514
FXUS10 KWNH 180435
PMDHMD
MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1235 AM EDT FRI OCT 18 2019
VALID OCT 18/0000 UTC THRU OCT 21/1200 UTC
...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR
INGEST...
00Z MODEL EVALUATION WITH PREFERENCES AND CONFIDENCE
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
WESTERN TROUGH AND SECONDARY SHORTWAVE ENERGY EJECTING INTO
CENTRAL PLAINS...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL BLEND THROUGH 48 HOURS; ECMWF/GFS BLEND
(WEIGHTED TOWARD ECMWF) AFTER
CONFIDENCE: AVERAGE
LONGWAVE TROUGHING CURRENTLY OVER THE WESTERN U.S. IS EXPECTED TO
MOVE INTO THE CENTRAL PLAINS FRIDAY INTO FRIDAY NIGHT, SPAWNING A
COMPACT SURFACE LOW IN THE LEE OF THE ROCKIES THAT DROPS INTO
TEXAS BY SATURDAY. HERE, THE LATEST MODEL GUIDANCE IS IN
REASONABLE AGREEMENT WITH SYNOPTIC FEATURES, WITH PERHAPS THE GFS
BEING A TOUCH FASTER COMPARED TO THE REST OF THE GUIDANCE. A
GENERAL MODEL BLEND IS SUFFICIENT.
A SECONDARY, STRONGER SHORTWAVE TROUGH WILL THEN PUSH INTO THE
PACIFIC NORTHWEST SATURDAY AND EVENTUALLY TAKE ON A NEGATIVE TILT
AND CLOSE OFF OVER THE CENTRAL PLAINS. THE GFS IS THE MOST
AGGRESSIVE WITH THIS IDEA, CLOSING OFF 6-12 HOURS EARLIER THAN THE
REST OF THE GUIDANCE. THE MOST SIGNIFICANT DIFFERENCES IN THE
GUIDANCE SHOW UP BY 72 HOURS (21.00Z), PARTICULARLY AT THE SURFACE
WHERE A DEEP LOW IS EXPECTED TO FORM IN THE HIGHLY DIFFLUENT FLOW
ALOFT. THE NAM IS THE MOST WRAPPED UP (FURTHER NORTH) WHILE THE
UKMET IS FURTHEST SOUTH, MORE SO OVER NEBRASKA. THE GFS/ECMWF
OFFER A GOOD COMPROMISE SOLUTION AT FIRST, BUT THEN DIVERGE WITH
RESPECT TO HOW FAST THE LOW LIFTS NORTHEAST INTO THE UPPER MIDWEST
(GFS FAST, EC SLOWER). TAKING ALL OF THIS INTO CONSIDERATION, A
GENERAL MODEL BLEND CAN BE APPLIED FOR THE FIRST 48 HOURS, THEN A
SOLUTION CONSISTING MAINLY THE ECMWF/GFS IS PREFERRED, WITH HIGHER
WEIGHT TOWARD THE ECMWF.
POTENTIAL TROPICAL CYCLONE SIXTEEN
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: SEE LATEST NHC ADVISORY
BEST PROXY: 00Z GFS
IN THE LAST 24 HOURS, THE MODEL GUIDANCE HAS COME INTO BETTER
AGREEMENT WITH THE EVOLUTION OF PTC 16 AS IT BEGINS TO TURN
NORTH/NORTHEAST TOWARD THE FL PANHANDLE IN THE NEXT 24-36 HOURS.
THE 00Z GFS AND 12Z UKMET REMAIN A BIT FASTER AND FURTHER TO THE
EAST COMPARED TO THE ECMWF/CMC SOLUTIONS BUT THE OVERALL SPREAD
HAS COME DOWN SIGNIFICANTLY SINCE 24 HOURS AGO. THE 00Z NAM IS A
TOUCH SLOW, BY ABOUT 6 HOURS, BUT IS WITHIN THE MODEL SPREAD FOR
POSITION AS IT MOVES INLAND EARLY TO MID-DAY SATURDAY. LOOKING AT
THE LATEST ENSEMBLE MEMBERS, THERE IS OVERALL VERY GOOD CLUSTERING
WITH THE TRACK GUIDANCE, WHICH BUMPS UP THE FORECAST CONFIDENCE. A
BLEND OF THE AVAILABLE GUIDANCE WOULD YIELD A FAIRLY CLOSE PROXY
TO THE OFFICIAL NHC TRACK, WITH PERHAPS THE GFS BEING THE BEST
PROXY AT THIS POINT.
AS THE SYSTEM MOVES BACK INTO THE OPEN WATERS OFF THE NORTH
CAROLINA COAST ON SUNDAY, THERE REMAINS SOME QUESTIONS ON WHETHER
THE SYSTEM TAKES A NORTHWARD JOG OR HEADS MORE EASTERLY. SOME
MODELS DISSIPATE/ABSORB THE SYSTEM JUST BEYOND 84 HOURS. FOR NOW,
THE 00Z GFS STILL OFFERS THE BEST PROXY TO THE OFFICIAL FORECAST,
THOUGH THE FORECAST SPREAD (AND FORECAST CONFIDENCE) BECOMES
LARGER AFTER 72 HOURS.
MODEL TRENDS AT WWW.WPC.NOAA.GOV/HTML/MODEL2.HTML
500 MB FORECASTS AT WWW.WPC.NOAA.GOV/H5PREF/H5PREF.SHTML
TAYLOR
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