Prognostic Meteorological Discussion
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FXUS10 KWNH 301725
PMDHMD

MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
124 PM EDT FRI SEP 30 2016

VALID SEP 30/1200 UTC THRU OCT 04/0000 UTC

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

...AN EVALUATION OF THE 12Z NAM/GFS ALONG WITH PRELIMINARY
PREFERENCES/FORECAST CONFIDENCE...


...PERSISTENT UPPER LOW SPINNING ACROSS THE OH VALLEY/GREAT LAKES
REGION...

PRELIMINARY PREFERENCE: NON-00Z CMC MODEL COMPROMISE
FORECAST CONFIDENCE: AVERAGE

WATER VAPOR IMAGERY AND 500-MB HEIGHT FIELDS SHOWED THE CONTINUED
PRESENCE OF A CLOSED LOW SITTING OVER THE OH VALLEY. THIS SYSTEM
REMAINS A FOCUS FOR AREAS OF MODERATE/HEAVY RAINFALL WITHIN THE
COMMA-HEAD AS WELL AS ALONG AN ENHANCED MOISTURE CHANNEL ALONG THE
EASTERN SEABOARD. MODELS CONTINUE TO SHOW THIS CIRCULATION LIFTING
NORTHWARD REACHING THE LOWER GREAT LAKES BY 02/1200Z. DURING THIS
PERIOD...THE 00Z CMC IS SLIGHTLY DISPLACED TO THE SOUTHWEST
COMPARED TO THE BETTER CLUSTERING. THIS SLOW-MOVING UPPER LOW
SHOULD EVENTUALLY MIGRATE EASTWARD TOWARD NEW ENGLAND AS IT FEELS
THE EFFECTS OF AN UPPER TROUGH DIPPING THROUGH EASTERN CANADA.
THERE ARE SOME DIFFERENCE WITH THE EVENTUAL POSITION OF THE UPPER
TROUGH EARLY NEXT WEEK BUT A NON-00Z CMC SOLUTION APPEARS TO BE
THE WAY TO GO.


...SHORTWAVE SHEARING ACROSS THE NORTHERN PLAINS EARLY IN THE
PERIOD...

PRELIMINARY PREFERENCE: GENERAL MODEL COMPROMISE
FORECAST CONFIDENCE: ABOVE AVERAGE

A SHORTWAVE WHICH CONTINUES TO SHEAR/DECAY ACROSS THE NORTHERN
ROCKIES WILL EVENTUALLY SPLIT WHILE CROSSING INTO THE ADJACENT
GREAT PLAINS. THE GUIDANCE APPEAR SIMILAR ACROSS THE BOARD WHICH
SUPPORTS A GENERAL MODEL COMPROMISE.


...INITIAL SHORTWAVE SWINGING THROUGH THE UPPER INTERMOUNTAIN WEST
ON SATURDAY...

PRELIMINARY PREFERENCE: NON-00Z CMC MODEL CONSENSUS
FORECAST CONFIDENCE: SLIGHTLY ABOVE AVERAGE

AMPLIFIED FLOW ACROSS THE EASTERN PACIFIC WILL MAINTAIN AN ACTIVE
PATTERN OVER THE WESTERN U.S. FOR THE NEXT FEW DAYS. FIRST...THE
INITIAL SHORTWAVE IS CURRENTLY SPINNING OFF THE PACIFIC NORTHWEST
COAST. THE 00Z CMC IS A BIT SLOWER AS THE SYSTEM LIFTS ACROSS THE
BRITISH COLUMBIA/ALBERTA BORDER. AS A RESULT...WILL FAVOR A
NON-00Z CMC MODEL CONSENSUS.


...MORE SIGNIFICANT UPPER TROUGH AFFECTING THE WEST COAST LATE IN
THE WEEKEND...
...EVENTUAL CLOSED LOW/ASSOCIATED FRONTAL ZONE MOVING TOWARD THE
FOUR CORNERS REGION...

PRELIMINARY PREFERENCE: BLEND OF THE 12Z GFS/06Z GEFS MEAN
FORECAST CONFIDENCE: SLIGHTLY BELOW AVERAGE

ON THE HEELS OF THE INITIAL SHORTWAVE MOVING INTO THE PACIFIC
NORTHWEST...A SEPARATE CLOSED LOW DROPS DOWN ALONG THE WEST COAST
BEFORE MOVING INLAND OVER NORTHWESTERN CA BY 02/1200Z. BY SUNDAY
EVENING...THERE IS SOME FORECAST SPREAD WITH THE 00Z UKMET ON THE
QUICKER END WHILE THE 00Z CMC REMAINS TO THE WEST AS IT SEEMS TO
BE WITH MOST SYSTEMS ON THE MAP. ENSEMBLE SPAGHETTI PLOTS SHOW A
DISPARITY BETWEEN THE GFS/ECMWF CAMPS WITH THE ECMWF ENSEMBLE
SOLUTIONS BEING SOMEWHAT QUICKER. WILL STICK TOWARD THE SLOWER
GROUP GIVEN THE TYPICAL BIAS OF MODELS BEING TOO QUICK EJECTING
CLOSED UPPER LOWS. WPC WILL PLAY A SPLIT BETWEEN THE 12Z GFS/06Z
GEFS MEAN.

...MID-LEVEL WEAKNESS ACROSS THE NORTHERN GULF OF MX BY MONDAY...

PRELIMINARY PREFERENCE: 12Z GFS
FORECAST CONFIDENCE: AVERAGE

WELL IN ADVANCE OF HURRICANE MATTHEW WILL BE AN ELONGATED AREA OF
LOWER HEIGHTS ACROSS THE GULF OF MX. GIVEN THE NATIONAL HURRICANE
CENTER FORECAST HAS BEEN CLOSER TO THE GFS SOLUTION...WILL LEAN IN
THAT DIRECTION GIVEN ITS SYNOPTIC INFLUENCE ON STEERING THIS
TROPICAL CYCLONE NORTHWARD.



...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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