Prognostic Meteorological Discussion
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FXUS10 KWNH 271702
PMDHMD

MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1200 PM EST MON FEB 27 2017

VALID FEB 27/1200 UTC THRU MAR 03/0000 UTC

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

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

...BROAD LONGWAVE TROUGH OVER THE WEST DAY 1...
...CONFLUENCE OF THREE SHORTWAVES OVER THE PLAINS LATE TUE-WED...
...FEATURE AND ASSOCIATED SFC LOW EJECTING EAST ACROSS THE GREAT
LAKES/NORTHEAST LATE WED/EARLY THU...
...TRAILING COLD FRONT CROSSING THE MS RIVER VALLEY WED AND
THROUGH THE MID-ATLANTIC/SOUTHEAST BY LATE WED...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 12Z NAM/GFS
CONFIDENCE: SLIGHTLY ABOVE AVERAGE

MID TO LATE MORNING WV/IR IMAGERY DEPICTS FIRST IN A SERIES OF
UPPER DISTURBANCES DROPPING ACROSS THE CENTRAL GREAT BASIN. GOOD
MODEL AGREEMENT EXISTS WITH THE SHEARING LEAD SHORTWAVE...WITH
THIS FEATURE EXPECTED TO CROSS THE NORTHERN/CENTRAL ROCKIES
THROUGH LATE TONIGHT BEFORE SHIFTING TOWARD THE UPPER MIDWEST
EARLY WEDNESDAY. MODELS STILL STRUGGLING A BIT WITH DETAILS FROM
THERE...BUT CAN AGREE THAT THERE WILL BE SOME DEGREE OF PHASING
WITH THE LINGERING SHORTWAVE ENERGY OFF COMING ASHORE THE FAR S
CA/BAJA COAST THIS MORNING. AT THIS TIME...EXPECT THE SOUTHERN
FEATURE TO SLIDE ACROSS THE DESERT SOUTHWEST ON TUE...BEFORE IT
ROUNDS THE BASE OF THE MERIDIONALLY EXPANDING LONGWAVE TROUGH AND
PHASES WITH THE PARENT TROUGH OVER THE PLAINS AS IT TRANSLATES
EAST. A THIRD PIECE OF SHORTWAVE ENERGY CURRENTLY LAGGING ACROSS
THE COAST OF BRITISH COLUMBIA THIS MORNING WILL DROP ACROSS THE
PAC NW TONIGHT...EVENTUALLY CROSSING THE NORTHERN GREAT
BASIN/NORTHERN PLAINS TUESDAY INTO WED. THIS WAVE TOO WILL GET
INCORPORATED IN THE MEAN WAVE.

IN THE NEAR TERM...GOOD AGREEMENT WITH LEAD WAVE CROSSING THE
NORTHERN/CENTRAL HIGH PLAINS TONIGHT....WITH RESULTANT BROAD SWLY
FLOW TO SPUR LEE CYCLOGENESIS...IN THE FORM OF A PAIR OF SURFACE
WAVES DEVELOPING ALONG THE MID-LEVEL BAROCLINIC ZONE FROM THE
MID-MISSOURI VALLEY BACK INTO THE CENTRAL HIGH PLAINS TUESDAY. THE
SURFACE LOWS WILL SHIFT NE INTO THE GREAT LAKES W/THE LEADING
WAVE/HEIGHT FALLS WITH SURFACE FRONT EXTENDING BACK TO THE
SOUTHERN HIGH PLAINS IN ANTICIPATION OF THE EJECTION OF THE MEAN
WAVE AS IT SWINGS NEUTRAL INTO THE PLAINS EARLY WED.

PROBLEMS ARISE FOR THE MIDWEEK PERIOD...WITH MODELS STILL
STRUGGLING TO SOME DEGREE IN DIAGNOSING THE TIMING OF THE EJECTING
UPPER TROUGH...WITH RESULTANT IMPACTS ON FRONTAL TIMING FOR
WED-EARLY THU OVER THE EASTERN-THIRD OF THE CONUS IN THE DAY 2/3
PERIOD. THE 12Z GFS HAS TRENDED DEEPER AND SLIGHTLY SLOWER WITH
THE UPPER FEATURE...WITH THE EFFECT OF SLOWING DOWN THE SURFACE
WAVE TOWARD THE TIMING OF THE REST OF AVAILABLE GUIDANCE WED/THU.
12Z/GFS REMAINS THE FASTEST/MOST AGGRESSIVE WITH THE SOUTHERN
SHORTWAVE FROM THE CENTRAL PLAINS TO THE OHIO VALLEY ON
WEDNESDAY/WEDNESDAY NIGHT...BUT TEMPORAL DIFFERENCES ARE NARROWING.

THE 00Z ECMWF TRENDED TOWARD THE FASTER GFS SOLUTION. THE 00Z CMC
IS IN GOOD AGREEMENT OVERALL WITH THE ECMWF SOLUTION AND IS A BIT
QUICKER WITH THE TRAILING COLD FRONT...ESPECIALLY DAY 2 AND 3.
EXAMINING THE TREND OF THE PAST TWO SUCCESSIVE RUNS OF THE ECMWF
TOWARD THE FASTER SOLUTION...AND WITH THE 06Z NAEFS ONCE AGAIN
TRENDING FASTER...PREFERENCE IS CLEARLY TOWARD THE MORE
PROGRESSIVE SOLUTION WITH STRONG/FAST SW FLOW ALOFT.
ACCORDINGLY...WILL SHIFT PREFERENCE TOWARD THE 12Z GFS...AND WILL
MIX IN SOME 12Z NAM TO SLOW THE BLEND DOWN A BIT FURTHER TOWARD
THE REST OF THE GUIDANCE ENVELOPE PENDING THE ARRIVAL OF THE REST
OF THE 12Z SUITE. INCREMENTALLY BETTER HANDLING OF PATTERN
RECOGNITION BY MODELS DOES LEND TO AN UPTICK IN FORECAST
CONFIDENCE TO SLIGHTLY ABOVE AVERAGE.


...LOW AMPLITUDE SHORTWAVE CLIPPING THE NRN ROCKIES WED MORNING
INTO NORTHERN PLAINS/UPPER MIDWEST BY THU...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL BLEND
CONFIDENCE: AVERAGE

A DEEP UPPER LEVEL LOW CRASHES INTO THE AK PANHANDLE/NW BC LATE
TUESDAY...WITH SOME DAMPENING SHORTWAVE ENERGY EJECTING DOWNSTREAM
AS A LOW AMPLITUDE WAVE THAT CLIPS THE NORTHERN ROCKIES/NW
MT...BEFORE DROPPING ACROSS THE DAKOTAS INTO THE UPPER MIDWEST
THURSDAY AND THURSDAY AFTERNOON. THE 12Z GFS IS 6-12 HOURS SLOWER
IN TIMING WITH THIS FEATURE FOR THE END OF THE PERIOD. THE 00Z
CMC/ECMWF AND UKMET EACH SLOWED SLIGHTLY AS WELL...WITH THE
RESPECTIVE MODEL SOLUTIONS BLENDING TOGETHER WELL WITH THE 12Z
NCEP MODEL GUIDANCE...WITH RELATIVELY MINOR ISSUES. THE 12Z NAM
FEATURES SIMILAR TIMING BUT IS A BIT DEEPER WITH THE WAVE THAN THE
REST OF GUIDANCE. GIVEN TREND TOWARD CONSOLIDATING
SOLUTIONS...WILL FAVOR BLENDED MODEL SOLUTION TO SMOOTH TEMPORAL
DIFFERENCES AT THIS TIME AT AVERAGE CONFIDENCE.

www.wpc.ncep.noaa.gov/html/model2.shtml...

www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml...

MONTEFUSCO


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