Prognostic Meteorological Discussion
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FXUS10 KWNH 211700
PMDHMD

MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1259 PM EDT MON JUL 21 2014

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

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

12Z NAM/GFS EVALUATION...INCLUDING PRELIMINARY PREFERENCES


MID-LEVEL LOW SLOWLY RETROGRADING OVER THE GULF COAST STATES
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL COMPROMISE
CONFIDENCE: SLIGHTLY ABOVE AVERAGE

THE GUIDANCE IS IN DECENT AGREEMENT WITH THE DETAILS OF A
MID-LEVEL LOW OVER THE SOUTHEAST...FORECAST TO SLOWLY RETROGRADE
AND SHEAR IN A SW-NE ORIENTED FASHION BY THU. THE BIGGEST
DIFFERENCES ARE WITH THE LOCATION OF THIS SHEAR AXIS IN THE WRN
GULF OF MEXICO. THE 12Z NAM/GFS OFFER A DECENT COMPROMISE OF
POSITION AND STRENGTH BUT ANY MODEL APPEARS POSSIBLE DOWN ACROSS
THIS REGION SO A GENERAL COMPROMISE WILL BE PREFERRED.


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 00Z UKMET COMPROMISE
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.


MID-LEVEL SHORTWAVE EJECTING ENEWD INTO THE DAKOTAS THIS AFTERNOON
DEVELOPING SURFACE LOW MOVING THROUGH THE UPPER MISS VALLEY
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 00Z ECMWF...00Z CMC COMPROMISE
CONFIDENCE: AVERAGE

IT APPEARS THE 12Z NAM AND GFS HAVE A BETTER HANDLE ON THE TIMING
OF THE SHORTWAVE CURRENTLY MOVING INTO THE WRN DAKOTAS...MATCHING
UP BETTER WITH WV IMAGERY AND SHORT TERM MODEL FORECASTS FROM THE
RAP AND HRRR...TO BE SLIGHTLY SLOWER THAN THE 00Z ECMWF/UKMET/CMC.
HOWEVER...ONCE CONVECTION GETS UNDERWAY TONIGHT ACROSS THE DAKOTAS
INTO MINNESOTA...THESE INITIAL SHORTWAVE TIMING DIFFERENCES BECOME
LESS IMPORTANT.

THE 12Z NAM BECOMES SIGNIFICANTLY SLOWER WITH THE SURFACE LOW
MOVING ACROSS LAKE SUPERIOR TONIGHT WHILE THE 00Z UKMET LIKELY
DEVELOPS CONVECTIVE FEEDBACK WITH A FASTER/STRONGER SURFACE LOW
RACKING ACROSS SRN ONTARIO. THE 12Z GFS ENDS UP MUCH FASTER WITH A
COLD FRONT TRACKING THROUGH THE OHIO VALLEY BUT THE 00Z ECMWF AND
00Z CMC APPEAR TO AFFORD A DECENT COMPROMISE IN LINE WITH THE
MEANS AND RUN TO RUN CONTINUITY.


...MODEL TREND GRAPHICS AT
www.wpc.ncep.noaa.gov/html/model2.shtml...
...500 MB FORECASTS AT
www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml...

OTTO

$$





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