640
FXUS10 KWNH 240621
PMDHMD
MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
221 AM EDT SAT AUG 24 2019
VALID AUG 24/0000 UTC THRU AUG 27/1200 UTC
...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR
INGEST...
00Z MODEL EVALUATION INCLUDING PREFERENCES AND FORECAST CONFIDENCE
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
..OVERALL PATTERN ACROSS THE CONUS
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL BLEND
EXCEPTION(S): 12Z UKMET/ECMWF FL AND OFF CAROLINAS DAYS 2/3.
NON-UKMET ACROSS NORTHERN TIER DAY 2/3.
CONFIDENCE: SLIGHTLY ABOVE AVERAGE
AVERAGE FOR SURFACE LOW OFF CAROLINAS.
07Z UPDATE: THE 00Z ECMWF AND UKMET BOTH TRENDED A BIT WEAKER FOR
THE FL/CAROLINA NEAR WATERS CYCLONE, MORE IN LINE WITH INITIAL
THINKING THAT THE 12Z RUNS WERE A BIT TOO STRONG, BUT THE
PLACEMENT/TIMING REMAINS SOLID FOR CONTINUED PREFERENCE. THE 00Z
CMC REMAINS WEAK.
THE UKMET CONTINUES TO BE STRONGER/FURTHER SOUTH WITH THE CLOSED
LOW/SURFACE WAVE ACROSS THE NORTHERN TIER AND WITH THE 00Z
ECMWF/CMC KEEPING WITH CONTINUITY, WILL SUGGEST CONTINUING A
NON-UKMET BLEND FOR THIS SYSTEM.
---PRIOR DISCUSSION---
STRONG MODEL AGREEMENT CONTINUES THROUGH THIS FORECAST PERIOD
AGAIN PROVIDING SOLID CONFIDENCE ACROSS MUCH OF THE CONUS. THERE
ARE SMALL DETAIL DIFFERENCES ACROSS THE NORTHERN TIER ON DAY 3,
WITH THE 12Z UKMET A DEVELOPING/DEEPENING A BIT FURTHER SOUTH,
ENOUGH TO DISPLACE IT WITHIN THE LARGER GUIDANCE SUITE. THE 00Z
NAM AND GFS TRENDED A BIT MORE AMPLIFIED WITH THE SECONDARY
SHORTWAVE CROSSING SW CANADA LATE MONDAY TO REINFORCE THE
BROADENING CLOSED LOW INTO THE RED RIVER VALLEY AND SOUTH CENTRAL
CANADA BY 12Z TUESDAY, BUT TO LIMITED NEGATIVE EFFECTS.
AS THE NORTHERN STREAM TROF AMPLIFIES AND DIGS INTO THE LOWER
MISSISSIPPI RIVER VALLEY AND INTERACTS WITH THE NORTHEASTWARD
SHIFTING TROPICAL WAVE, THE NAM IS A BIT MORE SEPARATED AND
STRONGER WITH EACH FEATURE (TYPICAL OF BIAS). THIS DELAYS ITS
EASTWARD PROGRESSION ACROSS THE GULF COAST STATES, RELATIVE TO THE
GFS/ECMWF/CMC, THOUGHT THE UKMET IS SLOWER WITH THE MOISTURE
STREAM ALLOWING FOR SOME AGREEMENT IN THE QPF PLACEMENT, THIS IS
LESS PREFERRED OVERALL.
THE 00Z GFS CONTINUES THE SHORT-TERM TREND TOWARD AT LEAST
PLACEMENT OF THE SURFACE WAVE MOVING OUT OF FL INTO THE GULF
STREAM OFF THE CAROLINA COAST SUN INTO MONDAY. LIKE THE 12Z CMC,
THE GFS IS QUITE WEAK BUT SHOWS AT LEAST SOME CONFIDENCE IN THE
TRACKING/TIMING. THE ECMWF/UKMET BOTH CONTINUE TO BE VERY STRONG
WITH THE WAVE AND SLIGHTLY FASTER. THINKING BOTH MAY BE A BIT TOO
STRONG/DEEP BUT STILL FAVOR A BLEND OF THE UKMET/ECMWF OVER OTHER
GUIDANCE BLENDS. THE 00Z NAM IS NOW THE SLOWEST, BUT IS MIDDLE
GROUND IN STRENGTH/DEPTH. CONFIDENCE REMAINS AVERAGE FOR THIS
SYSTEM GIVEN THE MODEST REMAINING SPREAD, ESPECIALLY IN STRENGTH.
OVERALL SPREAD CONTINUES TO REDUCE WITH RESPECT TO TS IVO, UNTIL
LATE DAY 2 INTO DAY 3. THIS IS WHEN THE SURFACE CYCLONE WILL BE
WEAKENING/BECOMING SHALLOW, SO STEERING FLOW WILL BE HIGHLY
DETERMINED BY REMAINING CONVECTION/DEPTH, SO THE 00Z GFS CONTINUES
TO BE QUICKEST TO REMOVE CONVECTION AND SO THE SURFACE WAVE STALLS
RELATIVE TO THE REMAINING FASTER ECMWF/UKMET. NHC FORECAST SEEMS
TO JIVE BEST WITH THE GFS/NAM AND ECMWF. THE GFS CONTINUES TO BE
THE MOST EASTWARD WITH THE MOISTURE FEED INTO THE DESERT SOUTHWEST
AND GIVEN ITS TRACK RECORD OVER THE LAST DAY OR SO, IT SEEMS MORE
LIKELY TO WEIGHT THE GFS HIGHEST IN BLENDS FOR THIS AREA.
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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