Prognostic Meteorological Discussion
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FXUS10 KWNH 180638
PMDHMD

MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
137 AM EST WED JAN 18 2017

VALID JAN 18/0000 UTC THRU JAN 21/1200 UTC

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

...AN EVALUATION OF THE 00Z MODEL ALONG WITH FINAL
PREFERENCES/FORECAST CONFIDENCE...

...SHORT WAVE MOVING ACROSS THE MID ATLANTIC WED...
...SURFACE LOW FORMING OFF THE LONG ISLAND NY COAST WED...

PREFERENCE: A GENERAL MODEL BLEND
FORECAST CONFIDENCE: ABOVE AVERAGE

A SHORT WAVE OVER IL/IN EARLY WED TRACKS ACROSS THE OH
VALLEY...REACHING THE MID ATLANTIC COAST BY 18/18Z. BOTH THE 00Z
NAM AND GFS WERE VERY CLOSE WITH THE TRACK AND STRENGTH OF THE
SHORT WAVE... AND CLUSTERED WELL WITH THE MODEL CONSENSUS/ENSEMBLE
SOLUTIONS. BOTH SOLUTIONS WERE ALSO CLOSE WITH THE DEVELOPMENT OF
A SURFACE LOW FORMING OFF THE EASTERN TIP OF LONG ISLAND NY TOWARD
18/12Z...AND REMAIN CLOSE AS IT TRACKS EASTWARD.

THE 00Z UKMET/CMC/ECMWF WERE ALSO CLOSE WITH CLOSED MID LEVEL
LOW...THOUGH THE 00Z UKMET WAS A TAD FASTER WITH THE SURFACE LOW.
HOWEVER...IT WAS NOT SO FAST THAT IT CANNOT BE INCLUDED IN THE
GENERAL BLEND.


...CLOSED MID LEVEL LOW OVER THE NM TRACKING TO THE UPPER MS
VALLEY/GREAT LAKES FRI...
...WEAK SURFACE WAVE MOVING ACROSS THE ACROSS THE MIDDLE MS VALLEY
FRI...

PREFERENCE: NON-00Z CMC BLEND
FORECAST CONFIDENCE: AVERAGE

THE CLOSED MID LEVEL LOW OVER NM EARLY WED BROADENS AS IT TRACKS
ACROSS THE CENTRAL PLAINS THU BEFORE ELONGATING INTO A NEGATIVELY
TILTED TROUGH OVER THE UPPER GREAT LAKES FRI. THE 00Z NAM WAS
CLOSE TO THE MODEL CONSENSUS THROUGH DAY 2 ACROSS THE CENTRAL
PLAINS...BUT BECOMES FASTER THAN THE CONSENSUS AS THE CLOSED LOW
ELONGATES INTO A NEGATIVELY TILTED LONG WAVE TROUGH OVER THE GREAT
LAKES DURING FRI.

THE 00Z GFS WAS CLOSER TO THE MODEL CONSENSUS AS THE SYSTEM OPENS
UP AND BECOMES NEGATIVE. THE 00Z ECMWF WAS A BIT FASTER WITH THE
CLOSED MID LEVEL SYSTEM (AND IT HAS BEEN SPEEDING UP OVER THE PAST
THREE MODEL CYCLES). THE 00Z CMC HAS SLOWED ITS APPROACH WITH THE
CLOSED LOW...AND SUBSEQUENTLY WAS DROPPED FROM THE PREFERENCE. THE
FASTER 00Z ECMWF AND SLOWER 00Z CMC SUGGEST THAT THE FORECAST
CONFIDENCE HAS DROPPED TO ONLY AVERAGE.


...SHORT WAVES IN A FAST FLOW ACROSS THE PACIFIC NORTHWEST EARLY
WED...
...LONG WAVE TROUGH DIGGING INTO THE SOUTHWEST US THU...
...CLOSING MID LEVEL LOW OVER THE CENTRAL PLAINS BY EARLY SAT...

PREFERENCE: 00Z ECMWF/00Z GFS/00Z UKMET
FORECAST CONFIDENCE: AVERAGE

SHORT WAVE ENERGY IN THE FAST MID LEVEL FLOW CROSSES THE PACIFIC
NORTHWEST EARLY WED. DESPITE THE FAST FLOW...THERE WAS GENERALLY
GOOD MODEL AGREEMENT WITH THE TIMING...WITH BOTH THE 00Z NAM AND
00Z GFS CLOSE TO THE BEST CLUSTERING.

SHORT WAVE ENERGY DIVES INTO THE LONG WAVE TROUGH FORMING JUST OFF
THE WEST COAST THU...WHICH THEN CROSSES THE FOUR CORNERS REGION
FRI...BEFORE CLOSING OFF IN THE MID LEVEL OVER THE CENTRAL PLAINS
SAT. ONCE AGAIN...THE 00Z NAM WAS A BIT FASTER WITH THE LONG WAVE
TRACKING ACROSS THE SOUTHWEST...AND REMAINS FAST AS AN OPEN WAVE
CROSSING THE CENTRAL PLAINS EARLY SAT.

BY CONTRAST...THE 00Z GFS REMAINED CLOSE TO THE MODEL CONSENSUS
THROUGH SAT ACROSS THE CENTRAL PLAINS (JUST AHEAD OF THE SLIGHTLY
SLOWER 00Z GEFS MEAN). THE 00Z UKMET REMAINED CLOSE TO THE
CONSENSUS...BUT THE 00Z CMC HAS SLOWED WITH ITS SOLUTION. BECAUSE
OF THIS...IT WAS DROPPED FROM THE PREFERENCE.

IT SHOULD BE NOTED THAT THE BULK OF THE GUIDANCE HAS BEEN FASTER
WITH THIS SYSTEM...ESPECIALLY IN THE FRI INTO EARLY SAT RANGE...AS
THE MID LEVEL SYSTEM CLOSES OFF.


...STRONG CLOSED MID LEVEL SYSTEM APPROACHES THE WEST COAST FRI...
...OPENS INTO A NEGATIVELY TILTED TROUGH JUST OFF THE PACIFIC
NORTHWEST COAST SAT...

PREFERENCE: GENERAL MODEL COMPROMISE
FORECAST CONFIDENCE: SLIGHTLY ABOVE AVERAGE

A STRONG SHORT WAVE NEAR 42N 165W EARLY WED CLOSES OFF IN THE MID
LEVELS THU INTO FRI...BEFORE OPENING INTO A NEGATIVELY TILTED LONG
WAVE TROUGH JUST OFF THE PACIFIC NORTHWEST COAST EARLY SAT. BOTH
THE 00Z NAM AND 00Z GFS REMAINED CLOSE TO THE MODEL CONSENSUS
THROUGH EARLY SAT. WHILE THERE WAS GENERALLY GOOD AGREEMENT WITH
THE PLACEMENT OF THE SURFACE LOW THAT ACCOMPANIES THE MID LEVEL
SYSTEM...THERE ARE SOME DIFFERENCES IN LOW STRENGTH...SO FOR NOW A
GENERAL MODEL BLEND WAS FOLLOWED.

THE 00Z UKMET/CMC WERE CLOSE TO THEIR PREVIOUS SOLUTIONS...AND THE
00Z ECMWF WAS A BIT SLOWER WITH THE LONG WAVE TROUGH. IT WAS NOTED
THAT ALMOST ALL GUIDANCE HAS SHOWN A SLOWING TREND WITH THE MID
LEVEL SYSTEM...AND THIS TREND COULD CONTINUE INTO THE NEXT MODEL
CYCLE.


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

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

HAYES

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