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Jan 11-12 Model/Forecasting Discussion


Ji

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from the old thread:

Is it just me, or does it seem odd that the models show the 500mb wave coming out of the Pacific Northwest not having any real connection to the Gulf-Coast runner... and the models show the energy rolling zonally across the central Plains and into the Mid-Atlantic... but instead of a sfc low in the Ohio Valley and then perhaps a second coastal low forming near Chesapeake Bay, they keep bringing the sfc low that tracks along the Gulf Coast and draw it in north like a magnet?

good inquiry.. bringing forward here so maybe it can be addressed. to me it seems it wants to try to get a surface reflection going but maybe the fact that it cant amplify is the issue. it does definitely try to tug on the se u.s. slp to bring it north eventually

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AREA FORECAST DISCUSSION

NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC

217 PM EST SAT JAN 8 2011

.LONG TERM /SUNDAY NIGHT THROUGH SATURDAY/...

-- Changed Discussion --HIPRES RMNS OVHD SUN NGT/MON...ITS ARCTIC ORIGINS HELPG KEEP TEMPS

BELOW NRML. LOWS AGAIN IN TEENS SUN NGT MANY AREAS...THO A BIT

LIGHTER WINDS SHUD KEEP WIND CHILLS FROM DIPPING BELOW ZERO EVEN IN

NW CWA. WITH H8 TEMPS BELOW -5C MON...MAXIMA STRUGGLE TO RISE ABOUT

FRZG THRU THE RGN. CLR SKIES WILL GRADUALLY BCM OVC MON AFTN/EVE AS

LOPRES ACRS DEEP SOUTH BRINGS MID/HIGH LVL MOISTURE TO MID-ATLC.

SYNOPTIC PATTERN AND EVOLUTION OF A PAIR OF STORM SYSTEMS QUITE

COMPLICATED FOR MON NGT INTO WED. STRONG SHRTWV TROF BENEATH

SUBTROPICAL JET WILL INDUCE CYCLOGENESIS SUN ACRS TX...WITH LOPRES

RIDING ALONG NRN GULF COAST SUN NGT/MON. THIS SFC LOW SHUD CROSS

INTO ATLC OFF GA/FL COAST ON MON AS IT WEAKENS DUE TO LIFTING OF

SHRTWV TROF NWD TWD POLAR JET. AT SAME TIME...POTENT VORTICITY MAX

IN POLAR JET CROSSES CNTRL PLAINS AND INTO OH VLY. SFC CYCLONE ALONG

SE US COAST WILL NOT BE ABLE TO STRENGTHEN UNTIL THIS NRN JET ENERGY

CAN DRAW CLOSER TO IT...THUS THE LOCATION OF THESE TWO SYSTEMS WILL

BE CRITICAL IN HOW MUCH SNOW FALL ACRS MID-ATLC...AND MODELS NOT IN

GOOD AGREEMENT ATTM.

CURRENT FORECAST IS REFLECTIVE OF AFOREMENTIONED NRN BRANCH ENERGY

AND SRN COASTAL LOW NOT GETTING TO COMPLETELY PHASE UNTIL PASSING

N/E OF MID-ATLC. THIS SOLUTION WILL STILL PROVIDE LIKELY SN ACRS THE

RGN BEGINNING MONDAY NGT...AS ENHANCED VERTICAL MOTION/ISENTROPIC

LIFT SPREAD NWD FOR THE SW IN ASSOCIATION OF FLATTENING SRN JET

SHRTWV TROF. BEST CHC OF SN APPEARS TO BE TUE...AS EVEN WITHOUT

COASTAL LOPRES STRENGTHENING SIGNIFICANTLY...IT SHOULD BE CLOSE ENUF

TO BRING SOME PRECIP INTO RGN...AS WILL THE NRN DISTURBANCE AS IT

CROSSES NEAR NEAR AREA TUE. GUIDANCE SUGGESTS POTENTIAL FOR

SECONDARY AREA OF SFC LOPRES DVLPG OVR CNTRL APLCNS BEFORE MOVING N

OF RGN...WITH ITS OWN AREA OF ENHANCED QPF. THUS LIKELY POPS ARE

DEPICTED AREAWIDE. ALSO WORTH A MENTION IS POSSIBILITY THAT ENUF

WARM AIR WILL BE DRAWN N/E FROM ATLC THAT SOME PRECIP MAY BCM MIXED

WITH RN ACRS LWR SRN MD. ALL-IN-ALL...CONFIDENCE IN ACCUMULATING

SNOW DURG THIS PERIOD CONTINUES TO INCREASE...THO CONFIDENCE IN

SIGNIFICANT SNOW AMOUNTS REMAINS LOW.

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Looks like next weekend's event will probaby come in two pieces. A front and then a southern storm along it. Hopefully the front goes through first a decent period of time in advance.

Can we please stop posting stuff about the next weekend possible event, this is for the "Tuesday Snow Threat"

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from the old thread:

good inquiry.. bringing forward here so maybe it can be addressed. to me it seems it wants to try to get a surface reflection going but maybe the fact that it cant amplify is the issue. it does definitely try to tug on the se u.s. slp to bring it north eventually

Take a look at the 300 mb chart; really powerful jet streak but its axis doesn't "back".

In other words, it retains that W - E orientation. I would think that for a storm to pop,

you would need some vorticity and change of orientation at 300.

Also, we do get a weak low at 850 in our area, but without the return

flow out of the east as Wes has suggested in the past. So no entrainment

of Atlantic moisture.

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Can we please stop posting stuff about the next weekend possible event, this is for the "Tuesday Snow Threat"

Yeah now that it's just a thread for the Tuesday threat we should stop with the future stuff. However, before (to be fair) the thread did say "Jan 11-31" devilsmiley.gif

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From Ian in the other thread:

"more often than not we get less snow than expected i think.. save last yr i guess. i mean shoot there are some people north of here who might have expected like an additional 14" of snow this yr based on WSW and WWA alone. :P "

But on a positive note, of the 3 times I've had forecasted snow this year, 2 have overperformed. Maybe the next one will as well.

Question for someone: When models aren't showing what we want, many go to the "won't be sampled properly until" fallback position. But this time, we seem pretty confident of something, just don't know what. My question, when will the players all be on the field? I was reading somewhere here that the southern piece is still in NW Mexico, which the poster said was a very poor data area, and the northern piece was in western Canada, which they said wasn't sampled very well either. So, when, and, would we be shocked at some wild change at the time the data was better sampled? Maybe much better? :P

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Around here 3-6" is a significant storm :lmao:

Especially this year.

Semantics.

I'd refer to a 3-6" event as a snowfall, especially if it comes without wind and/or real cold. The latter would be a "storm" in my eyes.

And, for me, it doesn't matter what climo dictates - relativity has nothing to do with it.

And before anyone decides to jump on my back, I'm not complaining. Just stating my take on it.

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From Ian in the other thread:

"more often than not we get less snow than expected i think.. save last yr i guess. i mean shoot there are some people north of here who might have expected like an additional 14" of snow this yr based on WSW and WWA alone. :P "

But on a positive note, of the 3 times I've had forecasted snow this year, 2 have overperformed. Maybe the next one will as well.

Question for someone: When models aren't showing what we want, many go to the "won't be sampled properly until" fallback position. But this time, we seem pretty confident of something, just don't know what. My question, when will the players all be on the field? I was reading somewhere here that the southern piece is still in NW Mexico, which the poster said was a very poor data area, and the northern piece was in western Canada, which they said wasn't sampled very well either. So, when, and, would we be shocked at some wild change at the time the data was better sampled? Maybe much better? :P

They may be sampled relatively well now though there are always uncertainties about vortices over the northeast and little spokes swing around them. Even if the models had identical initial analysis and data assimulation methods. there still could be signficant differences at times depending on how the various models handle various parameterization schemes for the boundary layer, convection, cloud physics and radiation and probably a couple more that I left out.

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but don;t worry, our friends in NE get clobbered by the SREF as it transfer energy to the Low offshore once to our north

look, I'm just posting this; I'm not saying its right

for BWI, SREF has stunk in every event this year but 12/16 it did OK

sref_bsp_087s.gif

It is the NAM scenario taken to the extreme. Just another camp to look at. We are in the Euro money range so ride it until it throws you.

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OTS.

This storm really goes both to our NW and to our SE. State College PA will get 10"(Yes I was there for 5 years and I'm going against models.) " NYC will get 10" NrN Georgia may get 10". We will get 4-6" and the dryslot.

850MB and 700MB close off too far noprth for us, this is a classic too DC dryslot Miller B. Hopefully iut won't be as bad as 2005

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