Prognostic Meteorological Discussion
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000
FXUS10 KWNH 301838
PMDHMD

MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
137 PM 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/GFS/UKMET/GEM AND THE
ECMWF


...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 12Z ECMWF...THROUGH 48 HOURS
            12Z GFS...48 HOURS TO 84 HOURS
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 12Z NAM IS A BIT
STRONGER THAN THE MULTI-MODEL CONSENSUS BY LATER SUN AND MON. THE
12Z UKMET AND 12Z ECMWF HAVE THEIR RESPECTIVE LOW CENTERS SQUASHED
A BIT FARTHER SOUTH AND EVEN A LITTLE SOUTHWEST OF THE GLOBAL
MODEL CONSENSUS BY THE END OF THE PERIOD. THE STRONGER MODEL
CLUSTERING TENDS TO FAVOR A BLEND OF THE 12Z GFS AND 12Z ECMWF
THROUGH ABOUT 48 HOURS...AND THEN MORE TOWARD THE GFS THEREAFTER.
THE 12Z GEM FAVORS CLUSTERS REASONABLY WELL WITH THE 12Z GFS. WILL
SUGGEST A 12Z GFS/12Z ECMWF BLEND THROUGH 48 HOURS...AND THEN THE
12Z GFS THEREAFTER THROUGH THE REMAINDER OF THE SHORT RANGE PERIOD.


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

PREFERENCE: BLEND OF THE 12Z GFS AND 12Z 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 12Z
UKMET SUPPORTS SURFACE LOW DEVELOPMENT THAT IS STRONGER AND NORTH
OF THE MODEL ENVELOPE. THE 12Z NAM AFTER ABOUT 36 HRS SUGGESTS A
STRONGER/SHARPER SHORTWAVE TROUGH AND A LOW TRACK NORTH OF THE
MULTI-MODEL CONSENSUS AS WELL...BUT NOT TO THE EXTENT OF THE
UKMET. THE 09Z SREF MEAN GENERALLY FAVORS THE NAM DETERMINISTIC
SOLUTION. THE 00Z GEM WAS NOTABLY FLATTER AND SUPPORTED ITS
SURFACE LOW DEVELOPMENT DOWN TOWARD THE LOWER MS VALLEY AND THE
GULF COAST STATES THROUGH THE PERIOD. HOWEVER...THE 12Z GEM HAS
TRENDED WELL NORTH AND ACTUALLY IS VERY CLOSE TO THE WELL
CLUSTERED 12Z GFS AND 12Z ECMWF SOLUTIONS. THE GEM/GFS AND ECMWF
CLUSTER IS SUPPORTED BY THE LATEST GEFS MEAN AND ECENS MEAN AS
WELL. WILL FAVOR A BLEND OF THE GFS AND ECMWF AS A RESULT...BUT
CONFIDENCE WILL STILL REMAIN LIMITED FOR AT LEAST THIS CYCLE GIVEN
THAT THERE ARE STILL FAIRLY SIGNIFICANT LATITUDINAL DIFFERENCES
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 THERE STILL BEING A BIT OF SCATTER WITHIN
THE GEFS AND ECENS LOW PLOTS.


...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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