Prognostic Meteorological Discussion
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000
FXUS10 KWNH 210640
PMDHMD

MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
239 AM EDT MON JUL 21 2014

VALID JUL 21/0000 UTC THRU JUL 24/1200 UTC

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

00Z MODEL EVALUATION...INCLUDING THE NAM/GFS/UKMET/GEM AND ECMWF


...SHORTWAVE TROUGH LIFTING THROUGH THE NORTHEAST...
...BROAD WEAK TROUGH/CLOSED LEFT BEHIND OVER THE TN VALLEY/GULF
COAST STATES...

PREFERENCE: GENERAL MODEL COMPROMISE
CONFIDENCE: ABOVE AVERAGE

THE GUIDANCE IS IN VERY GOOD AGREEMENT WITH THE DETAILS OF THE
EXITING SHORTWAVE TROUGH MOVING THROUGH THE NORTHEAST AND ALSO
WITH THE DETAILS OF WHAT SHOULD BE A BROAD UPR TROUGH AND WEAK
CLOSED LOW OVER THE TN VLY AND GULF COAST STATES THROUGH THE
MIDDLE OF THE WEAK. A GENERAL MODEL COMPROMISE WILL BE FAVORED AS
A RESULT.


...DEEP UPPER TROUGH/CLOSED LOW OVER THE GULF OF AK DROPPING INTO
THE NORTHWEST...
...SURFACE LOW PRESSURE DEVELOPING IN THE LEE OF THE NORTHERN
ROCKIES...

PREFERENCE: NON-UKMET CONSENSUS
CONFIDENCE: ABOVE AVERAGE

OVERALL THE MODELS ARE IN EXCELLENT AGREEMENT ON DROPPING A CLOSED
LOW AND ASSOCD UPR TROUGH DOWN FROM THE GULF OF AK THE NEXT COUPLE
OF DAYS AND SWINGING IT INTO THE PAC NORTHWEST BY LATE WED. THE
ONE MODEL THAT APPEARS AS AN OUTLIER IS THE 00Z UKMET BY WED AND
THURS WHEN IT SUGGESTS A NOTABLY MORE PROGRESSIVE TROUGH CROSSING
THE NORTHWEST AND IMPACTING SOUTHWEST CANADA. THESE HEIGHT FALLS
ARE EXPECTED TO INDUCE LEESIDE CYCLOGENESIS OVER THE HIGH PLAINS
OF ALBERTA AND ALSO ERN MT BY EARLY THURS AND THERE IS VERY GOOD
CLUSTERING WITH SURFACE LOW PLACEMENT...ALTHOUGH AGAIN THE UKMET
WAS SEEN BEING A BIT MORE PROGRESSIVE. GIVEN THE STRONG MODEL
CLUSTERING SEEN OTHERWISE...WILL PREFER A NON-UKMET CONSENSUS FOR
THIS SYS.


...WEAK MID/UPPER LEVEL LOW SHEARING NORTH AND NORTHEAST OUT OF
CA...
...SURFACE LOW DEVELOPING IMPACTING THE NORTHERN PLAINS/UPPER
MIDWEST MON AND TUE...

PREFERENCE: 00Z ECMWF
CONFIDENCE: AVERAGE

THE MODELS INDICATE THAT THE WEAK UPR LOW CURRENTLY SHEARING NWD
ACROSS CA WILL WEAKEN FURTHER AND WITH A PORTION OF THE ENERGY
THEN ADVANCING NEWD AND EWD AND THE N SIDE OF WHAT WILL BE A
STRENGTHENING SUBTROPICAL RIDGE OVER THE FOUR CORNERS REGION AND
SRN PLAINS MON AND TUES. THE ENERGY WILL REACH THE NRN PLAINS AND
UPR MS VLY BY LATER TUES AND WILL FOSTER A DEVELOPING SFC LOW THAT

WILL ADVANCE EAST AND MOVE INTO THE GRT LAKES REGION ALONG WITH A
COLD FRONT BY EARLY WED. THE COLD FRONT WILL ARRIVE ALONG THE
EASTERN SEABOARD ON THURS. THE 00Z UKMET SOLN IS THE FASTEST AND
FARTHEST NORTH WITH RESPECT TO THE SFC LOW. THE 00Z GFS INITIALLY
IS THE SLOWEST AND FARTHEST SOUTH...ALTHOUGH IT DOES REDEVELOP LOW
PRESSURE CLOSER INTO THE GLOBAL MODEL CONSENSUS OVER ONTARIO AND
QUEBEC BY 48 HRS AND ONWARD. THE GFS IS ALSO NOTED TO BE SUFFERING
FROM SOME CONVECTIVE FEEDBACK. THE 00Z NAM/00Z GEM AND 00Z ECMWF
CLUSTERED PRETTY WELL IN BETWEEN AT LEAST EARLY ON...BUT BY DAYS 2
AND 3...THE 00Z NAM AND 00Z GEM BECOME THE SLOWEST SOLNS WITH THE
00Z GFS/00Z UKMET SOLNS THE FASTEST AND THE 00Z ECMWF SPLITTING
THE DIFF. GIVEN RATHER STRONG RUN TO RUN CONTINUITY ON THE
ECMWF...WILL PREFER THE 00Z ECMWF.


...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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