Prognostic Meteorological Discussion
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FXUS10 KWNH 241659
PMDHMD

MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1259 PM EDT FRI APR 24 2015

VALID APR 24/1200 UTC THRU APR 28/0000 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 MONA
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 12Z NAM...12Z GFS...00Z ECMWF BLEND BUT MORE WEIGHT
            TOWARD THE NAM/GFS AFTER F060 HOURS
CONFIDENCE: SLIGHTLY ABOVE AVERAGE

THERE IS RELATIVELY SIMILAR HANDLING IN THE LATEST MODELS
REGARDING THE UPPER TROUGH AND CLOSED LOW EVOLUTION OVER THE FOUR
CORNERS REGION THROUGH ABOUT F060 HOURS...00Z/27. BEYOND 00Z/27 IS
WHEN MORE SIGNIFICANT DIFFERENCES SHOW UP REGARDING THE EJECTION
OF THE CLOSED MID-LEVEL LOW INTO TEXAS. THERE HAS BEEN MORE
CONVERGENCE IN THE ECMWF/GEFS/CMC ENSEMBLE MEMBERS OBSERVED OVER
THE PAST FEW CYCLES CENTERED ON 12Z/27 WITH MOST OF THE FASTER
ENSEMBLE MEMBERS SLOWING TOWARD A GROWING CONSENSUS NEAR THE
MIDDLE GROUND 00Z ECMWF MEAN. THE 700 MB LOW IN THE 00Z ECMWF IS
DISPLACED A BIT SOUTHEAST AND A BIT STRONGER COMPARED TO THE
REMAINING DETERMINISTIC/ENSEMBLE GUIDANCE...INCLUDING THE 00Z
ECMWF MEAN. THEREFORE WHILE A BLEND OF THE 12Z NAM...12Z GFS...00Z
ECMWF IS PREFERRED...MORE WEIGHT TOWARD THE NAM/GFS IS RECOMMENDED
AFTER 00Z/27.


SOUTHERN STREAM SHORTWAVE TRAVELING FROM THE SRN/CNTRL HIGH PLAINS
  TO THE MID-ATLANTIC THROUGH SUN
ASSOCIATED SURFACE PATTERN ALONG THE EAST COAST
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: BLEND OF THE 12Z NAM...12Z GFS...00Z ECMWF
CONFIDENCE: AVERAGE

SIMILAR IDEAS SHOWN IN THE NAM/GFS/ECMWF WHICH AGREE WITH THE
LATEST ENSEMBLE MEANS...BUT WITH THE ECMWF A BIT SLOWER AND GFS A
BIT FASTER BY SUN MORNING ACROSS THE APPALACHIANS WITH A SURFACE
LOW. TRENDS IN THE DETERMINISTIC GUIDANCE ARE MINIMAL...AND THE
ENSEMBLES SHOW CLUSTERING BETWEEN THE FASTER/SLOWER IDEAS.
THEREFORE...AN EVEN BLEND OF THE NAM/GFS/ECMWF ARE PREFERRED.


DEEP CLOSED LOW REMAINING ACROSS NEW ENGLAND AND THE EASTERN GREAT
LAKES
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: BLEND OF THE 12Z NAM...12Z GFS...00Z ECMWF
CONFIDENCE: AVERAGE

THERE ARE SEVERAL SMALL SCALE VORTICITY MAXIMA DEPICTED IN THE
GUIDANCE THAT WILL MOVE THROUGH THE WRN PORTION OF THIS LARGE
CLOSED LOW AS IT MEANDERS NEAR THE NEW ENGLAND COAST...WHICH ARE
DIFFICULT TO TRACK ON AN INDIVIDUAL BASIS. HOWEVER...LOOKING AT
THE BIGGER PICTURE...IT THE ENSEMBLE MEANS SHOW GOOD CLUSTERING
WITH HIGHER HEIGHTS THAN DEPICTED BY THE 00Z CMC ALONG THE WEST
SIDE OF THE CLOSED LOW...AND SEVERAL MORE INTENSE VORTICITY MAXIMA
ARE NOTED IN THE 00Z UKMET WHICH ARE NOT SUPPORTED IN THE
REMAINING DETERMINISTIC GUIDANCE AT THIS TIME. A BLEND OF THE
NAM/GFS/ECMWF APPEARS THE BEST ROUTE AT THIS TIME.


TROUGH/FRONT FOCUSED ACROSS THE NORTHERN HIGH PLAINS SUN AND MON
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: NON 12Z NAM BLEND
CONFIDENCE: ABOVE AVERAGE

OUTSIDE OF THE WEAKER/FLATTER NAM...THE MODELS SHOW SIMILAR WITH
THIS 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...

OTTO

$$





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