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Weekend Storm Discussion Part II, 2/18-2/19


stormtracker

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yep, they don't have the 7PM info like the 0Z models for those who may not have known that fact

I never knew that Mitch thanks for the info, now i have to stay up until 3 a.m. so i can analyze a SREF run that is 2.5 days out from the storm. I think SREF stands for SHORT range ensemble forecast :axe: .

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Think there's a few vorts on the NAM? lol - It's probably going to come a bit further north/quicker on this run - NAM is further west with the northern stream vort and more NE with the southern stream closed low

yeah, check out what's going on in Nebraska at 33 hrs

looks to drop into the trough

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This dude Hurley over at HPC wrote a fantastic essay about the impending system.

I highlighted the more exciting concepts. In a nutshell, he isn't certain what will happen

but he knows it will be really interesting. :pimp:

Hurley must be a snow weenie. :snowman:

.SRN OH VLY/NRN TN VLY/APPALACHIANS/MID-ATL...

SRN STREAM SHORT WAVE CURRENTLY OVER BAJA CA WILL MOVE ACROSS TX

ENE INTO THE LOWER MID ATLC REGION OVER THE WEEKEND. SUBTLE

DIFFERENCES REMAIN WITH THE OPERATIONAL MODELS AS THIS SYSTEM

APPROACHES THE ERN SEABOARD. HPC GENERALLY FAVORED A

GFS-ECMWF-UKMET BLEND IN TERMS OF THE MASS FIELDS AND LARGE-SCALE

FEATURES...AS THESE MODELS CLUSTERED RATHER WELL COMPARED TO THE

NAM (SLOWER) AND CMC (MUCH SLOWER). IN ADDITION...ALSO A CONCERN

WITH REGARD TO THE NAM WAS THE BROAD EXTENT OF SNOWFALL ACROSS THE

TN AND PTNS OF THE LOWER MS VLY...RESULTING FROM THE SLOWER/DEEPER

SOLN EARLIER COMPARED TO THE OTHER MODELS WITH A BROADER

CCB/BAROCLINIC LEAF/TROWAL STRUCTURE. AGAIN...WHAT IS RATHER CLEAR

WITH THIS SYSTEM IS THE ABUNDANCE OF AVAILABLE AND ANOMALOUS

MOISTURE CONTENT. 12Z GFS 850 MB MOISTURE FLUX ANOMALIES ARE AGAIN

PROGGED AT LEAST 5 TIMES ABOVE AVG INTO THE SERN STATES ON DAY 3.

THIS MOISTURE WILL SPREAD NORTHWARD FROM THE GULF OF MEXICO INTO

THE SOUTH AND SOUTHEAST AND EVENTUALLY LATER SAT INTO SUN MORNING

UP THE APPALACHIANS INTO THE MID-ATL REGION. MEANWHILE ALONG THE

NRN STREAM...A WEAKER SHORT WAVE AND ASSOCIATED FRONTAL ZONE WILL

SWEEP THROUGH THE NORTHEAST AND THE FRONTAL BOUNDARY WILL DIG

SEWRD INTO THE MID-ATL STATES. THE ASSCD STRENGTHENING UPPER LEVEL

CONFLUENCE ACROSS THE NE WILL SUPPLY LLVL COLD/DRY ADVECTION INTO

THE MID ATLC REGION (INCREASED NRLY ISALOBARIC FLOW VIA THE RIGHT

ENTRANCE REGION OF THE NRN JET). MEANWHILE...THE APPROACHING LEFT

EXIT REGION OF THE SRN STREAM JET STREAK WILL STRENGTHENING THE

S-N AGEOS FLOW AND MSTR/THETA-E ADVECTION ALOFT.

HOWEVER...POTENTIALLY COMPLICATING MATTERS WILL BE THE DEPTH OF

THE LLVL DRY AIR. THE LATEST (12Z) ECMWF AND (18Z) NAM SHOW A

SHARPENING S-N MOISTURE GRADIENT...WITH THESE MODELS NOW

ADVERTISING A FLATTER SYSTEM WITH MUCH LESS QPF INTO NRN VA/MD/SRN

PA. AS IS TYPICAL WITH THESE MILLER B TYPE SYSTEMS SOME 2-3 DAYS

OUT...MULTIPLE COMPETING FACTORS WILL LEAD TO A LOW CONFIDENCE

FCST IN TERMS OF SNOWFALL POTENTIAL. FIRST IS THE AFOREMENTIONED

MSTR DEPTH JUXTAPOSITIONED WITH THE SUFFICIENTLY COLD AIR...AS THE

LATEST NAM/ECMWF SHOW A NARROWING STRIP OF MOD/HEAVY SNOW.

MEANWHILE...CONVECTION IN THE GULF WILL ALSO BECOME A

FACTOR...THAT OF WHICH IS STILL UNKNOWN AT THIS POINT IN TERMS OF

STRENGTH AND SPEED OF THE SYSTEM (TIMING OF AMPLIFICATION/PHASING

PROCESS AND DEVELOPMENT/EXPANSION/ORIENTATION OF TROWAL AND CCB

LEAF). THE MID LEVEL DRY SLOT IS ALSO A CONCERN IN TERMS OF TOTAL

QPF...THOUGH MAY ALSO ENHANCE THE POTENTIAL ELEVATED INSTBY

FARTHER N. FOR NOW...HAVE INCLUDED A BROAD AREA OF MOD PROBS FOR

AT LEAST 4 INCHES ACROSS NRN/NW VA...SRN WV...AND ERN KY.

THE PROBABILITY OF SIGNIFICANT ICING IS LESS THAN 10 PERCENT.

HURLEY

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Given this is the NAM, who wants to bet it spits out 1"+ QPF for DC? Looks very juicy/better organized compared to 18z in addition to being further north.

My concern is the ridge is moving east faster on this run. So the kicker may kick it east a little faster, and the earlier phasing may be irrelevant.

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