384
FXUS10 KWNH 221639
PMDHMD
MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1138 AM EST WED JAN 22 2020
VALID JAN 22/1200 UTC THRU JAN 26/0000 UTC
...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR
INGEST...
12Z MODEL EVALUATION WITH PREFERENCES AND FORECAST CONFIDENCE
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~~
..CLOSED LOW OFF THE SOUTHEAST COAST
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~~
PREFERENCE: GENERAL MODEL BLEND
CONFIDENCE: ABOVE AVERAGE
CLOSED VERTICALLY STACKED LOW EAST OF FLORIDA WILL MOVE EASTWARD
AWAY FROM THE COAST THROUGH TONIGHT. SUBTLE VORTICITY LOBES
ROTATING AROUND THE MAIN CLOSED FEATURE WILL ALLOW SURFACE
TROUGHINESS TO PERSIST TOWARDS THE FL COAST MUCH OF TODAY, BUT ANY
SIGNIFICANT SENSIBLE WEATHER IMPACTS WILL REMAIN OFFSHORE. WHILE
THE NAM WAS MOST AGGRESSIVE WITH LAGGING MID-LEVEL ENERGY, IT
APPEARS THE LATEST 12Z NAM MASS FIELD IS BETTER CLUSTERED WITH THE
REST OF THE GUIDANCE RESULTING IN SIMILAR SURFACE TROUGH AXIS
PLACEMENT. THEREFORE, OPTED FOR A GENERAL MODEL BLEND FOR THIS
SYSTEM.
...SHORTWAVE MOVING FROM NEW MEXICO TOWARDS THE GULF COAST
TONIGHT...
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~~~
PREFERENCE: GEMERAL MODEL BLEND
CONFIDENCE: AVERAGE
SHORTWAVE AND ACCOMPANYING WEAK SURFACE LOW WILL DIVE SOUTHEAST
FROM NEW MEXICO THIS MORNING TO THE LOUISIANA GULF COAST TONIGHT,
BEFORE BECOMING ABSORBED IN THE LARGE MID-LEVEL VORTEX DEVELOPING
ON THURSDAY. THE OVERALL AMPLITUDE OF BOTH THE MID-LEVEL FEATURES
AND AT THE SURFACE IS WEAK, AND THERE IS GOOD AGREEMENT IN THE
EVOLUTION AMONG THE VARIOUS GLOBAL MODELS. THE NAM HAS SLOWED ITS
OVERALL PROGRESSION OF THIS SHORTWAVE AS COMPARED TO PREVIOUS
MODEL RUNS. THE ECMWF HAS GOOD SUPPORT FROM ITS ENSEMBLES, AND THE
GFS HAS ITS OWN ENSEMBLE SUPPORT, WITH SOME MINOR LATITUDINAL
DIFFERENCES SEPARATING THE TWO CAMPS. THE CMC AND UKMET IS ALSO IN
THE MIDDLE OF THE EC/GFS/NAM CLUSTERING RESULTING IN A GENERAL
MODEL BLEND.
..TROUGH MOVING ONSHORE THE PACIFIC NORTHWEST FRIDAY
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~~~
PREFERENCE: NON-12Z NAM/UKMET
CONFIDENCE: AVERAGE
A PIECE OF ENERGY SHEDDING FROM A CLOSED LOW NEAR THE GULF OF
ALASKA WILL EJECT EASTWARD INTO THE PACIFIC NORTHWEST ON FRIDAY,
ACCOMPANIED BY AN INTENSIFYING, ALTHOUGH STILL MODEST, PACIFIC JET
STREAK BRINGING HEAVY RAINFALL TO THE NORTHWEST. THE NAM CONTINUES
TO BE EXCEPTIONALLY FLAT WITH ITS AMPLITUDE OF THIS FEATURE
COMPARED TO THE GLOBAL CONSENSUS, LIKELY DUE TO A WEAKER
ANTICYCLONIC JET STREAK AND LAGGING MORE RESIDUAL ENERGY BACK INTO
THE MAIN TROUGH. THE UKMET SEEMS A BIT TOO AGRESSIVE WITH THE
MAGNITUDE OF THE SHORTWAVE, EVEN AFTER MOVING ONSHORE. SO WHILE
THE TIMING LOOKS REASONABLE COMPARED TO THE CLUSTERING, THE
AMPLITUDE AND STRENGTH OF THE SHORTWAVE WILL RESULT IN TOO HIGH OF
QPF ACROSS NORTHERN CALIFORNIA. THEREFORE, OPTED FOR A
NON-NAM/UKMET BLEND FOR THIS SYSTEM.
...BINARY INTERACTION OF CLOSED LOWS THURSDAY-SATURDAY FROM THE
PLAINS INTO THE OH VALLEY...
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~~
PREFERENCE: 12Z NAM/UKMET/ECMWF, 00Z ECENS
CONFIDENCE: SLIGHTLY BELOW AVERAGE
MANY DETAILS STILL NEED TO BE IRONED OUT WITH TWO MID-LEVEL
IMPULSES MOVING THROUGH THE PLAINS TODAY INTO THURSDAY, AND HOW
THEY WILL INTERACT THROUGH THE REST OF THE WEEK. MULTIPLE FEATURES
INTERACTING CREATE LOWER THAN USUAL CONFIDENCE, BUT THE LEADING
SHORTWAVE MOVING THROUGH THE NORTHERN ROCKIES SHOULD EVENTUALLY
BECOME DOMINANT AND INTENSE, ESPECIALLY LATE ON RIDAY NIGHT FROM
THE MISSOURI VALLEY AND INTO THE OHIO VALLEY. THIS SHOULD LEAD TO
STRONG CYCLOGENESIS ALONG A TRIPLE POINT ACROSS THE MID-ATLANTIC
BY SATURDAY, WITH THIS TRIPLE POINT EXTENDING FROM A PRIMARY
SURFACE LOW BENEATH THE TRAILING UPPER TROUGH OVER THE UPPER
MIDWEST. MOISTURE DRAWN NORTHWARD AHEAD OF THIS SYSTEM COULD BE
SIGNIFICANT. WHEN LOOKING AT THE GUIDANCE, IT APPEARS AS IF THE
GFS STRUGGLES TO HANDLE A SHORTWAVE DIVING SOUTH THROUGH THE
DAKOTAS LATE THURSDAY THROUGH FRIDAY. THIS WILL ULTIMATELY IMPACT
THE EVOLUTION OF THIS SYTEM AND HOW FAR NORTH THE MOISTURE GETS
PULLED NORTHWARD AND EVENTUALLY THE PROGRESSION OF THE SURFACE LOW
INTO THE MID-ATLANTIC REGION. IN ADDITION, THE GFS HAS LACKED RUN
TO RUN CONSISTENCY WHICH CERTIANLY HAS CONTRIBUTED TO LESS
CONFIDENCE IN THE MODEL. THEREFORE, THE NAM/ECMWF/ECENS/UKMET ARE
IN GOOD AGREEMENT THROUGH 60 HOURS, WITH THE CMC TOO QUICK WITH
THE MID-LEVEL SHORTWAVE/TROUGH AXIS.
MODEL TRENDS AT WWW.WPC.NCEP.NOAA.GOV/HTML/MODEL2.HTML
500 MB FORECASTS AT WWW.WPC.NCEP.NOAA.GOV/H5PREF/H5PREF.SHTML
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