Prognostic Meteorological Discussion
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FXUS10 KWNH 291627
PMDHMD

MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1127 AM EST THU JAN 29 2015

VALID JAN 29/1200 UTC THRU FEB 02/0000 UTC

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

12Z MODEL EVALUATION...INCLUDING THE NAM AND GFS

...PAIR OF SHORTWAVES CROSSING THE OH VALLEY...
...NEGATIVELY TILTING TROUGH IMPACTING THE NORTHEAST...
...SURFACE LOWS PHASING OVER NEW ENGLAND...

PREFERENCE: BLEND OF THE 12Z GFS/00Z ECMWF AND 00Z UKMET
CONFIDENCE: SLIGHTLY ABOVE AVERAGE

THE LATEST WATER VAPOR IMAGERY CONTINUES TO SHOW A PAIR OF
DISTINCT SHORTWAVE IMPULSES TRACKING THROUGH THE MID MS VALLEY AND
TOWARD THE OH VALLEY. THE CORRESPONDING SURFACE WAVES WILL BOTH
MIGRATE EASTWARD THROUGH THE OH VALLEY AND LOWER GREAT LAKES
REGION THROUGH TONIGHT. MEANWHILE...WITH THE INTRUSION OF
ADDITIONAL NORTHERN STREAM ENERGY FROM THE GREAT LAKES
REGION...THE GUIDANCE DEPICTS A LARGER SCALE TROUGH AMPLIFYING AND
GOING NEGATIVE TILT OVER NEW ENGLAND FRI...WITH A CLOSED LOW THEN
DEVELOPING JUST OFFSHORE SOUTHERN NEW ENGLAND BY FRI NIGHT. THE
STRONG HEIGHT FALLS/DYNAMICS WILL ALLOW SURFACE LOW PRESSURE TO
REDEVELOP NEAR LONG ISLAND BY FRI MORNING AND THEN INTENSIFY INTO
THE GULF OF MAINE BY EARLY SAT.

THE 12Z NAM AND 00Z GEM ARE RELATIVELY STRONGER SOLUTIONS COMPARED
TO THE 12Z GFS/00Z ECMWF AND 00Z UKMET. THE NAM AND GEM TUCK LOW
PRESSURE IN JUST A LITTLE CLOSER TO THE COAST OF MAINE LATER FRI
NIGHT AND EARLY SAT AS A RESULT VERSUS THE GFS/ECMWF AND UKMET.
THE NEW GFS IS IN BETTER AGREEMENT WITH THE 00Z ECENS AND 00Z GEM
ENSEMBLE LOW CLUSTERS VERSUS THE 00Z GEFS MEMBERS.
THEREFORE...THERE IS A STRONGER SIGNAL FOR THE LOW CENTER
DEVELOPING OFFSHORE NEW ENGLAND TO BE JUST A TAD FARTHER OFFSHORE
VERSUS THE NAM/GEM DETERMINISTIC OUTPUT. WILL FAVOR A BLEND OF THE
12Z GFS/00Z ECMWF AND 00Z UKMET AS A RESULT WHICH HAVE THE
STRONGER ENSEMBLE CLUSTERING SUPPORT.


...BROAD TROUGH/CLOSED LOW IMPACTING THE SOUTHWEST/FOUR CORNERS
REGION...

PREFERENCE: BLEND OF THE 12Z GFS AND 00Z ECMWF
CONFIDENCE: ABOVE AVERAGE

ALL OF THE MODELS SHOW AN ELONGATED N/S TROUGH AXIS OFFSHORE
CALIFORNIA WHICH STRETCHES DOWN INTO THE SUBTROPICS WEST OF THE
BAJA PENINSULA. THIS ENERGY IS FORECAST TO LIFT EAST-NORTHEAST AND
DEEP INTO A FAIRLY BROAD CLOSED UPPER LOW BY MIDDAY FRI OVER
SOUTHERN CA. ON SAT AND SUN...THE ENERGY THEN GETS SUPPRESSED
SOUTHWARD INTO NORTHWEST MEXICO AND THE ADJACENT BAJA PENINSULA IN
RESPONSE TO STRONG NORTHWESTERLY NORTHERN STREAM FLOW OVER THE
CENTRAL AND NORTHERN ROCKIES. THE GLOBAL MODELS ARE IN GOOD
AGREEMENT ON THE LARGER SCALE WITH THE EVOLUTION OF THESE HEIGHT
FALLS. A GENERAL MODEL COMPROMISE LED BY A BLEND OF THE 12Z GFS
AND 00Z ECMWF WILL BE FAVORED.


...HEIGHT FALLS MOVING THROUGH THE CENTRAL U.S. SAT AND SUN...
...FRONTAL ZONE SINKING SOUTHWARD...

PREFERENCE: BLEND OF THE 12Z GFS AND 00Z ECMWF
CONFIDENCE: AVERAGE

THE MODELS SHOW AN AREA OF HEIGHT FALLS DIGGING THROUGH THE
NORTHERN HIGH PLAINS BY MIDDAY SAT WHICH BEGINS TO AMPLIFY A BIT
MORE THROUGH SUN INTO THE MIDWEST. THIS WILL SEND A COLD FRONT
SOUTHEAST ACROSS THE REGION AS WELL. THE 00Z GEM AND ESPECIALLY
THE 00Z UKMET ARE DEEPER OUTLIERS. THE 12Z NAM/12Z GFS AND 00Z
ECMWF ARE FLATTER BUT HAVE STRONGER ENSEMBLE SUPPORT FROM THE SREF
MEAN/GEFS MEAN AND ECENS MEAN. THE NAM MAY BE A LITTLE TOO SHARP
OVER THE CENTRAL PLAINS BY SUN...AND SO BASED ON THE CURRENT
CLUSTERING AND ENSEMBLE SUPPORT...A BLEND OF THE GFS AND ECMWF
WILL BE PREFERRED.


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

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

ORRISON

$$





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