX STORM SYSTEM MOVING OUT OF THE GULF STATE THIS AFTERNOON.

THIS SYSTEM WILL REFORM OFF THE MID ATLANTIC COAST WED...BEFORE

MOVING NE. GFS...AND THE EURO ARE IN AGREEING CAMPS IN TERMS OF

TRACK AND COOLER THERMAL PROFILE. THE NAM IS VERY WARM...WITH THE

GGEM VERY COLD. HAVE FOLLOWED THE THE GFS/EURO SOLUTION. HAVING SAID

THAT...TREMENDOUS AMOUNTS OF CONVECTION OVER THE GULF STATES MAY

PLAY HAVOC WITH THE TRACK OF THIS LOW...AND WITH OUR

CURRENT...NEWLY FORMED SNOWPACK IN PLACE...HAVE NOT TOTALLY

DISCOUNTED THE POSSIBLY OF THE COOLER GGEM SOLUTION.

THEREFORE...HAVE LEFT WINTER STORM WATCHES UP ALONG THE COAST

THROUGH THURSDAY NIGHT IN THE EVENT THIS COOLER SCENARIO COMES TO

FRUITION. IN ANY CASE...THERE WILL BE A SHARP GRADIENT ALONG THE

COAST TO INTERIOR AREAS.

IN THE MEANTIME...WINTER STORM WARNINGS HAVE BEEN HOISTED FOR THE

INTERIOR. MANY AREAS WILL HAVE CLOSE TO A FOOT OF SNOW...WITH MORE

POSSIBLY ACROSS THE HIGHER FACING NE TERRAIN...AND LESS POSSIBLE

OVER THE LOW LYING VALLEYS (PARTICULARLY THE CT RIVER VALLEY)."

GYX AFD for Storm... great point to leave Winter Storm Watches up along the Maine Coastline... may still take a slightly colder track.

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Gun to my head, I will take the GFS for here. The Nam has been horrid lately with low-level temperatures and this may be affecting it's snow output.

According to the HPC diagnostics discussion the 0z NAM has initialization errors:

INITIALLY, THE 00Z NAM APPEARS TO BE 2-3C TOO WARM WITH ITS 850

HPA FREEZING LINE ACROSS VIRGINIA/MARYLAND AND THE UPPER OHIO

VALLEY, WHICH HAS POSSIBLE IMPLICATIONS FOR ITS FORECAST WINTER

WEATHER PRECIPITATION TYPES EARLY ON.

DURING THE SHORT RANGE PERIOD, THE 00Z NAM BECOMES A SLOWER THAN

THE REMAINDER OF THE GUIDANCE WITH THE SYSTEM MOVING THROUGH THE

NORTHEAST FROM LATE THURSDAY ONWARD, AND LIES NEAR THE SOUTHWEST

CORNER OF THE 12Z GLOBAL ENSEMBLE SPREAD WITH ITS ASSOCIATED

SURFACE LOW POSITION FRIDAY MORNING.

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Well to be fair, BOX has like 8" for ORH I think...the big 10-14" is just NW of that area...and east of Westborough/Framingham they have 2-4". They just have an insane gradient.

They have 10-14" going right down the ridge line there to ORH airport/Paxton/Leicester in their map.

But even for Weenie ridge in Princeton...I'm a bit skeptical of 10-14"...I guess I could see 10"...14" might be tough.

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According to the HPC diagnostics discussion the 0z NAM has initialization errors:

INITIALLY, THE 00Z NAM APPEARS TO BE 2-3C TOO WARM WITH ITS 850

HPA FREEZING LINE ACROSS VIRGINIA/MARYLAND AND THE UPPER OHIO

VALLEY, WHICH HAS POSSIBLE IMPLICATIONS FOR ITS FORECAST WINTER

WEATHER PRECIPITATION TYPES EARLY ON.

DURING THE SHORT RANGE PERIOD, THE 00Z NAM BECOMES A SLOWER THAN

THE REMAINDER OF THE GUIDANCE WITH THE SYSTEM MOVING THROUGH THE

NORTHEAST FROM LATE THURSDAY ONWARD, AND LIES NEAR THE SOUTHWEST

CORNER OF THE 12Z GLOBAL ENSEMBLE SPREAD WITH ITS ASSOCIATED

SURFACE LOW POSITION FRIDAY MORNING.

They really need to look at what they're doing with the NAM. It's not really even usable most of the time...and this year that's made it all the way inside of even 12 hours. The model has gotten worse not better in the last 1-2 years.

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NCEP just updated. GFS has the same temp issues but in a different area (too warm).

STORM MOVING ACROSS THE SOUTH AND EAST

======================================

PREFERENCE: NON-NAM COMPROMISE WITH AVERAGE CONFIDENCE

INITIALLY, THE 00Z NAM APPEARS TO BE 2-3C TOO WARM WITH ITS 850

HPA FREEZING LINE ACROSS VIRGINIA/MARYLAND AND THE UPPER OHIO

VALLEY. THE 00Z GFS PROBLEMS ARE CONSTRAINED TO A 2-3C ERROR IN

THE UPPER OHIO VALLEY. THESE 850 HPA TEMPERATURE ERRORS HAVE

POSSIBLE IMPLICATIONS FOR THEIR FORECAST WINTER WEATHER

PRECIPITATION TYPES EARLY ON. SEE WINTER WEATHER

GRAPHICS/PRODUCTS FROM HPC AND LOCAL FORECAST OFFICES FOR MORE ON

SNOW/SLEET/FREEZING RAIN EXPECTATIONS WITH THIS CYCLONE.

DURING THE SHORT RANGE PERIOD, THE 00Z NAM BECOMES A SLOWER THAN

THE REMAINDER OF THE GUIDANCE WITH THE SYSTEM MOVING THROUGH THE

NORTHEAST FROM LATE THURSDAY ONWARD, AND LIES NEAR THE SOUTHWEST

CORNER OF THE 12Z GLOBAL ENSEMBLE SPREAD WITH ITS ASSOCIATED

SURFACE LOW POSITION FRIDAY MORNING. TREND-WISE, THE GUIDANCE HAS

STRENGTHENED THIS SYSTEM OVER THEIR PAST DAY OF RUNS, BUT THE NAM

HAS STOPPED TRENDING QUICKER/NORTHEAST. WITH THE 21Z SREF/18Z

GEFS/12Z ECMWF ENSEMBLE MEANS SUPPORTING THE QUICKER NON-NAM

CONSENSUS, THE PREFERENCE IS FOR A NON-NAM COMPROMISE HERE WITH

AVERAGE CONFIDENCE CONSIDERING ITS PROGRESSIVE NATURE.

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Tough forecast for all of SNE tonight. This is one of those events that could go either way. WAA could win out a la the NAM and flip many areas to sleet and rain faster or the CAD and dynamic cooling could offset the WAA for a good chunk of the event and lead to significant totals for the interior. I don't think coastal sections look too good either way. My numbers reflect what I believe to be a middle ground scenario. This could go up or down depending on how this thing transpires.

I'd say < 1" for BOS (east wind of death without strong cold airmass), 4-6" for ORH, 2-4" for BDL, and 1-3" PVD.

Near my BY, I'm going with 7-9" for PSF with amounts of 10-12" for the east slope above 1K and north of the Pike. North of ORH around Wachusett is probably 7-9". Much of NNE does well with a lot of 8-12"+ amounts where there is no taint..

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but does it make sense?

I don't see a reason to believe it over a skillful ensemble of the Euro/GFS/GEFS/Euro ensembles/UKMET/RGEM

I'm not sure why its so warm. We'll find out who is right and who is wrong. I think the smart money would probably be on the latter modle set.

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Here's tonights vs the 12z same time. The one with a bit more ML warming is the 0z tonight (look for pinks in CT for those with tired eyes)

post-3232-0-79839200-1356495069_thumb.pnpost-3232-0-28169500-1356495074_thumb.pn

RGEM still keeps HPN and Danbury snow for a good 6hrs. Can't say for sure there won't be a warm layer somewhere, but surface will be close to freezing during that time. The warmup should occur after that first band subsides for most of CT and MASS. I'm guessing mid 30s interior to low 40s along the shore.

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Tough forecast for all of SNE tonight. This is one of those events that could go either way. WAA could win out a la the NAM and flip many areas to sleet and rain faster or the CAD and dynamic cooling could offset the WAA for a good chunk of the event and lead to significant totals for the interior. I don't think coastal sections look too good either way. My numbers reflect what I believe to be a middle ground scenario. This could go up or down depending on how this thing transpires.

I'd say < 1" for BOS (east wind of death without strong cold airmass), 4-6" for ORH, 2-4" for BDL, and 1-3" PVD.

Near my BY, I'm going with 7-9" for PSF with amounts of 10-12" for the east slope above 1K and north of the Pike. North of ORH around Wachusett is probably 7-9". Much of NNE does well with a lot of 8-12"+ amounts where there is no taint..

I think people are getting too caught up in the east wind thing being a big deal here. I still don't understand how so many meteorologists can be so conservative for Boston, which is a snow town in SW Flow events generally. The GFS, which is MUCH warmer than the Euro or RGEM, still shows a solid frame of .25" QPF for Boston at 24 hours with the 850 line straddling the MA/CT border and the freezing line JUST north of Logan.

Dewpoints are in the teens right now even on the water. Don't see how you're going to change such a cold, dry airmass over that quickly especially knowing climo east of the Apps.

Finally, why are you still talking about the NAM when HPC has thrown it out for initialization errors?

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They have 10-14" going right down the ridge line there to ORH airport/Paxton/Leicester in their map.

But even for Weenie ridge in Princeton...I'm a bit skeptical of 10-14"...I guess I could see 10"...14" might be tough.

Oh okay...yeah the BOX map barely has my area in 8-10"...like a few miles from 6-8"...which is a few miles from 4-6"....and so on. Hell of a forecast here. As bad as it gets.

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I think people are getting too caught up in the east wind thing being a big deal here. I still don't understand how so many meteorologists can be so conservative for Boston, which is a snow town in SW Flow events generally. The GFS, which is MUCH warmer than the Euro or RGEM, still shows a solid frame of .25" QPF for Boston at 24 hours with the 850 line straddling the MA/CT border and the freezing line JUST north of Logan.

Dewpoints are in the teens right now even on the water. Don't see how you're going to change such a cold, dry airmass over that quickly especially knowing climo east of the Apps.

Finally, why are you still talking about the NAM when HPC has thrown it out for initialization errors?

BOS is in a tough spot when the winds go east. In many of the other SWFEs, the winds stayed more northerly for BOS. This is almost like a SWFE transitioning into a full blown coastal...the winds are much stronger and easterly than a typical weak sfc wave with ripping SW winds in the mid-levels...those things often had a light wind out of the NE/NNE.

GFS soundings did show a few hours of wet snow for Logan...it will be close. I'm sure just off the water like where Jerry is can rip for a litte bit...but Logan will torch quickly in December with an east wind.

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BOS is in a tough spot when the winds go east. In many of the other SWFEs, the winds stayed more northerly for BOS. This is almost like a SWFE transitioning into a full blown coastal...the winds are much stronger and easterly than a typical weak sfc wave with ripping SW winds in the mid-levels...those things often had a light wind out of the NE/NNE.

GFS soundings did show a few hours of wet snow for Logan...it will be close. I'm sure just off the water like where Jerry is can rip for a litte bit...but Logan will torch quickly in December with an east wind.

Well if Jerrys rippin and I'm raining it's gonna be a sad time

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