764
FXUS10 KWNH 250643
PMDHMD
MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
142 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 MODEL EVALUATION INCLUDING FINAL 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: NON 00Z CMC BLEND
CONFIDENCE: AVERAGE
..07Z UPDATE
RUN TO RUN CONSISTENCY CONTINUES TO BE BELOW AVERAGE FOR THE
DETERMINISTIC GUIDANCE WITH THE 00Z ECMWF/UKMET/CMC CYCLES
TRENDING SLIGHTLY FASTER AT 500 MB WITH THE MAIN SHORTWAVE
TRACKING FROM THE MISSISSIPPI RIVER VALLEY WEDNESDAY MORNING AND
INTO THE NORTHEAST AS A NEGATIVELY TITLED FEATURE THURSDAY MORNING.
GIVEN SOME OF THE RECENT CHANGES IN THE 00Z GUIDANCE, THE 00Z NAM
APPEARS SLIGHTLY SLOWER. HOWEVER, THE DIFFERENCES ARE SMALL ENOUGH
AND GIVEN SOME OF THE RUN TO FUN DIFFERENCES, A GENERAL MODEL
BLEND IS PREFERRED TO COME UP WITH AN AVERAGE MIDDLE GROUND. THE
ONE EXCEPTION IS WITH THE 00Z CMC WHICH CONTINUES TO DIFFER FROM
THURSDAY INTO FRIDAY WITH THE UPSTREAM SHORTWAVE OVER THE UPPER
GREAT LAKES IN THAT THE 00Z CMC SHOWS GREATER SEPARATION BETWEEN
TWO 850 MB LOW CENTERS WITH THE SECONDARY LOW TO THE EAST
DISPLACED EASTWARD, WHILE THE PRIMARY LOW IS DISPLACED WESTWARD OF
THE REMAINING MODEL CONSENSUS.
..PREVIOUS DISCUSSION FOLLOWS
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
..07Z UPDATE
NO SIGNIFICANT CHANGES WERE NOTED ACROSS THE REMAINDER OF THE
LOWER 48 REGARDING THE 00Z CMC/UKMET/ECMWF COMPARED TO THEIR
PREVIOUS 12Z CYCLES.
..PREVIOUS DISCUSSION FOLLOWS
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