Prognostic Meteorological Discussion
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FXUS10 KWNH 230644
PMDHMD

MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
243 AM EDT WED AUG 23 2017

VALID AUG 23/0000 UTC THRU AUG 26/1200 UTC

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

...AN EVALUATION OF THE 00 UTC MODELS ALONG WITH
PREFERENCES/FORECAST CONFIDENCE...

...TROPICAL DISTURBANCE ASSOCIATED WITH THE REMNANTS OF HARVEY...

MODELS REMAIN IN GOOD AGREEMENT IN SHOWING HARVEY REDEVELOPING
INTO A TROPICAL SYSTEM AND THEN MOVING NORTHWESTWARD TOWARDS THE
TEXAS COAST. STILL SOME UNCERTAINTY WITH THE STRENGTH AND EXACT
TRACK OF THIS SYSTEM. A BLEND OF THE 00Z GFS/00Z ECMWF/00z GEFS
MEAN AND THE 18Z HURRICANE WRF AND NEW HMON TROPICAL CYCLONE MODEL
SHOULD WORK WELL DUE TO INCREASED CLUSTERING OF THESE SOLUTIONS.
THE 12Z UKMET/00Z NAM FORM THE RIGHT SIDE OF THE DISTRIBUTION AND
12Z ECMWF ENSEMBLE MEAN/00Z CANADIAN GLOBAL IS ON THE LEFT SIDE.
THESE LEFT/RIGHT BOOKENDS ARE CONSIDERED LOWER PROBABILITY
SOLUTIONS. SEE THE NATIONAL HURRICANE CENTER TROPICAL WEATHER
OUTLOOKS FOR INDICATIONS OF WHEN THE SYSTEM COULD REDEVELOP.

...COLD FRONT IN NEW ENGLAND AND CAROLINAS/GA...

PREFERENCE: NON-NAM MODEL CONSENSUS
FORECAST CONFIDENCE: ABOVE AVERAGE

OVERALL...THE MODELS REMAIN IN FAIRLY GOOD AGREEMENT WITH THE AND
COLD FRONT MOVING ACROSS THE NORTHEAST....WITH WAVES OF LOW
PRESSURE RIDING ALONG THE FRONT IN THE CAROLINAS.
THE 00Z NAM BECOMES AN OUTLIER IN DEVELOPING A STRONGER WAVE ALONG
THE FRONT IN EASTERN NORTH CAROLINA FOLLOWING A BOUT OF HEAVY
CONVECTIVE RAINFALL...WHICH ARTIFICIALLY LOWERS SURFACE PRESSURES.
 THE 00Z GFS/ECMWF/UKMET AGREE BETTER ON THE WAVE
LOCATION/TRACK...AND ARE PREFERRED.  A GENERAL MODEL BLEND SHOULD
SUFFICE FOR THE COLD FRONT AS IT CROSSES NEW ENGLAND WITH GOOD
CLUSTERING OF THE MODELS/ENSEMBLE MEANS.

...STRONG HEIGHT FALLS MOVING INTO PACIFIC NORTHWEST BY
THURSDAY...MID LEVEL TROUGH CROSSING THE NORTHERN PLAINS FRI...

PREFERENCE: BLEND OF 00Z GFS/ECMWF/UKMET
FORECAST CONFIDENCE: SLIGHTLY ABOVE AVERAGE

MODELS REMAIN IN PRETTY CLOSE AGREEMENT THE 500 MB TROUGH MOVING
ONSHORE IN THE PACIFIC NORTHWEST EARLY THU.  AS THE TROUGH MOVES
INLAND...SHORTWAVE ENERGY AT THE BASE OF THE TROUGH PRODUCES A
WAVE THAT CROSSES WY/MT ON THU AND MOVES INTO THE NORTHERN PLAINS
FRI.
THE 00Z NAM IS SLIGHTLY FASTER THAN THE 00Z GFS/12Z-00Z
ECMWF/UKMET...WHICH CLUSTER WELL.
THE 12Z-00Z CANADIAN GLOBAL REPRESENTS A LESS LIKELY
OUTCOME...BEING A DEEPER SOLUTION WITH THE TROUGH. GIVEN EXCELLENT
CLUSTERING AMONG THE GFS/UKMET/ECMWF AND EXCELLENT RUN TO RUN
CONTINUITY IN THE ECMWF...THIS GROUP OF MODELS IS RECOMMENDED.

...QUASI-STATIONARY UPPER LOW IN THE VICINITY OF CA/DESERT
SOUTHWEST...

PREFERENCE: MODEL CONSENSUS
FORECAST CONFIDENCE: ABOVE AVERAGE

A 700-500 MB TROUGH/LOW OFF THE SOUTHERN CA COAST WILL SINK SLOWLY
SOUTHEAST THE NEXT COUPLE OF DAYS. THE 00Z NAM/GFS/00Z ECMWF
CLUSTER WELL WITH THE AMPLITUDE/TIMING AND ARE PREFERRED.
AS THE MID LEVEL ANTICYCLONE STRENGTHENS...THE TROUGH BECOMES MORE
SHEARED ON DAY 3.

...MID LEVEL CIRCULATION FORECAST TO FORM NEAR FL EAST COAST...

PREFERENCE: GFS/ECMWF/UKMET MODEL CONSENSUS
FORECAST CONFIDENCE: SLIGHTLY ABOVE AVERAGE

THE MODELS INDICATE A BROAD 700 MB CIRCULATION FORMS IN A CYCLONIC
SHEAR AXIS CROSSING THE FL PENINSULA THU.  THE CIRCULATION DRIFTS
NORTHEAST THROUGH FRIDAY NIGHT.  THE 00Z NAM IS STRONGER AND A BIT
SLOWER THAN THE GFS/ECMWF/UKMET IN MOVING THE CIRCULATION. DUE TO
SUPPORT FROM THE SREF AND GEFS MEANS...THE OPERATIONAL
GFS/ECMWF/UKMET ARE PREFERRED.

www.wpc.ncep.noaa.gov/html/model2.shtml
www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml

PETERSEN

$$




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