427
FXUS10 KWNH 151630
PMDHMD
MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1229 PM EDT TUE OCT 15 2019
VALID OCT 15/1200 UTC THRU OCT 19/0000 UTC
...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR
INGEST...
12Z MODEL EVALUATION WITH LATEST PREFERENCES AND CONFIDENCE
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
GREAT LAKES CLOSED LOW AND DEVELOPING NORTHEAST COASTAL SURFACE LOW
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL BLEND THRU 17.12Z
NON-NAM AND LOWER 12Z GFS WEIGHTING THEREAFTER
CONFIDENCE: SLIGHTLY ABOVE AVERAGE THRU 17.12Z...AVERAGE AFTER
CURRENTLY AN AMPLIFYING CLOSED LOW IS TRACKING INTO THE GREAT
LAKES WITH A NORTHERLY JET STREAK DESCENDING THE WESTERN SIDE
ALONG WITH STRONG BUT RELATIVELY FLAT SUBTROPICAL JET CROSSING THE
TN VALLEY. AS THE NORTHERN STREAM JET ROUNDS THE BASE, THE
SUBTROPICAL JET STREAM SUPPORTS AN INCREASING DIFFLUENT PATTERN
OVER THE MID-ATLANTIC TO SUPPORT RAPID SURFACE CYCLOGENESIS LATE
WED INTO THURSDAY MORNING. STRONG WARM CONVEYOR BELT ENHANCED BY
THE GULF STREAM AND CONVECTION WILL ACCELERATE AND FURTHER DEEPEN
THE LOW ACROSS LONG ISLAND INTO NEW ENGLAND, POTENTIALLY REACHING
RECORD LOW PRESSURE VALUES FOR OCTOBER PARTICULARLY ACROSS SE NEW
ENGLAND. GUIDANCE IS IN FAIRLY SOLID AGREEMENT THROUGH THIS TIME
PERIOD (17.12Z) TO SUPPORT A GENERAL MODEL BLEND AT SLIGHTLY ABOVE
AVERAGE CONFIDENCE.
AFTER 17.12Z, THE LATENT HEAT RELEASE, RAPID DEEPENING IS HANDLED
DIFFERENTLY IN THE TRANSFER OF THE CLOSED LOW ENERGY OUT OF THE
GREAT LAKES INTO THE COASTAL SYSTEM. THE 12Z NAM CONTINUES TO
SHOW THE MOST VERTICALLY STACKED AND DEEPEST SOLUTION, WHICH MAY
BE RELATED TO BETTER HIGHER RESOLUTION OF WARM GULF STREAM AIR,
BUT THIS VERY STRONG SIGNAL DEPARTS RAPIDLY FROM THE OTHER
GUIDANCE MEMBERS AND ENSEMBLE SUITE/TREND, LEAVING IT OUT OF THE
PREFERENCE QUICKLY (YET MAY NOT BE FULLY UNREALISTIC). THE GFS
WHICH HAS BEEN TYPICALLY WEAK, HAS TRENDED A BIT DEEPER AND SHOWS
A STALLING OVER SE NEW ENGLAND LIKE THE ECMWF/UKMET/CMC SOLUTIONS,
BUT WHILE THE MASS FIELDS ALOFT TRANSLATE NORTHEAST INTO SE CANADA
IN LINE WITH OTHER GUIDANCE, THE GFS CONTINUES TO SUPPORT A
SURFACE WAVE THROUGH THE GULF OF MAINE AND NOVA SCOTIA WELL ON THE
EASTERN SIDE OF THE ENSEMBLE SUITE. THE GEFS MEAN, HELPS TO
ADJUST FOR THE OPERATIONAL RUN, BUT THE MODERATE SPREAD IN THE
SUITE DENOTES THE GFS OVERALL UNCERTAINTY AFTER THIS POINT. THE
ECMWF/ECENS SHOW MODERATE SPREAD OF SOLUTIONS A BIT LATER IN THE
FORECAST PERIOD FURTHER INTO CANADA AND HAVE SUPPORT OF THE
CMC/CMCE AND UKMET. AS SUCH A NON-NAM BLEND IS SUPPORTED AFTER
17.12Z, WITH MORE GEFS THAN GFS IN THE WEIGHTING. CONFIDENCE IS
AVERAGE AFTER 17.12Z.
SHORT WAVE ENERGY AFFECTING TEXAS THROUGH MIDWEEK SHEARING THRU
EASTERN GULF STATES BY FRI
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 12Z NAM AND 00Z CMC/UKMET BLEND
CONFIDENCE: AVERAGE
GOES-WV SUITE DENOTES A POSITIVE-TILT TROF ACROSS THE DESERT
SOUTHWEST OF E AZ, W NM, WITH A WEAK CONNECTION TO THE NORTHERN
STREAM ACROSS THE TX PANHANDLE, THAT CONTINUES TO SEVER WITH TIME.
EVENTUALLY (EARLY WED), THE REMAINING SHORTWAVE ENERGY STALLS IN
IN WESTERN TX/BIG BEND REGION, WITH THE GFS SHOWING TYPICAL
FAST(EASTWARD) BIAS WITHIN THE OVERALL SUITE. BY LATE THURSDAY,
THE COMPACT WAVE WILL LIFT SHORTWAVE ENERGY OUT OF THE TROPICS
ALONG THE WESTERN PERIPHERY OF THE SUBTROPICAL RIDGE ACROSS THE SE
GULF/CUBA. THIS WILL SUPPORT INCREASED CONVECTION AND WEAK LOWER
LEVEL WAVE DEVELOPMENT WITH WEAK SURFACE WAVE IN THE CENTRAL GULF
BY 84HRS. THE GFS BEING EAST, LIFTS THE TROPICAL SHORTWAVE
ENERGY NORTH AND INTO THE COASTAL LOUISIANA, WHILE THE
NAM/CMC/UKMET ARE MORE FLAT/SHEARED INTO THE MORE CONFLUENT FLOW
IN THE EASTERN GULF. THE ECMWF SHOWS TYPICAL SLOW PROGRESSION
WITH EVENTUALLY WEAKENING THE SHORTWAVE TOO MUCH ALLOWING FOR THE
SURFACE WAVE/CONVECTION TOO FAR WEST IN THE SUITE BY THE END OF
THE FORECAST PERIOD. AS SUCH WILL FAVOR A 12Z NAM AND 00Z
UKMET/CMC BLEND AT AVERAGE CONFIDENCE.
WESTERN U.S. LONGWAVE TROUGH (WED-THURS) SHIFTS INTO ROCKIES WITH
NORTHERN PLAINS CYCLOGENESIS THURS INTO FRI
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL BLEND
CONFIDENCE: SLIGHTLY ABOVE AVERAGE
GULF OF ALASKA WAVE WILL PROGRESS TO THE PERSISTENT RIDGE ACROSS
THE WEST, SLOWLY BREAKING IT DOWN. WHILE THE MAIN INNER CORE OF
THE SHORTWAVE BREAKS DOWN AND LIFTS NORTH INTO THE PANHANDLE OF
AK, THE REMAINING LONG-WAVE TROF CONTINUES TO PRESS EASTWARD UNDER
THE INFLUENCE OF STRENGTHENING BROAD BUT FLAT PACIFIC FLOW
UPSTREAM. THIS ALLOWS FOR A CONSTANT EASTWARD PROGRESSION THROUGH
THE ROCKIES BY LATE THURSDAY INTO FRIDAY; SUPPORTING NORTHERN
PLAINS CYCLOGENESIS. THE GUIDANCE HAS BEEN VERY PERSISTENT AND
MILDLY AGREED UPON, WITH ONLY TYPICAL TIMING BIAS NOTED...IE
GFS/NAM AND UKMET A BIT FAST THE CMC/ECMWF SLOW. THIS TIMING ALSO
SUPPORTS A BIT MORE CURVATURE TO THE BASE OF THE TROF ACROSS THE
FOUR CORNERS INTO THE CENTRAL ROCKIES BY 84HRS, COMPARED TO THE
ECMWF/CMC BEING A BIT MORE SHARP AND SOUTH. OVERALL, THIS IS A
FAVORABLE SETUP/EVOLUTION FOR A GENERAL MODEL BLEND, MAINLY TO
SLOW THE FAST GUIDANCE, AND SPEED UP THE SLOW ONES. CONFIDENCE
IS SLIGHTLY ABOVE AVERAGE IN THIS BLEND.
PACIFIC NORTHWEST REINFORCING SHORTWAVE LATE THURS INTO FRI WITH
BROAD/STRONG WESTERLY PACIFIC JET THEREAFTER
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: NON-UKMET BLEND
CONFIDENCE: SLIGHTLY ABOVE AVERAGE
IN THE WAKE OF THE INITIAL LONGWAVE HEIGHT-FALLS, A FAST/ZONAL AND
STORMY FLOW WILL SETUP WITH NEARLY ALL GUIDANCE DEVELOPING A
BROAD, FLAT 140-150 25H JET ACROSS THE NORTHERN PACIFIC BY THE END
OF THE FORECAST PERIOD. AT THE NOSE OF THE JET, A WAVE WILL TRACK
INTO THE PACIFIC NORTHWEST LATE THURSDAY INTO FRIDAY, THE ECMWF,
BEING SLOW WITH THE INITIAL HEIGHT-FALLS SEES A SLIGHTLY FASTER
SOLUTION THAN THE GFS/NAM WITH A GREATER NEGATIVE TILT. THIS IS
NOT TOO OUT OF PHASE/AMPLIFICATION WITH THE GFS/NAM/CMC TO SUGGEST
KEEPING IT IN THE PREFERENCE. HOWEVER, THE 00Z UKMET IS EXTREMELY
OVER-AMPLIFIED, THOUGH IT THE CORRECT POSITION, THIS LOOKS LIKE A
TYPICAL NEGATIVE OVER-AMPLIFICATION BIAS NOTED WITH THE UKMET AND
SHOULD BE REMOVED FROM THE PREFERENCE AT THIS TIME.
MODEL TRENDS AT WWW.WPC.NOAA.GOV/HTML/MODEL2.HTML
500 MB FORECASTS AT WWW.WPC.NOAA.GOV/H5PREF/H5PREF.SHTML
GALLINA
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