Prognostic Meteorological Discussion
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000
FXUS10 KWNH 301855
PMDHMD

MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
254 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 MODEL GUIDANCE ALONG WITH FINAL
PREFERENCES/FORECAST CONFIDENCE...


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

FINAL PREFERENCE: GENERAL 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. HOWEVER...IT HAS MADE POSITIVE
ADJUSTMENTS TO THE EAST IN ITS MOST RECENT RUN. 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. WHILE THERE ARE DIFFERENCES EVIDENT IN THE RESULTANT
TROUGH POSITION...A GENERAL COMPROMISE OF THE AVAILABLE MODELS
APPEARS REASONABLE HERE.


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

FINAL 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...

FINAL PREFERENCE: GENERAL 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 WITH THE FEATURE MOVING INLAND DURING THE NEXT 6 TO 12
HOURS. THE 12Z CMC MOVED INTO BETTER AGREEMENT WITH OTHER
SOLUTIONS SO A GENERAL MODEL COMPROMISE IS WARRANTED.


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

FINAL PREFERENCE: 00Z ECMWF ENSEMBLE MEAN
FORECAST CONFIDENCE: 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. THERE
CONTINUES TO BE QUITE A BIT OF SPREAD AS MANY 12Z SOLUTIONS HAVE
TRENDED QUICKER...INCLUDING THE CMC/ECMWF. NOW THE 12Z GFS/GEFS
MEAN IS ON THE SLOWER SIDE AND FEEL IT WOULD BE BEST TO SPLIT THE
DIFFERENCE BETWEEN THE QUICKER 12Z SOLUTIONS AND THE PREVIOUS
PREFERENCE. THE 00Z ECMWF ENSEMBLE MEAN OFFERS A DECENT MIDDLE
GROUND WITH FORECASTER CONFIDENCE DECREASING AS A WHOLE.

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

FINAL 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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