Prognostic Meteorological Discussion
Issued by NWS

000
FXUS10 KWNH 211820
PMDHMD

MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
219 PM EDT TUE MAY 21 2013

VALID MAY 21/1200 UTC THRU MAY 25/0000 UTC

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


FINAL 12Z MODEL EVALUATION WITH MODEL PREFERENCES
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
NAM/GFS INITIALIZATION ERRORS DO NOT SEEM TO DEGRADE THEIR SHORT
RANGE FORECASTS.


DEEP CYCLONE OVER THE NORTHWEST
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: MODEL BLEND

THE GUIDANCE IS IN VERY GOOD AGREEMENT THAT THE CLOSED 500MB LOW
CENTER ARRIVING INTO THE NW WILL REMAIN STATIONARY OVER THE NEXT
THREE DAYS AND STEER A POTENT SHORT WAVE TROUGH THROUGH NRN CA/NV
INTO THE NRN ROCKIES/PLAINS. DO NOT SEE MUCH SPREAD HERE OTHER
THAN PERHAPS THE 00Z/21 ECMWF BEING A BIT SLOWER ON THE SHORT WAVE
LIFTING UP INTO THE MT/NRN PLAINS LATE IN THE FCST PERIOD. EXPECT
AN ANOMALOUS COLD FRONT TO SWEEP THROUGH THE NW AND REACH THE
FRONT RANGE OF THE NRN ROCKIES INTO ERN MT/WY AND WRN ND/SD BY THE
END OF THE FCST PERIOD.


LARGE SYSTEM MOVING FROM THE MIDWEST TO THE EAST
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 00Z/21 ECMWF/EC MEAN AND 12Z UKMET

THE 12Z GFS APPEARS TO BE A SLOW OUTLIER ON THE PROGRESSION OF THE
DYNAMIC SRN STREAM TROUGH AND ITS INTERACTION WITH THE DIGGING NRN
STREAM THROUGHOUT THE FCST PERIOD. THE GFS DEVELOPS THIS CLOSED
500MB LOW CENTER OVER NERN OH AROUND 72 HRS... PERHAPS POSSIBLE
FEEDBACK OR OVER-INTENSIFYING THE SYSTEM ALOFT AND THIS HALTS THE
PROGRESSION OF THE SYSTEM LIFTING UP THE EAST COAST. THE 00Z/21
ECMWF/EC MEAN AND 12Z UKMET/NAM APPEAR MORE IN LINE ON THE SRN
STREAM TROUGH REACHING THE OH/TN VLYS OVER THE NEXT 36 HRS...
AHEAD OF THE DIGGING NRN STREAM TROUGH/COLD FRONT DROPPING INTO
THE UPPER LAKES. THE TWO SYSTEMS THEN PARTIALLY INTERACT OR
PHASE... AS THE SURFACE COLD FRONT PUSHES OFF THE EAST COAST AND A
WAVE OF LOW PRESSURE PUSHES THROUGH THE NORTHEAST. WPC WILL FAVOR
THE AFOREMENTIONED CONSENSUS WHICH ALSO HAS SUPPORT FROM THE 12Z
ECMWF.


UPPER LOW/TROUGH OVER FLORIDA
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: MODEL BLEND

THE 12Z GUIDANCE ALL GENERALLY AGREE THAT THE MID-LEVEL LOW/UPPER
TROUGH STARTING OFF OVER FL WILL GRADUALLY FILL AND LIFT TO THE
NORTH AND EAST... AS THE UPSTREAM POWERHOUSE TROUGH BEGINS TO
PROGRESS INTO THE EAST.


...MODEL TREND GRAPHICS AT
WWW.WPC.NCEP.NOAA.GOV/HTML/MODEL2.SHTML...
...500 MB FORECASTS AT WWW.WPC.NCEP.NOAA.GOV/H5PREF/H5PREF.SHTML...

MUSHER

$$