Prognostic Meteorological Discussion
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000
FXUS10 KWNH 020731
PMDHMD

MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
331 AM EDT THU OCT 02 2014

VALID OCT 02/0000 UTC THRU OCT 05/1200 UTC

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

==============================================
00Z MODEL EVALUATION AND PREFERENCES
==============================================
NAM/GFS INITIALIZATION ERRORS DO NOT APPEAR TO
SIGNIFICANTLY AFFECT THEIR LARGE SCALE OUTPUT.
==============================================

...LARGE AND POWERFUL CYCLONE TO BECOME CENTERED OVER THE GREAT
LAKES...
...EFFECTS REACHING ALL THE CENTRAL AND EASTERN U.S...

PREFERENCE: BLEND OF 00Z NAM/GFS/CANADIAN
CONFIDENCE: AVERAGE

A TROUGH EMERGING FROM THE SOUTHERN ROCKIES AND PLAINS WILL
UNDERGO STRONG CYCLOGENESIS OVER THE GREAT LAKES. A STRONG FRONT
WILL DRY OUT THE LOW LEVELS IN THE CENTRAL AND EASTERN U.S. ALL
THE WAY TO FAR SOUTH TX AND FL BY SATURDAY. THE ASSOCIATED UPPER
TROUGH DIPS TO 3 OR 3.5 DEVIATIONS BELOW CLIMATOLOGY WHILE EQUALLY
ANOMALOUS 850 MB TEMPERATURES OVERSPREAD THE EASTERN AND SOUTHERN
U.S...LIKELY LEADING TO SOME FROST CONCERNS FROM THE GREAT LAKES
TO PERHAPS AS FAR SOUTH AS THE TENNESSEE VALLEY. ALL OF THE MODELS
PREDICT A SIMILAR BREADTH AND MAGNITUDE OF COLD AIR TO SPILL INTO
THE U.S. AT 850-700 MB.

MODELS ARE SIMILAR...AS WOULD BE EXPECTED WITH SUCH A LARGE SCALE
AND CLASSICALLY ORGANIZED SYSTEM.
THERE ARE SOME DETAIL DIFFERENCES...HOWEVER...ESPECIALLY NEAR THE
SURFACE. JET COUPLING IS MAXIMIZED LEADING UP TO 04/00Z WHEN ONE
WOULD EXPECT AN INTENSE CYCLONE OVER SOUTHERN OR CENTRAL ONTARIO.
THE NAM AND CANADIAN ARE CLOSEST TO OUR CONCEPTUAL MODEL...BUT THE
NAM IS SLOW WITH THE TRAILING FRONTAL BOUNDARY THAT SHOULD SURGE
THROUGH THE EASTERN U.S. THE GFS SURFACE LOW IS FARTHER NORTH
DURING THE MATURING STAGE OF THE CYCLONE...WHILE THE ECMWF DELAYS
ITS MATURATION AT THE SURFACE AND REMAINS SOUTH OF THE OTHER
OPERATIONAL MODELS. THESE DIFFERENCES ARE IMPORTANT MAINLY TO THE
FORECAST FOR SOUTHERN CANADA AND THE GREAT LAKES STATES. THE
NAM/GFS/CANADIAN BEST FIT OUR CONCEPTUAL MODEL...BUT THERE ARE NO
TRUE OUTLIERS.


...UPPER LOW PULLING AWAY FROM NEW ENGLAND...

PREFERENCE: BLEND OF THE OPERATIONAL MODELS...LESS WEIGHT ON THE
NAM
CONFIDENCE: AVERAGE

THE LOW WILL HAVE DECREASING INFLUENCE ON THE WEATHER ALONG THE
NEW ENGLAND COAST THROUGH FRIDAY. CONFIDENCE IS ONLY
AVERAGE...HOWEVER...GIVEN THAT THIS IS A SMALLER SCALE CLOSED LOW
EMBEDDED WITHIN SHORTWAVE RIDGING. JUDGING BY MODEL
AGREEMENT...NEARLY ANY MODEL COULD BE USED FOR THIS SYSTEM. THE
CANADIAN SOLUTION MOVED MORE TO THE MIDDLE OF THE PACK. THE NAM
MOVES THE SYSTEM A LITTLE MORE QUICKLY TO THE SOUTH AND EAST...AND
SHOULD RECEIVE LESS WEIGHT OVER TIME.


...SHORTWAVE BRUSHING THE PACIFIC NORTHWEST FRI/SAT...

PREFERENCE: ANY OF THE OPERATIONAL MODELS
CONFIDENCE: ABOVE AVERAGE

A PACIFIC TROUGH WILL DE-AMPLIFY AS IT MOVES INTO THE MEAN RIDGE
POSITION ACROSS BRITISH COLUMBIA FRIDAY. THE TROUGH WILL CARRY A
MINIMAL INCREASE OF MOIST ONSHORE FLOW WITH IT...POSSIBLY BRINGING
LIGHT PRECIPITATION WESTERN WASHINGTON AND POSSIBLY THE HIGHER
PEAKS IN THE NORTHERN ROCKIES. MODEL DEPICTIONS ARE SIMILAR TO ONE
ANOTHER.

...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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