999
FXUS10 KWNH 201644
PMDHMD
MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1243 PM EDT MON APR 20 2020
VALID APR 20/1200 UTC THRU APR 24/0000 UTC
...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR
INGEST...
12Z MODEL EVALUATION WITH INITIAL PREFERENCES AND CONFIDENCE
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
SURFACE LOW TRACKING OFF THE MID ATLANTIC COAST TODAY
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: NON-CMC BLEND
CONFIDENCE: MODERATE-HIGH
SHORTWAVE TROUGH NOW EXITING THE COAST WITH A DUAL-LOW SURFACE
STRUCTURE WILL CONTINUE TO INTENSIFY OFFSHORE AS IT CONSOLIDATES
INTO ONE MAIN SURFACE LOW WELL TO THE SOUTHEAST OF NEW ENGLAND.
THE MAIN DIFFERENCE NOTED IN THE MODELS IS A SLOWER PROGRESSION
WITH THE 00Z CMC, BUT OTHERWISE A MULTI-DETERMINISTIC MODEL BLEND
SHOULD SUFFICE.
DEVELOPING LONG WAVE TROUGH OVER NEW ENGLAND WITH SURFACE LOW
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 12Z GFS/00Z ECMWF/00Z UKMET BLEND
CONFIDENCE: MODERATE-HIGH
SHORT WAVE ENERGY DIVING OUT OF CENTRAL CANADA IN THE FAST MID
LEVEL FLOW DROPS TO THE BASE OF A DEVELOPING LONG WAVE TROUGH OVER
THE UPPER GREAT LAKES BY TUESDAY MORNING, AND THEN THE LONG WAVE
TROUGH TAKES ON A NEGATIVE TILT. THIS WILL SUPPORT A PRIMARY
SURFACE LOW OVER QUEBEC AND A TRIPLE POINT SURFACE LOW FORMING
NEAR THE COAST OF MAINE BY TUESDAY NIGHT. MOST OF THE GUIDANCE IS
CLOSE WITH THE EVOLUTION OF THE LONG WAVE TROUGH (ALTHOUGH THE 00Z
CMC IS SLIGHTLY MORE AMPLIFIED ALOFT), AND THE SURFACE LOW IS
DISPLACED SOUTH OF THE MODEL CONSENSUS WITH THE CMC AS WELL.
OTHERWISE, THE MODEL DIFFERENCES WITH THE SURFACE LOWS HAS
IMPROVED COMPARED TO EARLIER MODEL RUNS.
MID LEVEL TROUGH TRACKING FROM DESERT SOUTHWEST TO THE DEEP SOUTH
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL BLEND THROUGH 18Z WEDNESDAY, THEN 00Z
ECMWF/00Z EC MEAN/12Z NAM
CONFIDENCE: MODERATE
THE MODELS ARE IN GENERALLY GOOD AGREEMENT WITH THIS SOUTHERN
STREAM STORM SYSTEM THROUGH WEDNESDAY AFTERNOON, AFTER WHICH THE
GFS BECOMES MORE PROGRESSIVE COMPARED TO THE OTHER MODELS. THE
00Z UK IS STRONGER WITH THAT LOW AND THE CMC IS STRONGER WITH THE
UPSTREAM RIDGE OVER THE ROCKIES.
SURFACE LOW TRACKING FROM WESTERN CANADA TO THE NORTHERN PLAINS
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 12Z GFS/00Z ECMWF/00Z CMC
CONFIDENCE: MODERATE
A CLIPPER TYPE SURFACE LOW TRACKS SOUTHEASTWARD OUT OF ALBERTA AND
REACHES THE NORTHERN PLAINS BY WEDNESDAY MORNING IN PROGRESSIVE
NORTHWEST FLOW ALOFT. THE 00Z UKMET IS A BIT FASTER WITH THE
ARRIVAL OF THIS LOW, AND THE 12Z NAM IS A LITTLE STRONGER WITH THE
UPPER LEVEL TROUGH THAT ACCOMPANIES IT. A BLEND OF THE WELL
CLUSTERED GFS/ECMWF/CMC SHOULD WORK AS AN INITIAL BLEND FOR THIS
REGION.
MODEL TRENDS AT WWW.WPC.NCEP.NOAA.GOV/HTML/MODEL2.SHTML
500 MB FORECASTS AT WWW.WPC.NCEP.NOAA.GOV/H5PREF/H5PREF.SHTML
HAMRICK
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