Prognostic Meteorological Discussion
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000
FXUS10 KWNH 061639
PMDHMD

MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1138 AM EST FRI MAR 06 2015

VALID MAR 06/1200 UTC THRU MAR 10/0000 UTC

...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR
INGEST...

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12Z NAM/GFS EVALUATION AND PRELIMINARY PREFERENCES
==================================================
NAM/GFS INITIALIZATION ERRORS DO NOT APPEAR TO
SIGNIFICANTLY AFFECT THEIR LARGE SCALE OUTPUT.
==================================================

...FRONTAL ZONE PUSHING THROUGH SOUTH FLORIDA FRIDAY NIGHT...

PREFERENCE: BLEND OF THE OPERATIONAL MODELS

SOME CONVECTIVE PRECIPITATION IS EXPECTED AS A FRONT SLIPS THROUGH
SOUTH FLORIDA FRIDAY EVENING AND POST-FRONTAL EASTERLY ONSHORE
FLOW STRENGTHENS SATURDAY. MODELS ARE HANDLING THE SCENARIO
SIMILARLY...INCLUDING IN THEIR PRECIPITATION OUTPUT. THE 00Z
ECMWF...HOWEVER...WAS ONE OF THE DRIER SOLUTIONS.


...BROAD TROUGH DEVELOPING IN THE CENTRAL AND SOUTHWEST U.S...

PREFERENCE: 00Z ECMWF...SUPPORTED BY THE ECMWF ENSEMBLE MEAN AND
OVERALL CONSENSUS

A CLOSED LOW OVER NORTHWEST MEXICO WILL MOVE EAST AND AWAY FROM A
BLOCKING RIDGE...ALLOWING THE LOW TO OPEN UP AS IT PHASES WITH
NORTHERN STREAM TROUGHING. THE ANTICIPATED RESULT WILL BE A
POSITIVELY TILTED TROUGH EXTENDING FROM THE MIDWEST STATES TO
SOUTHWEST TEXAS BY SUNDAY EVENING...WITH A SOUTHERN STREAM JET AND
ASSOCIATED GRADIENTS CONCENTRATED OVER TEXAS AND THE LOWER
MISSISSIPPI VALLEY.

THE MODELS SHOW MODERATELY GOOD AGREEMENT. THERE ARE NO STRONG
OUTLIERS...AND ONE COULD CHOOSE TO BLEND MANY OF THE OPERATIONAL
SOLUTIONS TOGETHER. WE PREFER...HOWEVER...TO POINT OUT THAT THE
00Z ECMWF APPEARS TO BE THE MOST REPRESENTATIVE OF CONSENSUS.
ECMWF MASS FIELDS AND PRECIPITATION OUTPUT CLOSELY MATCH THAT OF
THE ECMWF ENSEMBLE...BOTH OF WHICH REPRESENT A COMPROMISE BETWEEN
THE GFS...SUPPRESSED FARTHER SOUTH...AND THE NAM WITH ITS
PRECIPITATION FARTHER NORTH AND WEST. THE 00Z UKMET AND CANADIAN
WERE FAIRLY SIMILAR TO THE ECMWF...BUT THE UKMET APPEARED OVERLY
DEVELOPED WITH SURFACE LOW PRESSURE IN LOUISIANA BY 10/00Z. THE
CANADIAN WAS SLIGHTLY SLOW AND NOT AS DEEP AS THE CONSENSUS AT MID
LEVELS.


...WEST-NORTHWESTERLY FLOW OVER THE GREAT LAKES AND NEW ENGLAND...

PREFERENCE: BLEND OF 12Z NAM/GFS AND 00Z ECMWF...DROPPING THE NAM
ON DAY 3

BENEATH FAST WEST TO NORTHWESTERLY FLOW ALOFT...FRONTAL WAVES WILL
OCCUR ALONG THE INTERFACE BETWEEN ARCTIC AIR IN THE GREAT LAKES
AND NORTHEAST...AND MILDER CONTINENTAL POLAR AIR OVER THE MISSOURI
VALLEY. A SURFACE LOW WILL WEAKEN AS IT REACHES THE GREAT LAKES
SATURDAY...AND A WEAK TROUGH WILL PASS THROUGH THE CENTRAL PLAINS
AND INTO MISSOURI SUNDAY.

WPC NOTED OVERNIGHT THAT THE 00Z CANADIAN PRODUCED A MORE ROBUST
SURFACE REFLECTION TRACKING THROUGH MISSOURI AND CONTINUING INTO
ILLINOIS ON SUNDAY. ASIDE FROM THIS THE CANADIAN WAS CLOSE TO THE
GLOBAL MODEL CONSENSUS. THE 00Z UKMET WAS FLAT ALOFT...WHEREAS
THERE ARE GOOD INDICATIONS FROM THE OPERATIONAL MODELS AND
ENSEMBLES THAT A DEFINABLE TROUGH WILL CROSS THE NEW ENGLAND
STATES EARLY MONDAY. THE NAM/GFS/ECMWF GENERALLY SHOW THE MOST
SIMILARITY TO ONE ANOTHER WHILE PREDICTING A REASONABLE
PROGRESSION OF FEATURES SUPPORTED BY THE ENSEMBLE MEANS. THE NAM
BECOMES FAST ON DAY 3...BOTH OVER NEW ENGLAND AND UPSTREAM IN
CANADA...SO WE RECOMMEND DROPPING IT FROM THE BLEND AT THAT TIME.


...DEEP LOW TRACKING THROUGH CENTRAL CANADA MONDAY...

PREFERENCE: BLEND OF 12Z GFS WITH 00Z ECMWF/CANADIAN

MOST OF THE MODELS ARE POINTING TOWARD DEEP SURFACE LOW
DEVELOPMENT SUN/MON OVER CENTRAL CANADA AS A STRONG AND STRAIGHT
JET PUNCHES IN FROM THE WEST-NORTHWEST. ONLY THE 00Z UKMET WAS
WEAKER AT THE SURFACE AND ALOFT. THE ECMWF ENSEMBLE MEAN AND GEFS
MEAN HAVE BEEN FAIRLY STEADY FROM RUN TO RUN...AND THEIR HEIGHT
PATTERN WOULD PLACE THE GREATEST DIFLUENCE IN SUPPORT OF SURFACE
LOW DEVELOPMENT OVER CENTRAL MANITOBA BY MONDAY AFTERNOON. THE
GFS/GEFS SURFACE SOLUTIONS ARE SLIGHTLY FASTER THAN THE HEIGHT
PATTERN WOULD SUGGEST...BUT ARE SIMILAR ENOUGH TO THE ECMWF AND
CANADIAN TO BE BLENDED WITH THOSE MODELS. THE 12Z NAM WAS A FAST
OUTLIER. THIS SYSTEM MAY NOT BE A PRECIPITATION PRODUCER FOR THE
U.S. THROUGH DAY 3...BUT IT WILL INFLUENCE OTHER SENSIBLE WEATHER
SUCH AS WINDS OVER THE NORTHERN PLAINS AND UPPER MIDWEST.

...MODEL TREND GRAPHICS AT
www.wpc.ncep.noaa.gov/html/model2.shtml...

...500 MB FORECASTS AT
www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml...

BURKE
$$




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