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2/19 East Coast Winter Storm Threat (Part 2)


OKpowdah

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Not sure if anyone from the 1st topic on this storm posted this, don't have the time to go through that. From the HPC after all the 12z models came in:

..SHORTWAVE TROUGH ENTERING THE PLAINS/MIDWEST FRI-SAT...

Sure you can blame the 12z run on bad initialization but are they calling that flag on the monster 0z hit from last night also?

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Sure you can blame the 12z run on bad initialization but are they calling that flag on the monster 0z hit from last night also?

Here is what they said concerning the 0z runs of last night, looks like no in-depth reason except they just went with the EURO:

..SHORTWAVE CROSSING THE UPPER MIDWEST DAY 3...

PREFERENCE: ECMWF

THE NAM IS MUCH FASTER AND MORE PROGRESSIVE THAN THE ECMWF WITH

THIS IMPULSE. THE GFS IS NORTH OF THE ECMWF WITH THE TRACK OF THE

WAVE. WILL RELY ON THE CONSISTENT ECMWF AT THIS POINT...AS

BROADLY SUPPORTED BY THE GEM GLOBAL AND UKMET.

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Not sure if anyone from the 1st topic on this storm posted this, don't have the time to go through that. From the HPC after all the 12z models came in:

..SHORTWAVE TROUGH ENTERING THE PLAINS/MIDWEST FRI-SAT...

PREFERENCE: ECMWF

THE GFS APPEARS TO HAVE WORSE INITIALIZATION OF THE TROUGH'S

PLACEMENT OVER BRITISH COLUMBIA AND NUNAVUT THIS MORNING COMPARED

TO THE NAM/ECMWF. MEANWHILE...THE GFS IS MOST AGGRESSIVE IN

ALLOWING AN UPSTREAM PERTURBATION CURRENTLY OVER THE PACIFIC TO

CUT THROUGH THE SHORTWAVE RIDGE OVER THE CANADIAN ROCKIES ON

THURSDAY...WHICH THEN PHASES WITH THE NORTHERN STREAM AND SLOWS

THE ENTIRE GFS SOLUTION. THE COMBINATION OF WORSE INITIALIZATION

AND QUESTIONABLE AND EVEN SUSPICIOUS PHASING OF THE SEPARATE

STREAMS IS SUFFICIENT TO DISCARD THE GFS PARTICULARLY LATE IN THE

PERIOD. AMONG THE REMAINING SOLUTIONS...THE NAM BECOMES SLIGHTLY

FASTER THAN THE CANADIAN/ECMWF...WHILE THE UKMET IS SLOW AND

AMPLIFIED...WITH ITS GREATER AMPLIFICATION POSSIBLY AN INDICATION

OF ITS STRONG BIAS AT LATER TIME FRAMES. THUS...THE UKMET IS

DISCOUNTED. MEANWHILE...THE NAM...WHILE PLAUSIBLE...IS CONSIDERED

LESS LIKELY THAN THE ECMWF DUE TO ITS NARROWER DATA ASSIMILATION

WINDOW AND ULTIMATELY QUESTIONABLE INITIALIZATION PARTICULARLY AT

THE HIGHER LATITUDES.

(http://www.hpc.ncep....php?disc=pmdhmd)

In my advanced forecasting class, my professor discussed this storm, one main issue with the 12z GFS was the longwave and how short and funky it was, he claims that the atmosphere is uncomfortable when you have a short/funky longwave. He also discussed the issues concerning the cut off low in the southwest and how bad the models do trying to predict the energy coming out of it. After over 30 years of experience, he is not sold on this storm. To him too many issues. To me, the GFS is trying to phase, when it is not phase until later. Not buying it, and until otherwise (aka, a high pressure is in Southern Canada - Ontario or Quebec), no big storm for us.

The issue here isn't what's coming out of the SW feature - it gets ejected en mass in all operational runs and the majority of their respective ensemble members. If that kind of uncertainty were in play, you'd have a variety of sheared solutions ...some leaving much behind. This strictly is related to the degree of phasing with the northern stream after the fact; the difference is either flatter wave that is pure southern stream that rolls out way S vs. get pulled N during phase. This latter concern is the uncertainty in the forecast, not so much the handling of the SW feature.

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lol are we all looking at the same NAM ??

At least Ginx and I are on the same page

I try not to look at the NAM outside of about 18-24 hours.

The GFS has the changes noted above, and it's also muting out the intermediate s/w between the main complex in the north and the southwest s/w. This was the one prominently featured on the big GFS storm runs, but lacking on the GGEM and Euro.

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I think the southern stream at 33 hours does looka bit faster than the 18z run, but the northern stream is also faster and so it may have a hard time phasing them like it did at 18z...not that it would be a surprise because that was the most northwest amped solution we've seen on operational guidance thus far...it would be natural to come back to the pack a bit. The question is potentially where the other guidance meets it.

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I think the southern stream at 33 hours does looka bit faster than the 18z run, but the northern stream is also faster and so it may have a hard time phasing them like it did at 18z...not that it would be a surprise because that was the most northwest amped solution we've seen on operational guidance thus far...it would be natural to come back to the pack a bit. The question is potentially where the other guidance meets it.

I don't see that there's any way it's similar to the 18z. Too out of phase even very early on. Heading the other direction from the extreme of earlier today.

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