Prognostic Meteorological Discussion
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FXUS10 KWNH 251845
PMDHMD

MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
245 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 MODEL EVALUATION...INCLUDING FINAL 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...12Z ECMWF...12Z 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 12Z ECMWF ADJUSTED
SLIGHTLY NORTH FROM ITS 00Z RUN AND THE 12Z UKMET REMAINS SIMILAR
TO ITS PREVIOUS RUN...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/ECMWF/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

THE MODELS SHOW SIMILARLY WITH THE SYNOPTIC SCALE DETAILS OF THIS
SYSTEM WITH THE LATEST 12Z DETERMINISTIC MODELS COMING INTO
AGREEMENT ON A WEAKER REMNANT SURFACE LOW NEAR THE SRN
APPALACHIANS SUN MORNING AS SEEN WITH THE LATEST ENSEMBLE
GUIDANCE.


DEEP CLOSED LOW REMAINING ACROSS NEW ENGLAND
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: NON 12Z CMC BLEND
CONFIDENCE: SLIGHTLY ABOVE AVERAGE

OUTSIDE OF THE 12Z 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 12Z CMC MODEL CONSENSUS.


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

THE 12Z 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. THE 12Z ECMWF HAS BEEN WOBBLING ABOUT A SIMILAR TIMING
OVER ITS PAST 4 RUNS...WITH THE MOST RECENT 12Z ECMWF TRENDING A
BIT SLOWER...BUT NOT TO THE EXTENT OF THE UKMET.


...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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