Prognostic Meteorological Discussion
Issued by NWS

Current Version | Previous Version | Text Only | Print | Product List | Glossary Off
Versions: 1 2 3 4

000
FXUS10 KWNH 301640
PMDHMD

MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1239 PM EDT SAT APR 30 2016

VALID APR 30/1200 UTC THRU MAY 04/0000 UTC

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

12Z MODEL EVALUATION...INCLUDING THE NAM AND GFS

...UPPER LOW EJECTING ACROSS THE CENTRAL PLAINS TODAY...
...ENERGY EJECTING/SHEARING ACROSS THE MIDWEST/NORTHEAST...
...SURFACE LOW MOVING FROM THE MID MS VALLEY TO THE NORTHEAST...

PREFERENCE: BLEND OF THE 12Z GFS/00Z UKMET AND 00Z ECMWF
CONFIDENCE: AVERAGE

THE UPPER LOW OVER THE CENTRAL PLAINS TODAY WILL WEAKEN AND SHEAR
OUT ACROSS THE MIDWEST...LOWER GREAT LAKES AND NORTHEAST THROUGH
SUN AND MON WHILE TENDING TO BE CAPTURED BY A WEAK NORTHERN STREAM
TROUGH DIGGING DOWN ACROSS THE GREAT LAKES. THIS WILL ALLOW
SURFACE LOW PRESSURE TO MOVE FROM THE LOWER MO VALLEY ACROSS THE
OH VALLEY ON SUN AND THEN INTO THE NORTHEAST ON MON. THE 12Z NAM
BECOMES A WEAKER OUTLIER WITH THIS SYSTEM...WITH THE 00Z CMC
LIKELY A LITTLE TOO DEEP. THE 12Z GFS/00Z UKMET AND 00Z ECMWF
CLUSTER IN BETWEEN CAMPS AND HAVE REASONABLY GOOD TIMING
AGREEMENT. THUS WILL PREFER THE LATTER CONSENSUS.


...UPPER LOW EVOLVING OVER THE SOUTHWEST/FOUR CORNERS...
...ENERGY EJECTING EAST ACROSS THE PLAINS...
...SHEARING INTO EAST BY TUES WITH POSSIBLE SURFACE WAVE...
...NORTHERN STREAM SHORTWAVE INTRUSION MON AND TUES...

PREFERENCE: BLEND OF THE 00Z UKMET/00Z ECMWF AND 00Z ECENS MEAN
CONFIDENCE: BELOW AVERAGE

THE GUIDANCE SHOWS GOOD AGREEMENT IN TAKING THE CURRENT CLOSED LOW
DIGGING THROUGH SOUTHERN NV FARTHER OFF TO THE SOUTHEAST AND THEN
THROUGH THE FOUR CORNERS REGION ON SUN. AT LEAST A PORTION OF THIS
ENERGY WILL EJECT EAST ACROSS THE CENTRAL PLAINS SUN NIGHT AND
MON...BEFORE THEN SHEARING INTO THE EASTERN U.S. ON TUES. THIS
ENERGY WILL ATTEMPT TO INVIGORATE A WAVE OF LOW PRESSURE ALONG A
FRONTAL ZONE THAT WILL BE DRAPING FROM NEAR THE MID-ATLANTIC BACK
TO THE SOUTHWEST DOWN TOWARD THE WESTERN GULF COAST. THE EVOLUTION
OF THIS WILL BE COMPLICATED BY THE INTRUSION OF NORTHERN STREAM
SHORTWAVE ENERGY COMING DOWN THE EAST SIDE OF A STRONG BLOCKING
RIDGE OVER THE NORTHERN HIGH PLAINS AND SOUTHWEST CANADA. THE 12Z
GFS APPEARS TOO PROGRESSIVE WITH THE INTERACTION OF THE TWO
SHORTWAVE SYSTEMS...WHICH RESULTS IN A FASTER WAVE PROPAGATION
INTO THE MID-ATLANTIC REGION ON TUES AND ALSO A MORE SUPPRESSED
FRONTAL ZONE ACROSS THE GULF COASTS AND THE SOUTHEAST BY TUES
NIGHT. THE 12Z NAM SUGGESTS A SLOWER/STRONGER EJECTION OF THE
ENERGY ACROSS THE PLAINS AND INTO THE EAST BUT WITH LESS
INTERACTION WITH THE NORTHERN STREAM ENERGY. THE NAM IS LIKELY TOO
FAR NORTH WITH ITS SURFACE WAVE/FRONT ACROSS THE EAST...AND HAS
TOO MUCH ENERGY TOO FAR WEST BACK OVER THE HIGH PLAINS ON TUES.
THE 00Z CMC/00Z UKMET AND 00Z ECMWF SPLIT THE DIFFERENCE AND SHOW
ONLY PARTIAL INTERACTION BETWEEN THE NORTHERN STREAM ENERGY AND
EJECTING CLOSED LOW ENERGY. STRONGER MODEL CLUSTERING FAVORS A
BLEND OF THE UKMET AND ECMWF WHICH WOULD ALLOW FOR A PORTION OF
THE CLOSED LOW ENERGY TO SHEAR INTO THE MID-ATLANTIC BY TUES WITH
A CLOSED LOW/TROUGH HANGING BACK OVER THE CENTRAL PLAINS OR MID MS
VALLEY. THE 00Z ECENS MEAN TENDS TO FAVOR THIS...AND THUS A BLEND
OF THE 00Z UKMET/00Z ECMWF AND 00Z ECENS MEAN WILL BE PREFERRED
WITH LIMITED CONFIDENCE.


...DEEP UPPER TROUGH APPROACHING THE WEST COAST ON TUES...

PREFERENCE: BLEND OF THE 12Z GFS AND 00Z ECMWF
CONFIDENCE: SLIGHTLY ABOVE AVERAGE

THE MODELS AGREE IN DEVELOPING A FULL-LATITUDE TROUGH OVER THE
EASTERN PACIFIC OCEAN WHICH WILL APPROACH THE WEST COAST ON TUES.
THE GUIDANCE IS IN RELATIVELY GOOD AGREEMENT WITH THE LARGER SCALE
MASS FIELD DETAILS. ALTHOUGH THE 12Z NAM AND 00Z UKMET BOTH APPEAR
TO BE A BIT TOO SHARP WITH THEIR RESPECTIVE TROUGHS BY THE END OF
THE PERIOD. THE 12Z GFS AND 00Z ECMWF BOTH TEND TO CLUSTER
TOGETHER A BIT BETTER AND HAVE REASONABLY STRONG SUPPORT FROM THE
GEFS MEAN AND ECENS MEAN...SO A BLEND OF THE GFS AND ECMWF WILL BE
PREFERRED WITH THIS NEXT SYSTEM.


...MODEL TREND GRAPHICS AT
www.wpc.ncep.noaa.gov/html/model2.shtml...

...500 MB FORECASTS AT
www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml...

ORRISON

$$





USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.