894
FXUS10 KWNH 160443
PMDHMD
MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1242 AM EDT MON SEP 16 2019
VALID SEP 16/0000 UTC THRU SEP 19/1200 UTC
...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR
INGEST...
00Z MODEL EVALUATION WITH PREFERENCES AND FORECAST CONFIDENCE
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
...DEEP LATITUDE WESTERN TROF ENTERING THE WEST; REINFORCED BY
CLOSED LOW LATE TUES...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL BLEND FIRST SHORTWAVE; NON-CMC SECOND
SHORTWAVE
CONFIDENCE: SLIGHTLY ABOVE AVERAGE
FAIRLY GOOD AGREEMENT IN THE LATEST MODEL GUIDANCE THAT A PAIR OF
SHORTWAVES WILL WORK THROUGH THE PACIFIC NORTHWEST AND INTO THE
NORTHERN ROCKIES AND NORTHERN PLAINS DURING THE FORECAST PERIOD.
FIRST SHORTWAVE THAT IS CURRENTLY MOVING ONSHORE THE WEST COAST
WILL ROTATE QUICKLY INTO MONTANA AND NORTH DAKOTA BY DAY 2. HERE,
EARLIER DISCREPANCIES BETWEEN THE UKMET AND THE REST OF THE
GUIDANCE WITH RESPECT TO THE SPEED HAVE MOSTLY BEEN RESOLVED. THE
UKMET MIGHT REMAIN A BIT FASTER THAN THE OTHERS, BUT A GENERAL
MODEL BLEND SHOULD PROVIDE A REASONABLE SOLUTION. THE SECONDARY
SHORTWAVE THAT THEN DROPS INTO THE PACIFIC NORTHWEST BY DAY 2/3 IS
FAIRLY AGREED ON. THE ONE EXCEPTION WOULD BE THE 12Z CMC, WHICH IS
TOO FAR SOUTH AND AMPLIFIED WITH THE CLOSED LOW, AS IT TAKES IT
INTO NORTHERN CALIFORNIA. MEANWHILE, THE REST OF THE GUIDANCE IS
NORTH ACROSS OREGON AND MORE POSITIVELY TITLED.
...SOUTHWEST SHORTWAVE, MOVING THROUGH CENTRAL HIGH PLAINS INTO
NORTHERN PLAINS/MN BY TUESDAY...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL BLEND
CONFIDENCE: SLIGHTLY ABOVE AVERAGE
WEAK SHORTWAVE OVER THE FOUR CORNERS REGION CURRENTLY SEEN IN
WATER VAPOR IMAGERY WILL CONTINUE TO DRIFT NORTH/NORTHEAST OVER
THE FORECAST PERIOD AND GRADUALLY BECOME ABSORBED INTO THE LARGE
SCALE TROUGHING OVER THE WESTERN US. THE SHORTWAVE IS EXPECTED TO
REACH THE CENTRAL PLAINS LATE MONDAY AND THEN INTO THE NORTHERN
PLAINS AND UPPER MIDWEST BY TUESDAY. THE VARIOUS DETERMINISTIC
MODELS OFFER FAIRLY SIMILAR SOLUTIONS WITH JUST SLIGHTLY VARYING
DEGREES OF STRENGTH AND TIMING (CMC A BIT FAST; ECMWF
SLOWER/WEST). OVERALL, A GENERAL MODEL BLEND IS PREFERRED.
..GULF OF MEXICO TROPICAL WAVE
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 2/3RD UKMET, 1/3RD GFS BLEND
CONFIDENCE: AVERAGE TO SLIGHTLY BELOW AVERAGE
GUIDANCE HAS COME INTO BETTER AGREEMENT THAT A WEAK SURFACE WAVE
MOVING WESTWARD OVER THE CENTRAL/WESTERN GULF OF MEXICO WILL
GRADUALLY TAKE ON BETTER ORGANIZATION IN THE NEXT FEW DAYS AS IT
APPROACHES THE TEXAS GULF COAST. THE SYSTEM IS EXPECTED TO PRODUCE
LOCALLY HEAVY RAINFALL SOMEWHERE ALONG THE COAST BY DAY 3.
GUIDANCE HAS SOME LATITUDINAL DIFFERENCES BUT FOR NOW, A CONSENSUS
OF THE GFS AND UKMET (WITH MORE INCLUSION OF THE UKMET BY DAY 3)
IS PREFERRED. FORECAST CONFIDENCE IS AVERAGE AT FIRST, THEN DROPS
TO SLIGHTLY BELOW AVERAGE BY DAY 3.
..HURRICANE HUMBERTO
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: OFFICIAL NHC FORECAST
BEST PROXY: 18Z GFS
CONFIDENCE: BELOW AVERAGE
HURRICANE HUMBERTO CONTINUES TO STRENGTHEN GIVEN WARM WATERS AND
FAVORABLE ENVIRONMENTAL CONDITIONS. ITS SLOW MOTION HAS TAKEN A
GRADUAL NORTH/NORTHEAST DIRECTION AND THIS IS EXPECTED OVER THE
NEXT SEVERAL DAYS. THE LATEST GUIDANCE IS IN REASONABLE AGREEMENT
WITH THE OFFICIAL NHC ADVISORY TRACK THROUGH ABOUT 24-36 HOURS,
BUT BEYOND THAT, THERE IS SIZABLE SPREAD IN THE LATEST MODEL
GUIDANCE. THE NAM AND UKMET ARE THE FASTER SOLUTIONS, AS HUMBERTO
GETS PICKED UP IN THE APPROACHING MID-LATITUDE TROUGH EARLIER.
MEANWHILE, THE CMC/ECMWF STALL THE SYSTEM MUCH LONGER AND
THEREFORE ARE THE SLOWEST AND FURTHER SOUTH SOLUTIONS BY DAY 3.
FOR THIS CYCLE, THE GFS IS THE BEST PROXY FOR THE TRACK THROUGH
THE ENTIRE FORECAST PERIOD, ALTHOUGH THERE REMAINS SOME DEVIATIONS
FROM THE LATEST OFFICIAL NHC TRACK. IN GENERAL, FORECAST
CONFIDENCE DROPS OFF CONSIDERABLY BEYOND 36-48 HOURS.
MODEL TRENDS AT WWW.WPC.NOAA.GOV/HTML/MODEL2.HTML
500 MB FORECASTS AT WWW.WPC.NOAA.GOV/H5PREF/H5PREF.SHTML
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