Prognostic Meteorological Discussion
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FXUS10 KWNH 301602
PMDHMD

MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1059 AM EST FRI JAN 30 2015

VALID JAN 30/1200 UTC THRU FEB 03/0000 UTC

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

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


...UPPER TROUGH GOING NEGATIVE TILT OVER NEW ENGLAND LATER TODAY
AND TONIGHT...
...STRENGTHENING COASTAL LOW...

PREFERENCE: GENERAL MODEL COMPROMISE
CONFIDENCE: ABOVE AVERAGE

CURRENT WATER VAPOR IMAGERY SHOWS A DEEP UPPER TROUGH BEGINNING TO
GO NEGATIVE TILT ACROSS THE NORTHERN MID-ATLANTIC AND SOUTHERN NEW
ENGLAND. THE MODELS ADVERTISE SURFACE LOW PRESSURE REDEVELOPING
NEAR THE BENCHMARK TODAY AND THEN DEEPENING TO SOUTHWEST OF NOVA
SCOTIA BY EARLY SAT AS THE TROUGH CLOSES OFF ALOFT. THE TREND IN
THE GUIDANCE OVER THE LAST DAY OR SO HAS BEEN TO SHIFT THE
REDEVELOPING LOW CENTER A LITTLE FARTHER OFFSHORE. THE 12Z NAM AND
12Z GFS SUPPORT THE CURRENT GLOBAL MODEL CONSENSUS. SO...A GENERAL
MODEL COMPROMISE WILL BE FAVORED AT THIS POINT.


...ELONGATED UPPER TROUGH AND CLOSED LOW IMPACTING THE SOUTHWEST
AND NORTHWEST MEXICO...

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

ALL OF THE MODELS SHOW AN ELONGATED N/S TROUGH AXIS FROM SOUTHERN
CA SOUTH DOWN TO JUST WEST OF THE BAJA PENINSULA WITH MULTIPLE
EMBEDDED VORT CENTERS. THE MOST SIGNIFICANT OF WHICH IS OVER
SOUTHERN CA CURRENTLY. WV/IR SAT IMAGERY SHOWS A WELL-DEFINED
SUBTROPICAL MOISTURE CONNECTION ASSOCIATED WITH THE TROUGH...AND
THE GUIDANCE BRINGS A LARGE AMOUNT OF VORT ENERGY AND MOISTURE
INTO THE SOUTHWEST OVER THE NEXT COUPLE OF DAYS. THIS ENERGY WILL
ADVANCE EAST AND DEEPEN INTO A FAIRLY BROAD CLOSED UPPER LOW BY
LATER TODAY OVER THE SOUTHWEST. 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 STRONGER MODEL
CLUSTERING AT THIS POINT STILL FAVORS A BLEND OF THE 12Z GFS AND
00Z ECMWF...WHICH IS SUPPORTED BY THE GEFS MEAN AND ECENS MEAN.
THE 12Z NAM AND 00Z UKMET ARE STRONGER THAN THE MULTI-MODEL
CONSENSUS BY LATER SUN AND MON...WITH THE UKMET DISPLACED FARTHEST
WEST. WILL FAVOR A BLEND OF THE GFS AND ECMWF.


...SHORTWAVE ENERGY AMPLIFYING FROM THE MID MS VALLEY TO THE
MID-ATLANTIC STATES...
...ASSOCIATED SURFACE LOW...

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

A SHORTWAVE NOW ENTERING CENTRAL BRITISH COLUMBIA WILL BE DIGGING
SOUTHEAST DOWN INTO THE NORTHERN/CENTRAL PLAINS LATER SAT AND INTO
SUN. THIS ENERGY COUPLED WITH A MORE SUBTLE SHORTWAVE ON ITS HEELS
DROPPING DOWN FROM THE NORTHWEST TERRITORIES WILL PLAY A KEY ROLE
IN THE EVOLUTION OF SURFACE LOW PRESSURE THAT IS CURRENTLY
FORECAST TO DEVELOP OVER THE LOWER MO AND MID MS VALLEY REGION BY
EARLY SUN BEFORE THEN AIMING EAST TOWARD THE OH VALLEY AND
MID-ATLANTIC STATES SUN NIGHT AND MON.

AS WAS THE CASE YESTERDAY...THE QUICKER AND MORE AMPLIFIED 00Z
UKMET SUPPORTS SURFACE LOW DEVELOPMENT THAT IS MORE DEFINED AND
NORTH OF THE MODEL ENVELOPE. THE 00Z GEM IS NOTABLY FLATTER AND
SUPPORTS ITS SURFACE LOW DEVELOPMENT DOWN TOWARD THE LOWER MS
VALLEY AND THE GULF COAST STATES THROUGH THE PERIOD. THE 12Z NAM
AFTER ABOUT 36 HRS SUGGESTS A STRONGER/SHARPER SHORTWAVE TROUGH
AND A LOW TRACK NORTH OF THE MULTI-MODEL CONSENSUS. THE 09Z SREF
MEAN GENERALLY FAVORS THE NAM DETERMINISTIC SOLUTION.
HOWEVER...THE STRONGEST MODEL CLUSTERING AND ESSENTIALLY THE
GLOBAL MODEL CONSENSUS FAVORS THE 12Z GFS AND 00Z ECMWF...WHICH
ARE WELL SUPPORTED BY THEIR RESPECTIVE ENSEMBLE MEANS PER THE GEFS
AND ECENS MEANS. WILL FAVOR A BLEND OF THE GFS AND ECMWF AS A
RESULT...BUT CONFIDENCE WILL REMAIN LIMITED GIVEN THE SIGNIFICANT
LATITUDINAL SPREAD SEEN IN THE GUIDANCE ACROSS ESPECIALLY THE OH
VALLEY AND MID-ATLANTIC REGIONS...WITH THE UKMET AND TO A LESSER
EXTENT THE NAM FARTHER NORTH...AND THE GEM VERY SUPPRESSED. THE
GFS AND ECMWF OFFER A NICE COMPROMISE FOR NOW.


...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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