Prognostic Meteorological Discussion
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929
FXUS10 KWNH 011832
PMDHMD

MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
231 PM EDT SUN MAY 01 2016

VALID MAY 01/1200 UTC THRU MAY 05/0000 UTC

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

12Z MODEL EVALUATION...INCLUDING THE NAM/GFS/UKMET/CMC AND ECMWF

...FRONTAL ZONE AND SHORTWAVES EJECTING FROM THE SOUTHWEST/PLAINS
TOWARD THE EAST COAST...
...NORTHERN STREAM SHORTWAVE SETTLING INTO THE MEAN LONGWAVE
TROUGH BASE OVER THE PLAINS/SOUTHEAST...

PREFERENCE: 12Z ECMWF
CONFIDENCE: BELOW AVERAGE

THE FLOW OVER THE CENTRAL AND EASTERN U.S. IS MORE BROADLY
CHARACTERIZED BY A FLOW PATTERN TAKING SHORTWAVE IMPULSES OUT OF
THE SOUTHWEST AND THE PLAINS TOWARD THE EAST COAST. A MEAN
LONGWAVE TROUGH AXIS REMAINS ESTABLISHED OVER THE MS VALLEY
THROUGH TUES AS NORTHERN AND SOUTHERN STREAM WAVES CONVERGE
DOWNSTREAM OF A STRONG NORTHERN ROCKIES RIDGE. THE FIRST
NOTEWORTHY SHORTWAVE AND SURFACE LOW REFLECTION IS HANDLED
SIMILARLY BY MOST OF THE MODELS...TRACKING TOWARD THE MID ATLANTIC
BY MON AND THEN TOWARD THE COAST OF NEW ENGLAND MON NIGHT.
STRONGER MODEL CLUSTERING FAVORS THE 12Z UKMET/12Z CMC AND 12Z
ECMWF WITH THIS SYSTEM...AS THE 12Z NAM AND 12Z GFS BOTH APPEAR A
BIT TOO WEAK. A SECOND WAVE WILL DEVELOP ALONG THE ATTENDANT FRONT
OVER THE MID-ATLANTIC BY MON NIGHT/TUES IN RESPONSE TO A NORTHERN
STREAM TROUGH DIGGING ACROSS THE OH VALLEY. THE 12Z GFS IS MORE
PROGRESSIVE WITH THIS SHORTWAVE...AND ALONG WITH THE 12Z NAM...IT
WANTS TO SEND THIS WAVE OF LOW PRESSURE MORE PROGRESSIVELY UP OFF
SOUTHERN NEW ENGLAND BY TUES NIGHT. THE NON-NCEP MODELS ALL KEEP
THIS SECONDARY WAVE FOCUSED FARTHER SOUTH AND EVOLVING OVER THE
MID-ATLANTIC AS EVERY STRONGER HEIGHT FALLS ARRIVE DOWN ACROSS THE
GREAT LAKES. WILL LEAN TOWARD A NON-NCEP CONSENSUS LED BY THE 12Z
ECMWF FOR NOW.


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

PREFERENCE: NON-NAM CONSENSUS
CONFIDENCE: ABOVE AVERAGE

THE MODELS AGREE IN DEVELOPING A FULL-LATITUDE TROUGH OVER THE
EASTERN PACIFIC OCEAN...AND THIS WILL APPROACH THE WEST COAST ON
TUES. THE GUIDANCE IS IN RELATIVELY GOOD AGREEMENT AND HAS SHOWN
SOME STABILITY FROM RUN TO RUN. HOWEVER...THE 12Z NAM APPEARS TO
BE UNDER DOING THE AMOUNT OF ENERGY DIGGING INTO THE BASE OF THE
TROUGH BY THE END OF THE PERIOD AS THE GLOBAL MODELS ALL SUGGEST
SOMEWHAT STRONGER HEIGHT FALLS AND A CLOSED LOW DEVELOPMENT
OFFSHORE CENTRAL/NORTHERN CA. WILL PREFER A NON-NAM CONSENSUS AS A
RESULT.


...DEEP UPPER TROUGH/CLOSED LOW DEVELOPING OVER THE GREAT LAKES
TUES AND WED...
...SURFACE LOW PRESSURE DEEPENING ALONG THE MID-ATLANTIC COAST...

PREFERENCE: 12Z ECMWF
CONFIDENCE: AVERAGE

THE PATTERN TRENDS TOWARD A DEVELOPING OMEGA BLOCK THIS PERIOD
THAT WILL SPAN THE ENTIRE U.S. BY TUES AND WED. THIS WILL INCLUDE
A STRONG UPPER TROUGH AND DEVELOPING CLOSED LOW THAT WILL DIG AND
FEED INTO THE BROAD MEAN WEAKNESS/TROUGH OVER THE GREAT LAKES AND
EASTERN U.S. TUES AND WED. THE STRONGER HEIGHT FALLS WILL BE
CATCHING UP TO A BAROCLINIC ZONE OVER THE SOUTHEAST AND
MID-ATLANTIC STATES WHICH WILL ALLOW LOW PRESSURE ALREADY FOCUSED
OVER THE MID-ATLANTIC COASTAL PLAIN TO THEN DEEPEN RATHER
AGGRESSIVELY OFF THE DELMARVA BY LATE WED. THE 12Z GFS IS THE
MODEL MOST OUT OF TOLERANCE WITH THE MODEL CONSENSUS...AND WANTS
TO FOCUS MORE LOW PRESSURE FARTHER NORTH OVER THE LOWER GREAT
LAKES AND PORTIONS OF THE NORTHEAST. THE GFS IS ALSO THE STRONGEST
SOLUTION WITH ITS UPPER TROUGH OVER THE GREAT LAKES. THE MODEL
CONSENSUS MAINTAINS A MORE ORGANIZED AREA OF LOW PRESSURE FARTHER
SOUTH...ALTHOUGH THE 12Z NAM APPEARS TOO WEAK. THE NON-NCEP MODELS
SHOW BETTER CLUSTERING WITH THIS. THE 00Z UKMET WAS LOOKING TOO
STRONG OWING TO A STRONGER AND NEGATIVELY TILTED SHORTWAVE LIFTING
NORTH OUT OF THE BASE OF THE LARGER SCALE TROUGH ON WED ALONG THE
EAST COAST. THE OTHER GUIDANCE AGREES ON THIS SHORTWAVE BEING
THERE BUT WITH A SOMEWHAT WEAKER VERSION BY COMPARISON. THE 12Z
UKMET HAS TRENDED TOWARD THIS CONSENSUS. RIGHT NOW THE 12Z ECMWF
TENDS TO REPRESENT THE MODEL CONSENSUS THE BEST...AND AS A RESULT
WILL FAVOR THIS SOLUTION.


...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

$$





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