578
FXUS10 KWNH 120426
PMDHMD
MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1225 AM EDT SAT OCT 12 2019
VALID OCT 12/0000 UTC THRU OCT 15/1200 UTC
...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR
INGEST...
00Z INITIAL MODEL EVALUATION WITH LATEST PREFERENCES AND CONFIDENCE
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
SUBTROPICAL STORM MELISSA
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL BLEND
CONFIDENCE: ABOVE AVERAGE
SUBTROPICAL STORM MELISSA IS NOW BEGINNING TO ACCELERATE TOWARDS
THE EAST-NORTHEAST AFTER REMAINING NEARLY STATIONARY WELL TO THE
SOUTH OF CAPE COD, MASSACHUSETTS. THE UPPER LEVEL RIDGE THAT HAD
BLOCKED THE STORM IS NOW MOVING OUT OF THE WAY AND THE LARGE SCALE
CIRCULATION AROUND THE UPPER MIDWEST LOW IS INCREASING THE
STEERING FLOW AND CAUSING IT TO GAIN FORWARD SPEED. SIMILAR TO
THE 12Z GUIDANCE ON FRIDAY, THE LATEST GUIDANCE SHOWS GOOD
AGREEMENT WITH THE EVOLUTION AND TIMING OF THIS SYSTEM AND THUS A
GENERAL MODEL BLEND IS PREFERRED.
DEEP PLAINS/UPPER MIDWEST CYCLONE
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL BLEND THROUGH SUNDAY NIGHT, THEN
GFS/ECMWF
CONFIDENCE: ABOVE AVERAGE
AN IMPRESSIVE DEEP LAYER CYCLONE OVER THE NORTH-CENTRAL U.S. HAS
REACHED MAXIMUM INTENSITY AS OF FRIDAY NIGHT, AND IS NOW FORECAST
TO GRADUALLY WEAKEN AFTER REMAINING NEARLY STATIONARY ON SATURDAY.
IT SHOULD THEN TRACK IN A GENERAL EASTWARD DIRECTION ACROSS LAKE
SUPERIOR AND THEN NORTHEASTWARD ACROSS ONTARIO. THE COLD FRONT
TRAILING FROM THE PARENT SURFACE LOW WILL CROSS THE APPALACHIANS
SATURDAY MORNING AND THEN EXIT THE EAST COAST BY SATURDAY NIGHT,
ALBEIT NOT NEARLY AS STRONG AS IT WAS OVER THE PLAINS. A
SECONDARY COLD FRONT ASSOCIATED WITH THE STORM SYSTEM WILL LIKELY
DEVELOP AND CROSS THE MIDWEST ON SUNDAY AND THEN MOVE TOWARD THE
EAST COAST ON MONDAY. THE MODELS REMAIN WELL CLUSTERED WITH THE
MASS FIELD EVOLUTION OF THIS SYSTEM THROUGH SUNDAY NIGHT. BY
MONDAY MORNING, THE 12Z CMC HAS ITS CLOSED LOW AND MID LEVEL
HEIGHT FIELDS SLIGHTLY FARTHER SOUTH THAN THE OTHER MODELS AS THE
ENERGY CROSSES INTO SOUTHEAST CANADA. THEREFORE, A GENERAL MODEL
BLEND IS BEST THROUGH 60 HOURS, FOLLOWED BY A GFS/ECMWF BLEND.
PACIFIC NORTHWEST TO THE NORTHERN PLAINS
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: NAM/GFS/ECMWF
CONFIDENCE: ABOVE AVERAGE
THE NEXT FEATURE OF INTEREST TO AFFECT THE WESTERN U.S. WILL BE A
PROGRESSIVE UPPER-LEVEL TROUGH AND ASSOCIATED COLD FRONT THAT
SHOULD REACH THE WEST COAST BY EARLY SUNDAY, AND THEN ADVANCE
INLAND ACROSS THE NORTHERN ROCKIES ON MONDAY. BY MONDAY NIGHT,
THE HEIGHT FALLS START ARRIVING ACROSS THE HIGH PLAINS AND INDUCES
LEE-SIDE CYCLOGENESIS OVER THE CENTRAL PLAINS TO UPPER MIDWEST.
THE MAIN DIFFERENCE NOTED WITH THE MODELS IS THAT THE 12Z UKMET IS
LESS AMPLIFIED THAN THE MODEL CONSENSUS WITH THE 500MB HEIGHTS,
AND IS SLOWER WITH THE FRONT THAT DEVELOPS ACROSS THE PLAINS.
THERE IS ENOUGH AGREEMENT AMONG THE NAM, GFS, AND ECMWF TO MERIT A
BLEND OF THESE MODELS.
SOUTHWESTERN U.S.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: ECMWF/UKMET/EC MEAN
CONFIDENCE: NEAR AVERAGE
A SOUTHERN STREAM SHORTWAVE PERTURBATION IS PROGGED TO REACH
CALIFORNIA SUNDAY NIGHT AND SEPARATES FROM THE NORTHERN STREAM
TROUGH MENTIONED ABOVE. THE CMC APPEARS SLIGHTLY MORE AMPLIFIED
IN THE MID TO UPPER LEVELS AND THE GFS BECOMES FASTER AS THE
SYSTEM CROSSES THE DESERT SOUTHWEST BY MONDAY. THE ECMWF AND
UKMET APPEAR TO FIT THE PATTERN BEST AND HAVE SUPPORT FROM THE EC
MEAN.
MODEL TRENDS AT WWW.WPC.NOAA.GOV/HTML/MODEL2.HTML
500 MB FORECASTS AT WWW.WPC.NOAA.GOV/H5PREF/H5PREF.SHTML
HAMRICK
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