127
FXUS10 KWNH 250518
PMDHMD
MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1218 AM EST TUE FEB 25 2020
VALID FEB 25/0000 UTC THRU FEB 28/1200 UTC
...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR
INGEST...
00Z NAM/GFS EVALUATION INCLUDING PRELIMINARY PREFERENCES AND
FORECAST CONFIDENCE
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
...CLOSED LOW AND ITS INTERACTION WITH AN UPSTREAM AMPLIFYING
NORTHERN STREAM WAVE ACROSS PLAINS/GREAT LAKES THROUGH TUESDAY...
...ASSOCIATED SURFACE LOW CROSSING THE MISSISSIPPI RIVER AND INTO
THE GREAT LAKES TUE/WED...
..DEVELOPING EAST COAST LOW WED NIGHT.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 00Z NAM, 12Z ECMWF, 12Z UKMET THROUGH 12Z/27
NON 12Z CMC BLEND FROM 12Z/27 TO 12Z/28
CONFIDENCE: AVERAGE
A COMPLEX INTERACTION OF SEVERAL MID-LEVEL VORTICITY MAXIMA WILL
EVOLVE INTO A BROAD TROUGH COVERING THE EASTERN 2/3 OF THE NATION
BY THURSDAY MORNING. THE MAIN FEATURE OF INTEREST WILL BE A
SHORTWAVE WHICH IS CURRENTLY DIVING SOUTH THROUGH THE HIGH PLAINS
AND IS FORECAST TO REACH THE MISSISSIPPI RIVER VALLEY WEDNESDAY
MORNING. THE ENSEMBLES, WHICH HAD BEEN TRENDING FASTER THROUGH
SUNDAY'S RUNS HAVE REVERSED COURSE AND BEGIN TRENDING SLOWER AGAIN
WITH THE SHORTWAVE TROUGH AXIS OVER THE MIDDLE MISSISSIPPI RIVER
VALLEY WEDNESDAY MORNING. THE GOOD NEWS IS THAT THE SPREAD AMONG
ALL OF THE ENSEMBLE MEMBERS HAS BEEN DECREASING AND CONFIDENCE HAS
INCREASED TO NEAR AVERAGE FOR THIS SYSTEM.
THE 00Z GFS CONTINUES TO LOOK TOO FAST WITH THE AFOREMENTIONED
SHORTWAVE AND IS ALSO THE STRONGEST WITH THE LOW LEVEL LOW THROUGH
WEDNESDAY EVENING. THE 12Z CMC BECOMES THE SLOWEST BY WEDNESDAY
EVENING LEAVING THE 00Z NAM, 12Z ECMWF AND 12Z UKMET AS A
REASONABLE COMPROMISE.
BY THURSDAY INTO FRIDAY, AS THE PARENT SURFACE LOW TRACKS INTO
ONTARIO AND QUEBEC, SECONDARY LOW DEVELOPMENT IS EXPECTED ALONG
THE COAST OF MAINE. THERE IS REASONABLE AGREEMENT AMONG THE MOST
RECENT DETERMINISTIC GUIDANCE WITH THE SECONDARY LOW, ALTHOUGH THE
00Z NAM IS ON THE WEAKER SIDE, 00Z GFS A BIT NORTH OF THE ENSEMBLE
CLUSTER OF LOWS, AND 12Z UKMET A BIT STRONGER. HOWEVER, THE 12Z
CMC IS SLOWER AND MUCH DEEPER WITH THE SECONDARY LOW ALONG THE
COAST OF MAINE. THERE IS LESS SUPPORT FOR THE 12Z CMC SOLUTION AND
GIVEN ITS 500 MB LOW DIFFERS SIGNIFICANTLY WEST OF THE BETTER
CONSENSUS THURSDAY EVENING, THE 12Z CMC IS NOT PREFERRED. THIS IS
DUE TO A DIFFERING INTERACTION ALOFT WITH A SHORTWAVE DROPPING
SOUTH ACROSS THE UPPER GREAT LAKES WHICH AFFECTS THE CLOSED LOW
POSITION AT 500 MB IN THE CMC.
THEREFORE, BY THURSDAY INTO FRIDAY, A NON 12Z CMC BLEND IS
PREFERRED AS THE 00Z GFS MOVES INTO BETTER AGREEMENT WITH THE
REMAINING DETERMINISTIC AND ENSEMBLE GUIDANCE.
..REMAINDER OF THE CONUS
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL BLEND
CONFIDENCE: AVERAGE
THE REMAINDER OF THE LOWER 48 IS EXPECTED TO BE FAIRLY QUIET
THROUGH FRIDAY MORNING AS A +1 TO +1.5 STANDARDIZED HEIGHT ANOMALY
AT 500 MB REMAINS SITUATED ALONG THE WEST COAST. A NUMBER OF FAST
MOVING SHORTWAVES WILL MOVING ACROSS BRITISH COLUMBIA AND DIVE
SOUTHEASTWARD INTO THE GREAT PLAINS. THESE FEATURES ARE FAIRLY LOW
AMPLITUDE AS THE CROSS THE RIDGE AND THE LATEST MODELS ARE IN FAIR
AGREEMENT.
MODEL TRENDS AT WWW.WPC.NCEP.NOAA.GOV/HTML/MODEL2.SHTML
500 MB FORECASTS AT WWW.WPC.NCEP.NOAA.GOV/H5PREF/H5PREF.SHTML
OTTO
CLICK HERE TO GO TO PREVIOUS BULLETINS.
Main Text Page