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NYC/PHL Dec 26-27 Potential - Part 5


am19psu

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MODEL DIAGNOSTIC DISCUSSION

NWS HYDROMETEOROLOGICAL PREDICTION CENTER CAMP SPRINGS MD

1016 AM EST FRI DEC 24 2010

VALID DEC 24/1200 UTC THRU DEC 28/0000 UTC

...SEE NOUS42 KWNO ADMNFD FOR THE STATUS OF THE UPPER AIR

INGEST...

12Z NAM EVALUATION

INITIALIZATION ERRORS DO NOT APPEAR TO SIGNIFICANTLY IMPACT ITS

SOLUTION.

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Either the GFS scores a huge coup here or all the other models are right...I'd favor the other models right now but they, too, are slowly shifting west. That makes me think they may come around at 0z, or at least much closer. All assuming this GFS run isn't a blip, of course.

If this thing crawls up the coast (very premature but hypothetically) just inside of the 12z GFS depiction, who won over all, the Euro or the GFS?

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We'd have to learn more as to what those were exactly, it could be major or it could be nothing...the fact the GEM though trended clearly amplified at 500 makes me believe there is something to whats going on more than errors.

I concur. That problem exits more often then not every model run and HPC is good about putting info out on that.

Somtimes it impacts resuts, other times it does not.

ERIC

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We'd have to learn more as to what those were exactly, it could be major or it could be nothing...the fact the GEM though trended clearly amplified at 500 makes me believe there is something to whats going on more than errors.

Yeah...I strongly agree. The NAM has been trending stronger w/ the feature through the plains for four runs now and is miles away from showing a huge hit.

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The reason the GGEM is not a hit like the GFS is its handling of the southern s/w....all models have trended stronger/sharper/faster with the northern s/w which is great but the GGEM/NAM drive part of the s/w into the GOM...while the GFS shows the northern stream being able to tug and capture cleanly the southern s/w

The best thing to do is watch the w/v loop and see which model is handling the southern s/w correctly.

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From NWS Taunton:

HIGHLIGHTS

* POTENTIAL WINTER STORM SUNDAY THROUGH MONDAY.

SPECIAL NOTE AT 1140 AM...WE HAVE GOTTEN A GOOD LOOK AT THE 12Z NAM

AS WELL AS A QUICK LOOK AT THE 12Z GFS THROUGH TUESDAY /SO FAR/. WE

HAVE SEEN THE DRAMATIC TREND THAT THE GFS HAS TAKEN ON THIS RUN...AS

WELL AS THE W TREND ON THE NAM /THOUGH REMAINING WELL S OF THE

BENCHMARK/. WE WANTED TO NOTE THAT WE HAVE RECEIVED MESSAGES FROM

HPC ABOUT INITIALIZATION PROBLEMS ON BOTH THE NAM AND GFS RUNS THIS

MORNING. HAVING WORKED ON THIS DESK FOR THE LAST SEVERAL DAYS...ONE

THING THAT HAS SHOWN THROUGH IS THE LACK OF RUN-TO-RUN CONSISTENCY

BETWEEN INDIVIDUAL MODELS. WHILE WE ARE NOT RULING OUT A SHIFT TO

THE W...WE DO NOT WANT TO JUMP ON THE BANDWAGON EITHER. WANT TO

WAIT UNTIL WE GET A LOOK AT THE ECMWF RUN BEFORE MAKING ANY MAJOR

CHANGES.

http://forecast.weather.gov/product.php?site=NWS&issuedby=BOX&product=AFD&format=CI&version=1&glossary=1&highlight=off

ECMWF will be big...

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I wonder how the ensemble mean calculation incorporates the operation run - and if it changes the relative weighting in the short term (for example giving more weight to the OP run).

Haven't seen the individual members, but the ensemble looks an awful lot like the OP, which is strange considering how the last few ensemble cycles have looked in terms of spread and mean.

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I stopped posting just to see what would happen, and every time I look back at the models, a little more west. This GFS run was just nuts, a quick phase and up the coast, and with full ensemble support, then it should be a legit in its own regards.

Do the initialization errors have any impact?

Not that they have noted. The NAM was not affected, and the GFS discussion is not out yet. Regardless of the errors, it would not fully account for the 150 mile difference, as snowgoose pointed out. I would assume unless the northern vortex was mismodeled, then it might be other factors.

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When you read between the lines, they also mention the 00z Euro was off as well, and they are just following continuity. Man, the plot keeps getting thicker.

INITIALIZATION ERRORS IN NUMEROUS DIAGNOSTIC

QUANTITIES...INCLUDING HEIGHT/VORTICITY FIELDS/RH...ARE EVIDENT IN

BOTH THE 12Z NAM/GFS WITH SMALL BUT LIKELY SIGNIFICANT SHORTWAVE

TROUGHS OVER SOUTH DAKOTA/NEBRASKA ALONG WITH

SASKATCHEWAN/MANITOBA...WITH THESE AREAS ALSO NOT PARTICULARLY

RESOLVED OR PREDICTED WELL BY THE 00Z ECMWF. THUS...THE SPECIFIC

PREDICTIONS BY ALL DETERMINISTIC GUIDANCE ARE IN QUESTION...WITH

THE RECOMMENDATION TO FOLLOW CONTINUITY...WITH THE FINAL OUTCOME

MOST BELIEVED TO LIE BETWEEN THE 06Z GFS AND 00Z ECMWF.

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A bit too early for the SUNY MM5?

In my opinion that Suny MM5 model is the best kept secret around when it comes to short term forecasting and especially for temperature profile and precipitation type forecasting.

Also if the 12Z GFS verifies The Weather Channel will need to change that goofy storm track graphic they have up of the eastern seaboard

they cease to amaze me.

I mentioned to my clients that forecasting this storm has equaled to being in a boxing match this week. Good thing there ready to go no matter what happens.

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HPC disregards the 12z GFS speaking about significant initialization errors on both the NAM and GFS.

That being said, using simuawips analysis...I don't see many differences if any at all in regards to the shortwave over the Northern Plains.

Aren't the ensembles run on slightly different initialization conditions to see the results of those changes? If so why do those also show a big hit then?

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im kinda laughing rite now because you look at ensembles and it fully supports the op and i find it hard to believe that there wrong also i think hpc is covering there arse by throwing models out til the euro comes out if you ask me

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The 12z GFS if verified would mean a 3 to 6" snow for the NW Philly burbs taken verbatim with 0.35" of liquid....closer to 5 on the upper end

actually if the 12gfs verified, it shows 4-8 in leheigh valley and 7-11 in phill, so about 7-9 or so in philly burbs.

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