419
FXUS10 KWNH 161839
PMDHMD
MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
238 PM EDT THU APR 16 2020
VALID APR 16/1200 UTC THRU APR 20/0000 UTC
...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR
INGEST...
12Z MODEL EVALUATION WITH FINAL PREFERENCES AND CONFIDENCE
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
19Z UPDATE: THERE WAS A SLIGHTLY FASTER TREND WITH BOTH THE UKMET
AND THE ECMWF ON ALL THREE SYSTEMS DISCUSSED BELOW COMPARED TO
THEIR 00Z RUNS. THE GFS REMAINS THE STRONGEST SOLUTION WITH THE
SOUTHERN STREAM SYSTEM ACROSS THE CENTRAL/SOUTHERN PLAINS BY THIS
WEEKEND. THE UKMET IS A LITTLE MORE AMPLIFIED WITH THE PACIFIC
NORTHWEST SYSTEM ACROSS OREGON WITH RESPECT TO ITS 500MB HEIGHTS.
OVERALL, THE LARGE-SCALE MODEL AGREEMENT HAS IMPROVED WITH THE
MIDWEST TO NORTHEAST STORM SYSTEM TO MERIT A MULTI-DETERMINISTIC
MODEL BLEND.
WESTERN HIGH PLAINS TROUGH CROSSING THE MIDWEST AND THEN REACHING
THE EAST COAST
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: DETERMINISTIC MULTI-MODEL BLEND
CONFIDENCE: MODERATE-HIGH
A POSITIVELY TILTED TROUGH ACROSS THE ROCKIES AND NORTHERN PLAINS
IS FORECAST TO CROSS THE MIDWEST AND REACH THE EAST COAST BY
SATURDAY AFTERNOON, WHILE SUPPORTING A SURFACE LOW THAT DEVELOPS
ALONG A FRONTAL ZONE AND CROSSES THE OHIO VALLEY AND THEN EXITING
THE COAST JUST SOUTH OF NEW ENGLAND. THE 00Z ECMWF/UKMET HAVE
CONSISTENTLY BEEN SLOWER WITH THE MID LEVEL FEATURE AND THE
SURFACE WAVE, AND THE 12Z GFS HAS TRENDED A LITTLE BIT CLOSER TO
THESE MODELS, SO THIS MODEL TRIO WOULD WORK WELL AS A BLEND HERE.
THE NAM IS A LITTLE SLOWER WITH THE PROGRESSION OF THE UPPER
TROUGH ACROSS THE MIDWEST AND OHIO VALLEY, BUT SIMILAR WITH
SURFACE LOW FEATURES. IT SHOULD BE NOTED THAT AS THE SURFACE LOW
DEEPENS OFF THE NEW ENGLAND COAST SAT, THE 00Z UKMET BECOMES
FASTER THAN THE 00Z ECMWF/00Z ECMWF ENSEMBLE MEAN. BY THAT TIME,
MOST OF THE SENSIBLE WEATHER IS EXPECTED TO BE OFF THE COAST.
CLOSED LOW NEAR CALIFORNIA EVOLVING INTO OPEN WAVE OVER SOUTHERN
PLAINS
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 12Z ECMWF/UKMET/CMC BLEND
CONFIDENCE: MODERATE
AS THE CLOSED MID LEVEL LOW INITIALLY OFF THE CALIFORNIA COAST
DROPS SOUTHEASTWARD ACROSS THE DESERT SOUTHWEST, IT OPENS UP INTO
A LONG WAVE TROUGH. TRAILING SHORTWAVE ENERGY FROM NORTHERN
CALIFORNIA FOLLOWS A PATH SIMILAR TO THE FIRST MID LEVEL WAVE
LATER IN THE PERIOD. THESE TWO FEATURES EVENTUALLY CONSOLIDATE
OVER THE SOUTHERN ROCKIES AND BECOME A WELL-DEVELOPED SOUTHERN
STREAM TROUGH OVER THE CENTRAL/SOUTHERN PLAINS BY SUNDAY. THE
INTERACTION BETWEEN THE TWO SHORT WAVES IS CAUSING SOME ISSUES FOR
THE GUIDANCE, WITH THE 00Z CMC CONSOLIDATING THESE SHORTWAVES THE
QUICKEST AND THE GFS REMAINING THE MOST AMPLIFIED WITH THE SECOND
TROUGH ACROSS ARIZONA SATURDAY EVENING. THE GFS BECOMES MORE
PROGRESSIVE BY THE END OF THE FORECAST PERIOD ACROSS THE PLAINS
AND ALSO AHEAD OF ITS ENSEMBLE MEAN.
SHORT WAVE OVER THE PACIFIC NORTHWEST THIS WEEKEND
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 12Z GFS/12Z ECWMF/00Z EC MEAN BLEND
CONFIDENCE: MODERATE
SHORT WAVE ENERGY DROPPING ACROSS WESTERN CANADA AFTER FRIDAY
MORNING STARTS ERODING THE MID LEVEL RIDGING ACROSS THE PACIFIC
NORTHWEST, EVENTUALLY FORMING A CLOSED MID LEVEL LOW OVER
WASHINGTON AND OREGON BY SUNDAY MORNING. THERE IS GOOD OVERALL
MODEL AGREEMENT THROUGH SATURDAY AFTERNOON, AFTER WHICH THE 12Z
NAM BECOMES STRONGER WITH THE UPPER LOW ACROSS OREGON AND A BIT
MORE PROGRESSIVE. THE UKMET IS SLIGHTLY WEAKER AND THE ECMWF IS A
LITTLE SLOWER. GIVEN THAT THERE IS STILL A FAIR AMOUNT OF SPREAD
WITH THE SPEED AND MAGNITUDE OF THE MID LEVEL SYSTEM, FORECAST
CONFIDENCE IS ONLY MODERATE AT THIS TIME.
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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