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FXUS10 KWNH 251653
PMDHMD

MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1253 PM EDT SAT APR 25 2015

VALID APR 25/1200 UTC THRU APR 29/0000 UTC

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

12Z NAM/GFS EVALUATION...INCLUDING PRELIMINARY PREFERENCES
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

DEEP TROUGH/CLOSED LOW DIGGING INTO SOUTHWEST U.S. THIS WEEKEND
LOW PRESSURE DEVELOPING OVER THE SOUTHERN PLAINS BY MON
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: BLEND OF THE 12Z NAM...00Z ECMWF...00Z UKMET
CONFIDENCE: SLIGHTLY ABOVE AVERAGE

REGARDING THE 700 MB REFLECTION THAT MOVES INTO THE SRN PLAINS
MONDAY MORNING...THE 12Z GFS IS NORTH OF THE LATEST
DETERMINISTIC/ENSEMBLE CONSENSUS... AND THE 12Z GFS LIKELY HAS
CONVECTIVE FEEDBACK OVER SERN TX ON MON. THE 00Z ECMWF/UKMET ARE
SLIGHTLY SOUTH OF THE CONSENSUS...WITH THE NAM NEAR THE MIDDLE TO
JUST NORTH OF THE CONSENSUS. GIVEN WOBBLES ARE LIKELY WITH FUTURE
RUNS...THIS AGREEMENT IS PRETTY GOOD BUT IT SEEMS CLEAR TO RULE
OUT THE 12Z GFS...IN FAVOR OF THE 12Z NAM...00Z ECMWF AND 00Z
UKMET GIVEN THEIR BLENDED PLACEMENT CLOSE TO THE AGREEABLE
ENSEMBLE MEANS 700-500 MB HEIGHT CENTROID THROUGH TUE. THIS MODEL
AGREEMENT IS ALSO TRUE REGARDING LIKELY SURFACE LOW DEVELOPMENT
NEAR THE CNTRL GULF COAST


SOUTHERN STREAM TROUGH TRAVELING FROM THE MISS VALLEY TO THE
  MID-ATLANTIC THROUGH TONIGHT
ASSOCIATED SURFACE LOW CROSSING THE REGION
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL COMPROMISE
CONFIDENCE: ABOVE AVERAGE

THERE ARE MINOR DETAIL DIFFERENCES REMAINING IN THE LATEST
GUIDANCE...BUT IT SHOULD BE NOTED THAT THERE HAS BEEN A STRONG
TREND IN THE LATEST ENSEMBLE GUIDANCE FOR A WEAKER REMNANT SURFACE
LOW NEAR THE SRN APPALACHIANS SUN MORNING. THEREFORE...MODELS LIKE
THE 00Z UKMET...WHICH HOLD ONTO A SURFACE LOW LONGER THAN THE
CURRENT CONSENSUS...SHOULD BE GIVEN LESS EMPHASIS.


DEEP CLOSED LOW REMAINING ACROSS NEW ENGLAND
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: NON 00Z CMC BLEND
CONFIDENCE: SLIGHTLY ABOVE AVERAGE

OUTSIDE OF THE 00Z CMC...WHICH IS SLOWER MON NIGHT WITH A
SHORTWAVE PINWHEELING AROUND THE SLOWLY DEPARTING CLOSED LOW
CENTERED OFF OF NEW ENGLAND...THE MODELS SHOW REASONABLE AGREEMENT
HERE. DETAIL DIFFERENCES WITH INDIVIDUAL SHORTWAVES ARE BEST
BLENDED WITH A NON 00Z CMC MODEL CONSENSUS.


TROUGH/FRONT CROSSING THE NORTHERN PLAINS THROUGH MON
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: BLEND OF THE 12Z GFS AND 00Z ECMWF
CONFIDENCE: AVERAGE

BLENDING THE GFS/ECMWF REPRESENTS THE MIDDLE OF THE LATEST MODEL
SPREAD...FALLING CLOSE IN LINE WITH THE ENSEMBLE MEANS. THE 12Z
NAM APPEARS FLATTEST/WEAKEST ALOFT WITH THIS FEATURE.


TROUGH/FRONT APPROACHING THE PACIFIC NORTHWEST BY TUE MORNING
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: NON 00Z UKMET BLEND
CONFIDENCE: AVERAGE

THE 00Z UKMET IS SIGNIFICANTLY SLOWER WITH A SHORTWAVE APPROACHING
THE PACIFIC NORTHWEST EARLY ON TUE...WHILE THE REMAINING
DETERMINISTIC MODELS AND ENSEMBLE MEANS ARE FASTER WITH REASONABLE
AGREEMENT.


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

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

OTTO

$$





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