Prognostic Meteorological Discussion
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000
FXUS10 KWNH 060448
PMDHMD

MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1147 PM EST THU MAR 05 2015

VALID MAR 06/0000 UTC THRU MAR 09/1200 UTC

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

...AN EVALUATION OF THE 00Z NAM/GFS ALONG WITH PRELIMINARY
PREFERENCES/FORECAST CONFIDENCE...

THERE DID NOT APPEAR TO BE ANY INITIALIZATION ERRORS WITH THE 00Z
NAM/GFS DEEMED SIGNIFICANT ENOUGH TO IMPACT THEIR FORECASTS.


...STRONG HEIGHT FALLS EXITING NEW ENGLAND EARLY FRIDAY MORNING...
...FRONTAL ZONE CROSSING THE SOUTHEASTERN U.S...

PRELIMINARY PREFERENCE: A NON-12Z CMC SOLUTION
FORECAST CONFIDENCE: ABOVE AVERAGE

A STRONG BAND OF HEIGHT FALLS ARE SEEN ON WATER VAPOR IMAGERY
MOVING EAST OF THE I-95 CORRIDOR. THE ENHANCED MOISTURE PLUME
ADVANCING AHEAD OF THIS UPPER TROF ARE CURRENTLY CROSSING THE
COASTAL CAROLINAS WHICH HAS GENERALLY BROUGHT AN END TO WIDESPREAD
PRECIPITATION ACROSS THE REGION. AS WAS THE CASE YESTERDAY...THE
12Z CMC WAS A LITTLE MORE AGGRESSIVE WITH THE EXTENT OF SURFACE
LOW PRESSURE OFFSHORE OF THE SOUTHEASTERN STATES. OTHERWISE...NO
MAJOR ISSUES ARE NOTED. WITH THAT SAID...WILL FAVOR A NON-12Z CMC
SOLUTION.


...SECONDARY SHORTWAVE MOVING THROUGH THE MID-ATLANTIC ON FRIDAY
NIGHT...

PRELIMINARY PREFERENCE: A NON-12Z UKMET MODEL COMPROMISE
FORECAST CONFIDENCE: ABOVE AVERAGE

ON THE WINGS OF THE DEEP UPPER TROF EXITING THE NORTHEASTERN U.S.
WILL BE A LOW AMPLITUDE SYSTEM CURRENTLY MOVING THROUGH THE MIDDLE
MS VALLEY. EARLY IN THE FORECAST...THE 12Z UKMET IS A TAD QUICKER
SPREADING WEAK HEIGHT FALLS THROUGH THE MID-ATLANTIC REGION. WHILE
SUBTLE IN NATURE...IT STILL DOES DEPART FROM THE MODEL CONSENSUS.
THUS...THE RECOMMENDATION IS A NON-12Z UKMET MODEL COMPROMISE.


...SERIES OF SHORTWAVES RACING THROUGH THE GREAT
LAKES/NORTHEASTERN U.S...
...SURFACE CYCLONE REACHING THE UPPER GREAT LAKES BY SATURDAY
MORNING...

PRELIMINARY PREFERENCE: A NON-12Z CMC MODEL COMPROMISE
FORECAST CONFIDENCE: AVERAGE

BROAD CYCLONIC FLOW WILL CONTINUE TO ANCHOR MUCH OF THE
NORTHEASTERN SECTOR OF THE CONTINENT. THIS IS FORECAST TO SPREAD A
SERIES OF SHORTWAVES FROM CENTRAL CANADA DOWN THROUGH THE GREAT
LAKES AND INTO THE NORTHEASTERN U.S. FROM SATURDAY INTO EARLY NEXT
WEEK. THE UPPER FLOW DOES BEGIN TO RELAX AS THE PERIOD PROGRESSES
WHICH SUGGESTS MODERATION IN THE TEMPERATURE PATTERN. AS A
WHOLE...MOST OF THESE SYSTEMS WILL BE RATHER BENIGN IN NATURE
EXCEPT FOR THE INITIAL IMPULSE WHICH CARRIES A MODEST SURFACE LOW
ACROSS THE UPPER GREAT LAKES EARLY SATURDAY. RELATIVE TO THE
GUIDANCE YESTERDAY...THE MODELS ARE CLUSTERING MORE WITH THE
TIMING AND STRENGTH OF THIS CYCLONE. IT APPEARS THE TREND HAS BEEN
IN THE STRONGER DIRECTION AS THE ECMWF SUITE WAS THE ONLY SOLUTION
FAVORING A MORE DEFINED SYSTEM. MORE OF THE UNCERTAINTY LIES WITH
THE PATTERN UPSTREAM AS ADDITIONAL SHORTWAVES MOVE THROUGH THE
NORTHERN TIER. THE 12Z CMC IS MORE DEVELOPED WITH A POSSIBLE
SURFACE LOW OVER THE MIDDLE MS VALLEY ON SUNDAY MORNING WHICH AIDS
IN HIGHER QPF AMOUNTS ON DAY 2. ITS SOLUTION CONTINUES TO REMAIN
MORE AGGRESSIVE INTO THE FOLLOWING DAY. OVERALL...WHILE GENERAL
TIMING DIFFERENCES ARE NOTED IN THE PROGRESSIVE NORTHERN STREAM
FLOW...THESE ARE SMALL ENOUGH TO FAVOR A NON-12Z CMC MODEL
COMPROMISE.


...UPPER LOW SPINNING OVER THE NORTHERN GULF OF BAJA CA/SEA OF
CORTEZ...

PRELIMINARY PREFERENCE: BLEND OF THE 12Z ECMWF/CMC WITH THE 12Z
ECMWF ENSEMBLE MEAN
FORECAST CONFIDENCE: AVERAGE

A REX BLOCK WILL BE IN PLACE TO COMMENCE THE PERIOD ACROSS THE
WEST COAST AS A COMPACT UPPER LOW MOVES TOWARD BAJA CA. THE RIDGE
TO THE NORTH SHOULD REMAIN IN ITS POSITION ANCHORING THE CENTRAL
GREAT BASIN WHILE THE CLOSED LOW SLOWLY MOVES TOWARD THE NORTHERN
GULF OF BAJA CA/SEA OF CORTEZ BY LATE FRIDAY. MODELS VARY WITH HOW
QUICKLY THIS FEATURE EVOLVES INTO AN OPEN WAVE MOVING TOWARD FAR
WEST TX. AT THIS TIME...THE 00Z NAM/18Z GEFS MEAN ARE THE QUICKEST
SOLUTIONS WHILE THE 12Z UKMET/21Z SREF MEAN CONTINUE TO BE THE
SLOWEST PLAYERS. WILL PLAY THE CENTER OF THE SPREAD WHICH FAVORS A
COMBINATION OF THE 12Z ECMWF/CMC WHILE ALSO INCLUDING THE 12Z
ECMWF ENSEMBLE MEAN GIVEN THE GROWING MODEL UNCERTAINTY.



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

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

RUBIN-OSTER

$$




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