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Potential winter threats


tombo82685

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based on everyones analysis I thought that the strength of the s/w was less important than the PV breaking off and phasing in. If the s/w is strong and no phasing, no big storm. Maybe I'm missing something.

The position of the 500 vort is critical. The Euro last night had the 500 over NNE, the 12z had it over the Lakes. Both were about the same strength but the difference in location had big implications on the storm's genesis and track.

The s/w matters as well but if the 500 is over Maine you're getting a NW upper level flow over the NE and the storm misses wide right.

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GFS versus the ECM...

Be interesting to see if the GFS keeps this type of solution for 12 Z

Nah. The ECM had one run with the system OTS. Let's wait for model consistency before placing the models into camps. At this point, they ALL have the storm, which is what you want.

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I wouldn't be surprised if the 12z Euro shows what it did yesterday, and its not GFS vs. Euro just 1 run ago the Euro showed the same solution.

I am not saying that that is not a possibility but as it comes down to the latest data it would be the GFS versus the ECM.

GFS @ 00z had the storm and phased together at the right time...

GFS @ 06 Z had the storm and phased together again at the right time...

ECM did not phase & the result was well out at sea.

12 Z Ensemble means showed basically what tonights op ECM did and tonights 00z means supported the OP...though probably alot of spread....

Now, granted all models have the storm...GGEM looked like ECM and UKMET looked like it would be more on the GFS side...just as far as latest data is concerned...

So it will be very interesting to see if the GFS keeps on this track & phasing potential or if it goes the way of ECM & vice versa!

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Guest Patrick

LOL...

Keeping the potential threats in check in a pattern like this is tough... we are in somewhat uncharted waters in many ways.

It's December. There is massive blocking. There is a strong Nina, which may or may not be weakening as we speak. The models are resolving this ticking time bomb issue by showing a bomb somewhere. Nina says "Supress and squash." GFS says "massive blizzard."

The potential is huge, but it looks like some people got out of hand last night. We have about 4 more days to watch the models work this out...and then another 4 days to watch them work out the next S/W, and then another...

See HPC disco for some expert logic from this far out:

PRELIMINARY EXTENDED FORECAST DISCUSSION

NWS HYDROMETEOROLOGICAL PREDICTION CENTER CAMP SPRINGS MD

242 AM EST MON DEC 13 2010

VALID 12Z FRI DEC 17 2010 - 12Z MON DEC 20 2010

THE NEGATIVE PHASE OF THE NORTH ATLANTIC OSCILLATION IS FORECAST

TO SLOWLY WEAKEN DURING THE FORTHCOMING MEDIUM RANGE PERIOD...BUT

NOT BEFORE ADDING CONTINUED UNCERTAINTY TO BOTH THE LONGWAVE AND

SHORTWAVE PATTERNS AFFECTING NORTH AMERICA. THE DOMINANT LONGWAVE

ELEMENT CONTINUES TO BE A RETROGRADING UPPER HIGH FROM GREENLAND

INTO CANADA WHICH ACTS AS A HUGE BLOCK AGAINST SHORTWAVE TROUGHS

APPROACHING FROM THE PACIFIC. DETERMINISTIC AND ENSEMBLE GUIDANCE

SHOW INCREASING SPREAD RESOLVING THIS PATTERN WITH TIME...WITH

BOTH THE BLOCKING REGIME AND ITS POSITION AT THE MORE DATA-SPARSE

HIGHER LATITUDES SUGGESTING LOW PREDICTABILITY. THUS...THE

FORECAST PHILOSOPHY IS TO RELY UPON DETERMINISTIC GUIDANCE FOR

ONLY A SMALL PORTION OF THE MEDIUM RANGE FORECAST EARLY IN THE

PERIOD...BEFORE TRANSITIONING ENTIRELY TOWARD ENSEMBLE GUIDANCE TO

ADDRESS THE GROWING UNCERTAINTY.

REGARDING SYSTEM DETAILS...THE 00Z GFS CONTAINS THE LEAST AMOUNT

OF FORECAST CONFIDENCE AS EARLY AS DAY 3...WITH SHORTWAVE TROUGH

SOLUTIONS OVER THE UPPER MIDWEST AND NEAR THE CALIFORNIA COAST

WHICH LIE NEAR THE FAST AND STRONG EDGES OF THE SOLUTION ENVELOPE

RESPECTIVELY. THESE DIFFERENCES THEN GROW WITH TIME EVENTUALLY

CONTRIBUTING TO A SOLUTION WHICH FAVORS A MAJOR EAST COAST

SNOWSTORM BY DAYS 6/7. COMPARISONS WITH ALL OTHER DETERMINISTIC

AND ENSEMBLE GUIDANCE...WHICH COMPRISES OVER 100

SOLUTIONS...PLACES THE PROBABILITY OF SUCH AN EVENT AROUND 5

PERCENT. THUS...GIVEN A LACK OF CONFIDENCE IN THE MODEL'S SYSTEM

DETAILS EARLY IN THE PERIOD...ITS SOLUTION IS CURRENTLY DISCARDED.

OTHERWISE...THE 00Z ECMWF AND TO A LESSER EXTENT THE 00Z

CANADIAN/00Z UKMET/12Z JMA...PROJECT A MEAN DAY 3-7 PATTERN THAT

CONTAINS LONGER WAVELENGTH AND LESS AMPLITUDE FOR TROUGHS

EVENTUALLY EXITING THE NORTHEAST PACIFIC TROUGH. THIS

BROADER/FLATTER PATTERN...WHICH IS ALSO SUPPORT BY THE GLOBAL

ENSEMBLE MEANS...TELECONNECTS WELL WITH THE UNUSUALLY LARGE

POSITIVE MID-LEVEL HEIGHT ANOMALY FORMING OVER BAFFIN ISLAND IN

CANADA LATE IN THE PERIOD.

JAMES

Potential to not happen and needing a perfect scenario? Yep.

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HPC totally throwing out the GFS, likes the 0z Euro and its ensembles. This is looking pretty bleak right now from my perspective but we do have plenty of time.

Usually you're the voice of optimism I'm surprised at your lack of faith.

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