864
FXUS10 KWNH 131829
PMDHMD
MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
129 PM EST THU FEB 13 2020
VALID FEB 13/1200 UTC THRU FEB 17/0000 UTC
...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR
INGEST...
12Z MODEL EVALUATION WITH PREFERENCES & CONFIDENCE
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
OVERALL PATTERN ACROSS THE CONUS
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL BLEND
EXCEPTION: 12Z GFS/NAM/UKMET BLEND FOR LATE SAT/SUNDAY IN PACIFIC
NW
CONFIDENCE: ABOVE AVERAGE BUT SLIGHTLY BELOW AVERAGE FOR EXCEPTION
19Z UPDATE FOR THE PACIFIC NORTHWEST DAY 3: THE 12Z NON-NCEP SUITE
TRENDED TOWARD THE GFS/NAM, THOUGH THE ECMWF/CMC SLOWED, THEY ARE
BOTH MUCH WEAKER AND STILL APPEARS TO BE OUT OF TOLERANCE RELATIVE
TO THE INITIAL PREFERENCE TO HAVE INCLUDED BUT HAVE SOME INCREASE
IN OVERALL CONFIDENCE. THE UKMET SLOWED AS WELL BUT ALSO SHOWED
GREATER AMPLIFICATION, AND WHILE A TAD SLOWER THAN THE INITIAL
PREFERENCE, THERE BETTER CONGRUENCE FOR INCLUSION IN THE BLEND.
SO A GFS/NAM/UKMET BLEND IS PREFERRED BUT STILL AT SLIGHTLY BELOW
AVERAGE CONFIDENCE.
---PRIOR DISCUSSION---
A VERY QUIET LARGE SCALE PATTERN ACROSS THE CONUS IS INITIALLY
DOMINATED BY A LARGE ARCTIC HIGH PRESSURE AREA ACROSS THE PLAINS
TODAY THAT IS PRESSING A LINGERING WARM CONVEYOR/FRONTAL ZONE
ACROSS THE EAST COAST TODAY INTO EARLY TOMORROW (FRI). GUIDANCE
AS BEEN QUITE AGREEABLE WITH BOTH THE EXITING SYSTEM AND THE HIGH
AS IT DOMINATES THE EASTERN HALF OF THE CONUS THROUGH SUNDAY.
THE ACTIVE AREA WILL BE THE PACIFIC NORTHWEST, WHERE A FEW
SHORTWAVES WILL CROSS THE AREA THROUGH THE SHORT-TERM FORECAST
PERIOD. THE FIRST, CURRENTLY IMPACTING VANCOUVER ISLAND WILL
PRESS THROUGH WASHINGTON INTO THE NORTHERN ROCKIES THROUGH TODAY
AND TOMORROW. AS IT SLIDES EASTWARD, THE MAIN ENERGY AND QPF WILL
REMAIN ALONG/JUST NORTH OF THE US/CANADIAN BOARDER WITH SOME
INCREASE OF GREAT LAKES QPF BY SUNDAY. WHILE THERE IS SOME
SPREAD, A GENERAL MODEL BLEND WILL SUFFICE GIVEN THE TIMING/SHAPE
IS GOOD ACROSS THE CONUS. A WEAK SHORTWAVE WILL PROGRESS THROUGH
BC INTO SATURDAY, CONTINUING TO DIRECT MOISTURE/ONSHORE JET ACROSS
THE PACIFIC NW, AFFECTING MAINLY OROGRAPHIC QPF, BUT GENERAL
DISTURBED WEATHER, WITH VERY LITTLE LARGE SCALE MODEL SPREAD TO
GET TOO PICKY ABOUT.
~~~ PACIFIC NORTHWEST DAY 3 ~~~
HOWEVER, BY LATE SATURDAY, THE NEXT MORE AMPLIFIED SHORTWAVE WILL
CROSS THROUGH THE SOUTHEAST GULF OF AK, DIRECTING TOWARD SOUTHERN
BC/WA, WITH SIZABLE TIMING DIFFERENCES. UNCHARACTERISTICALLY, THE
ECMWF, CMC ARE SLIGHTLY GREATER AMPLIFIED WITH THE LEADING EDGE OF
HEIGHT-FALLS. THE 12Z NAM/GFS CONTINUE TO FAVOR SLIGHTLY STRONGER
(INCREASING DIFFLUENCE) JET ENERGY APPROACHING THE WAVE AND
AMPLIFYING IT LATER ON SUNDAY AND CLOSER TO THE COAST COMPARED TO
THE ECMWF, WHICH IS ALREADY ASHORE. THE UKMET TYPICALLY A
BELL-WEATHER ON WHICH DIRECTION TO FAVOR, IS IN BETWEEN BUT HAS A
VERY STRONG UPPER LEVEL/FLAT JET TO NOT REALLY SIDE WITH EITHER
CAMP. THE DIFFERENCE IN THE EVOLUTION/TIMING DOES NOT AFFORD A
GENERAL MODEL BLEND/COMPROMISE IN THIS SCENARIO; AND TRADITIONAL
KNOWN NEGATIVE BIASES ARE ALSO OPPOSITE (EXAMPLE: THE NAM IS TOO
AMPLIFIED ON DAY 3, AND IT IS GENERALLY WEAKER OVERALL WITH THIS
RUN). SO THERE IS VERY LOW CONFIDENCE IN THIS SYSTEM'S TIMING,
BUT OVERALL EVOLUTION, UL JET ENHANCEMENT EVOLUTION AND LONGER
TERM TRENDS SUGGEST THE GFS/NAM MAY HAVE A SLIGHTLY BETTER HANDLE
ON THE SITUATION, WITH THE UKMET TIPPING SLIGHTLY TOWARD THIS CAMP
OVER THE FASTER ECMWF/CMC PAIR.
MODEL TRENDS AT WWW.WPC.NCEP.NOAA.GOV/HTML/MODEL2.HTML
500 MB FORECASTS AT WWW.WPC.NCEP.NOAA.GOV/H5PREF/H5PREF.SHTML
GALLINA
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