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Dec 5-6 Round Two? NAM brings "sling-shot" Upper Low into SW and the fun has just begun!


wxhstn74

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MODEL DIAGNOSTIC DISCUSSION

NWS HYDROMETEOROLOGICAL PREDICTION CENTER CAMP SPRINGS MD

1145 PM EST FRI DEC 02 2011

VALID DEC 03/0000 UTC THRU DEC 06/1200 UTC

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

INGEST...

00Z NAM/GFS EVALUATION AND PRELIMINARY PREFERENCES

MODEL INITIALIZATION ERRORS DO NOT APPEAR TO HAVE A SIGNIFICANT

IMPACT ON THE FORECAST.

...ENERGY REACHING THE SOUTHWEST BY MON...

...TROF REMAINING OVER THE PLAINS/NRN TIER MON ONWARD...

PREFERENCE: NAM/12Z ECMWF COMPROMISE

THE GFS SHOWS A FARTHER EWD TRACK OF THE WRN CONUS ENERGY VERSUS

THE NAM FROM SUN ONWARD. BY F84 EARLY TUE THE GFS TRENDS TOWARD A

LESS POSITIVELY TILTED PLAINS/NRN TIER TROF THAN THE NAM... AND

DISPLAYS MUCH GREATER PHASING BETWEEN NRN TIER AND SWRN ENERGY IN

CONTRAST TO THE NAM THAT MAINTAINS A CLOSED MID LVL CENTER OVER

THE AZ/NM BORDER. OTHER MODEL/ENSEMBLE GUIDANCE DEVELOPS AT LEAST

A MEDIUM AMOUNT OF SPREAD BY LATE IN THE PERIOD. THE MOST COMMON

THEME IS TOWARD SLOWER PROGRESSION OF THE WRN CONUS ENERGY THAN

THE GFS... AND GREATER POSITIVE TILT OF PLAINS/NRN TIER ENERGY

THAN THE GFS. THE 21Z SREF MEAN BECOMES THE WWD/SLOW EXTREME WITH

THE SWRN CONUS ENERGY WHILE THE 18Z GEFS MEAN IS ALSO RELATIVELY

SLOW BUT NOT AS DEEP/WWD AS THE SREF MEAN. RECENT HISTORY OF

GUIDANCE IN THIS MEAN PATTERN HAS NOT FAVORED ERN SOLNS EITHER...

AND THE GFS FLATTENS THE UPSTREAM RIDGE MORE THAN CONSENSUS BY

MON... SO WILL CONSIDER THE GFS AS THE LEAST LIKELY SCENARIO.

HOWEVER WITH THE ECMWF HAVING BEEN ONE OF THE MORE STABLE/RELIABLE

PIECES OF GUIDANCE IN THIS PATTERN... AND OFFERING A SOLN THAT

ACTUALLY TRENDS A LITTLE FASTER THAN THE NAM... WOULD NOT WANT TO

GO ANY FARTHER WWD THAN A NAM/12Z ECMWF COMPROMISE AT THIS TIME.

MEANWHILE BY F84 EARLY TUE THE NAM TRENDS A BIT TOWARD THE DEEP

SIDE OF THE NON-GFS SPREAD WITH THE PLAINS/NRN TIER TROF. THESE

CONSIDERATIONS FAVOR A NAM/12Z ECMWF COMPROMISE AS THE BEST

STARTING POINT FOR THE FCST AT THIS TIME. CONFIDENCE IS SLIGHTLY

BELOW AVERAGE.

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This event has me very interested, as these waves that ride up tight baroclinic zones normally yield very nicely. Also with the gulf being open for business with the return flow around the high along the East Coast, you know this is going to be a moisture ladened system. I wouldn't be at all surprised to see QPF amounts go up as we move forward toward this event. Also as someone noted earlier in the thread that high moving Southeast from Canada will allow for a nice gradient between the system and the high pressure allowing for some wind to be thrown into the mix.

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