Prognostic Meteorological Discussion
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FXUS10 KWNH 311832
PMDHMD

MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
231 PM EDT THU JUL 31 2014

VALID JUL 31/1200 UTC THRU AUG 04/0000 UTC

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

...AN EVALUATION OF THE 12Z CMC/UKMET/ECMWF ALONG WITH PRELIMINARY
PREFERENCES/FORECAST CONFIDENCE...

THERE DID NOT APPEAR TO BE ANY INITIALIZATION ERRORS WITH THE 12Z
NAM/GFS DEEMED SIGNIFICANT ENOUGH TO IMPACT THEIR FORECASTS.


...MEAN TROF CONTINUING TO ANCHOR THE EASTERN U.S...
...COASTAL BAROCLINIC ZONE...

FINAL PREFERENCE: BLEND OF THE 12Z ECMWF/00Z ECMWF ENSEMBLE MEAN
FORECAST CONFIDENCE: SLIGHTLY BELOW AVERAGE

A PERSISTENT LONGWAVE TROF POSITIONED ACROSS THE EASTERN PORTION
OF THE CONUS WILL REMAIN ANOMALOUS IN NATURE THROUGH THE WEEKEND.
500-MB HEIGHT ANOMALIES ARE FORECAST TO BE ABOUT 2 STANDARD
DEVIATIONS BELOW CLIMATOLOGY. WITHIN THE NORTHWESTERLY FLOW ON THE
WESTERN FRINGE OF THE BROAD CIRCULATION...A NUMBER OF IMPULSES
WILL SLIDE THROUGH THE CENTER OF THE COUNTRY AND EVENTUALLY
MATERIALIZE ACROSS THE DEEP SOUTH/SOUTHEASTERN U.S. EVENTUALLY THE
EASTERN EXTENT OF THE UPPER TROF BEGINS TO DRIFT WESTWARD AS A
594-DM ATLANTIC RIDGE BEGINS TO ADVANCE TOWARD THE WEST. BY
03/0000Z...THE 12Z NAM/09Z SREF MEAN AND 12Z GFS/GEFS MEAN ARE
WEST OF THE 12Z CMC/UKMET WHILE THE 12Z ECMWF/00Z ECMWF ENSEMBLE
MEAN SIT SOMEWHERE IN THE MIDDLE WITH REGARD TO THE EASTERN
PLACEMENT OF THE UPPER TROF. THIS SPREAD HAS LARGE RAMIFICATIONS
ON THE PLACEMENT OF HEAVY RAINFALL WHICH MAY BE CONFINED TO THE
EAST COAST OR COULD MIGRATE INLAND. WILL STAY IN THE MIDDLE WITH
THIS PREFERENCE AND REDUCE THE CONFIDENCE AS THE LATEST GUIDANCE
HAS NOT REDUCED THE MODEL UNCERTAINTY.


...MID-LEVEL ENERGY IMPACTING THE CENTRAL GREAT BASIN/UPPER
INTERMOUNTAIN WEST THROUGH SATURDAY...

FINAL PREFERENCE: GENERAL MODEL COMPROMISE
FORECAST CONFIDENCE: AVERAGE

ENERGY TRACKING UP AND OVER A WESTERN U.S. RIDGE WILL BE A FOCUS
FOR CONVECTION DURING THE NEXT FEW DAYS. THIS FEATURE IS WELL
REPRESENTED IN THE GUIDANCE WITH A POSITION IN THE VICINITY OF
EASTERN WA/NORTHERN ID BY 02/0000Z. SPREAD DOES GROW ALTHOUGH THE
SYSTEM ENDS UP LIFTING INTO SOUTHERN ALBERTA AT THAT POINT. THE
MODEL PREFERENCE WILL BE A GENERAL MODEL COMPROMISE TO ACCOUNT FOR
THE SMALLER-SCALE DIFFERENCES IN TIMING.


...SHORTWAVES OVER THE SOUTHWESTERN CONUS THIS WEEKEND...

FINAL PREFERENCE: A NON-12Z GFS MODEL BLEND
FORECAST CONFIDENCE: SLIGHTLY ABOVE AVERAGE

THE MODELS CONTINUE TO SHOW SOME SORT OF DISTURBANCE EVOLVING OUT
OF NORTHWESTERN MEXICO REACHING THE DESERT SOUTHWEST BY THE LATTER
PART OF THE WEEKEND. WITH THE EXCEPTION OF THE 12Z GFS...THE
MODELS SHOW THIS SYSTEM ACROSS THE SOUTHWESTERN STATES BY
04/0000Z. WPC WILL RECOMMEND A NON-12Z GFS SOLUTION GIVEN THE
SOMEWHAT OUTLYING NATURE OF ITS OUTPUT.


...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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