011
FXUS10 KWNH 151846
PMDHMD
MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
245 PM EDT FRI MAY 15 2020
VALID MAY 15/1200 UTC THRU MAY 19/0000 UTC
...SEE NOUS42 KWNO (ADMSDM) FOR THE STATUS OF THE UPPER AIR
INGEST...
12Z MODEL EVALUATION INCLUDING FINAL PREFERENCES AND CONFIDENCE
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
19Z UPDATE: THE MODELS REMAIN IN EXCELLENT AGREEMENT AFTER THE
ARRIVAL OF THE NON-NCEP GUIDANCE FOR THE WEST COAST REGION IN
REGARDS TO THE SYNOPTIC SCALE UPPER LEVEL TROUGH BUILDING IN BY
SUNDAY AND INTO MONDAY. WITH THE DOWNSTREAM RIDGE ACROSS THE
PLAINS, THE 12Z GFS REMAINS SLIGHTLY WEAKER WITH THE RIDGE AXIS
AND THE 12Z CMC IS SLIGHTLY STRONGER ACROSS THE SOUTHERN PLAINS BY
MONDAY EVENING WITH THE RIDGE. THE 12Z UKMET TRENDED FASTER WITH
THE DISTURBANCE CROSSING THE GULF COAST REGION, HOWEVER THERE IS
STILL SOME ENSEMBLE SUPPORT FROM BOTH THE ECENS AND GEFS FOR A
SLOWER SOLUTION HERE. ACROSS THE GREAT LAKES AND OHIO VALLEY
REGION FOR DAY 3, THE 12Z NAM REMAINS THE MOST PRONOUNCED WITH THE
EVOLVING UPPER LEVEL CUT-OFF LOW, WHILST THE UKMET AND CMC ARE
MORE INDICATIVE OF AN OPEN WAVE AT 500MB AT THE END OF THE
FORECAST PERIOD. FINALLY FOR THE DISTURBANCE OFF THE SOUTHEAST
COAST, THE 12Z ECMWF IS INITIALLY DISPLACED TO THE NORTHEAST WITH
THE LOW NEAR THE NORTHERN BAHAMAS AND ANOTHER NEAR SOUTH FLORIDA
TONIGHT, AND THEN IS A BIT FARTHER OFFSHORE AS IT TRACKS NORTH AND
THEN NORTHEASTWARD. IN CONTRAST, THE GFS AND CMC ARE FARTHER WEST
AND THUS CLOSER TO THE COAST, WITH NONE OF THE GUIDANCE CURRENTLY
INDICATING A LANDFALL OVER NORTH CAROLINA AT THIS TIME. GIVEN THE
DIFFERENCES NOTED WITH THE ECMWF, A GREATER EMPHASIS WILL NOW BE
PLACED ON THE 00Z ECENS MEAN. OTHERWISE NO BIG CHANGES TO THE
EXISTING MODEL PREFERENCES.
SHORTWAVE AND SURFACE LOW TRACKING ACROSS THE NORTHEAST THROUGH
TONIGHT
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL BLEND
CONFIDENCE: HIGH
THE MODELS AND ENSEMBLE MEANS ARE IN VERY GOOD AGREEMENT WITH THIS
SYSTEM AND THUS A GENERAL DETERMINISTIC MODEL BLEND CAN BE
INCORPORATED.
SHORTWAVE AND SURFACE LOW TRACKING ACROSS THE NORTHERN TIER STATES
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL BLEND THROUGH 00Z MONDAY, THEN 12Z
ECMWF/00Z EC MEAN/12Z GFS BLEND
CONFIDENCE: MODERATE
A SHORTWAVE PERTURBATION INITIALLY OVER THE NORTHERN ROCKIES
FRIDAY WILL EVOLVE INTO A CLOSED UPPER LOW AS IT TRACKS ACROSS THE
NORTHERN PLAINS AND UPPER MIDWEST OVER THE UPCOMING WEEKEND. THIS
LOW IS EXPECTED TO BECOME CUT-OFF FROM THE NORTHERN STREAM
WESTERLIES BY EARLY IN THE WEEK ACROSS THE LOWER GREAT LAKES AND
OHIO VALLEY REGION, AND THEN SLOW DOWN IN ITS FORWARD PROGRESS.
THIS WILL SUPPORT SURFACE CYCLOGENESIS ACROSS THE MIDWEST AND
TRACK EASTWARD ACROSS THE LOWER GREAT LAKES ALONG A FRONTAL ZONE.
THERE IS DECENT OVERALL MODEL AGREEMENT THROUGH SUNDAY EVENING,
AFTER WHICH THE NAM BECOMES MORE AMPLIFIED WITH THE CLOSED LOW
DROPPING FARTHER SOUTH, CMC WEAKER, AND THE UKMET MORE
PROGRESSIVE. THE 12Z GFS IS NOTED AS BEING WEAKER WITH THE
BUILDING UPSTREAM RIDGE ACROSS THE PLAINS BY LATE IN THE FORECAST
PERIOD.
DEEP UPPER LEVEL TROUGH DEVELOPING ALONG THE WEST COAST BY MONDAY
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL BLEND
CONFIDENCE: MODERATE-HIGH
A LARGE CLOSED MID/UPPER LEVEL LOW IS FORECAST TO MOVE FROM THE
EASTERN PACIFIC TOWARD THE PACIFIC NORTHWEST COAST THROUGH THE
PERIOD. GIVEN THE HIGHLY AMPLIFIED PATTERN, THE MODEL GUIDANCE
SHOWS ABOVE AVERAGE AGREEMENT, WITH ONLY SOME MINOR DIFFERENCES AT
500 MB ON DAY 3 NOTED WITH THE SLIGHTLY STRONGER 12Z NAM SOLUTION.
AT THE SURFACE A LOW WILL APPROACH THE COAST AND THEN WASH OUT BY
DAY 3 AS THE OVERALL SYSTEM SLOWS DOWN OFF THE COAST. THIS
SYNOPTIC SCALE FEATURE AND THUS THE WESTERN THIRD OF THE U.S. HAS
THE BEST OVERALL MODEL AGREEMENT COMPARED TO THE OTHER WEATHER
SYSTEMS ACROSS THE NATION, AND THEREFORE A GENERAL MODEL BLEND CAN
BE INCORPORATED.
SOUTHERN STREAM TROUGH TRACKING FROM TEXAS AND ALONG THE GULF COAST
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 12Z GFS/12Z ECMWF
CONFIDENCE: MODERATE
A RELATIVELY WEAK SOUTHERN STREAM TROUGH WILL MOVE ACROSS THE
SOUTHERN PLAINS THROUGH EARLY SATURDAY, AND GRADUALLY THE MID
LEVEL LOW CROSSES THE GULF COAST STATES BY LATE IN THE WEEKEND.
THE 12Z NAM IS A LITTLE FARTHER NORTH WITH THE 700MB LOW ACROSS
TEXAS, AND THIS RESULTS IN LESS QPF COMPARED TO THE OTHER MODELS
THROUGH SATURDAY EVENING. THE UKMET IS NOTED AS A SLOWER SOLUTION
BY MONDAY, AND THEREFORE HEAVIER QPF ACROSS THE CENTRAL GULF COAST
REGION. A BLEND OF THE ECMWF/GFS WOULD SERVE AS A GOOD STARTING
POINT SINCE THERE IS DECENT ENSEMBLE SUPPORT FOR THIS INITIAL
BLEND.
LOW PRESSURE DEVELOPING NEAR THE BAHAMAS
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 12Z GFS/12Z GEFS/00Z ECENS BLEND
CONFIDENCE: MODERATE
THE NATIONAL HURRICANE CENTER IS CURRENTLY MONITORING AN AREA OF
DISTURBED WEATHER OVER THE WESTERN BAHAMAS IN ASSOCIATION WITH A
WEAK AREA OF LOW PRESSURE. THIS IS FORECAST TO DEVELOP FURTHER
OFF THE SOUTHERN FLORIDA COAST THROUGH FRIDAY EVENING AND
GRADUALLY MOVE TOWARD THE BAHAMAS SATURDAY MORNING BEFORE TURNING
NORTHWARD THIS WEEKEND. FORECAST GUIDANCE AGREEMENT AND
CONFIDENCE REMAINS AVERAGE AT BEST AND BEGINS TO DIVERGE BEYOND 48
HOURS. THE 00Z UKMET REMAINS SOUTHEAST OF THE MODEL CONSENSUS AS
THE LOW LIFTS NORTHWARD FROM THE BAHAMAS. BY 12Z MONDAY, THE
ECMWF AND ITS MEAN FAVOR A SLIGHTLY EASTWARD TRACK, WHEREAS THE
GFS AND THE GEFS MEAN ARE FAVORING A SLIGHTLY MORE WESTWARD TRACK,
WITH SIMILAR INTENSITY LEVELS. ALTHOUGH THE 12Z NAM IS CLOSEST TO
THE MODEL CONSENSUS, IT IS ALSO THE STRONGEST SOLUTION AT THIS
TIME. TAKING THE ABOVE FACTORS INTO ACCOUNT AND TO MAINTAIN
PREVIOUS MODEL PREFERENCE CONTINUITY, THE FAVORED BLEND
INCORPORATES THE 12Z GFS, 00Z ECMWF, 6Z GEFS, AND 00Z ECENS. FOR
MORE INFORMATION ON THIS SYSTEM AND POTENTIAL DEVELOPMENT, SEE THE
LATEST FROM THE NATIONAL HURRICANE CENTER.
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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