758
FXUS10 KWNH 300501
PMDHMD
MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1200 AM EST THU JAN 30 2020
VALID JAN 30/0000 UTC THRU FEB 02/1200 UTC
...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR
INGEST...
00Z MODEL EVALUATION WITH PRELIMINARY PREFERENCES AND CONFIDENCE
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
...PRIMARY MID-LEVEL TROUGH OVER THE FOUR CORNERS NOW, CROSSING
SOUTH TEXAS THURSDAY AND THE SOUTHEAST FRIDAY...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: BLEND OF 29/12Z ECMWF/UKMET WITH SOME 29/12Z CMC AND
30/00Z GFS
CONFIDENCE: AVERAGE
A LEADING SHORTWAVE TROUGH OFF A RIDGE OVER THE INTERIOR PACIFIC
NORTHWEST EARLY THIS EVENING WILL SWING ACROSS NORTHERN MEXICO
THROUGH THURSDAY THEN SOUTH TEXAS ON THURSDAY NIGHT. A SECONDARY
TROUGH DIGS IN BEHIND THURSDAY NIGHT, WEAKENING THE MID-LEVEL
ENERGY AS IT CROSSES THE SOUTHEAST FRIDAY. THE 30/00Z NAM HAD
DECENT RUN TO RUN CONSISTENCY, BUT THAT LEFT THE NAM ON THE SLOWER
SIDE OF THE ENVELOPE OF SOLUTIONS.
...NORTHERN PORTION SECONDARY MID-LEVEL TROUGH CROSSING THE
CENTRAL PLAINS THURSDAY NIGHT/FRIDAY AND PUSHING OFF THE SOUTHEAST
COAST SATURDAY...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: BLEND OF 29/12Z ECMWF/UKMET WITH 30/00Z NAM
CONFIDENCE: BELOW AVERAGE
COMPLEX INTERACTION OF SEVERAL STREAMS LEAD TO A BELOW AVERAGE
CONFIDENCE FORECAST FROM THURSDAY NIGHT THROUGH SATURDAY. ONE
SHORTWAVE CROSSING THE INTERIOR PAC NW RIDGE THAT BREAKS OFF LATE
THURSDAY OVER THE NORTHERN PLAINS AND INTERACTS WITH A TROUGH OVER
THE GREAT LAKES FRIDAY INTO SATURDAY. HOWEVER, THERE IS DECENT
AGREEMENT THAT THE RESULTING TROUGH PUSHES OFF THE SOUTHEAST COAST
AND STAYS OFFSHORE AS IT LIFTS NORTH SATURDAY NIGHT/SUNDAY. THE
LATEST RUNS SHOW A SPLIT BETWEEN THE NCEP MODELS AND THE NON NCEP
MODELS WITH REGARDS TO THE FORMATION (OR NOT) OF A CLOSED LOW THAT
DROPS INTO THE SOUTHEASTERN U.S. AS SHOWN BY THE NCEP CAMP OR A
BROAD, DEEP AND FAIRLY UNIFIED FLOW PATTERN BY THE NON-NCEP.
INITIALLY, THOUGHT THE 30/00Z GFS DEEPENED THE LOW TOO MUCH AND
BROUGHT IT WELL TOO FAR SOUTH BY SATURDAY MORNING TO BE
USABLE...BUT THE 30/00Z NAM MADE A MOVEMENT TOWARDS THE GFS IDEA.
FOR THE MOMENT, WILL GIVE THE NOD TO THE 30/00Z NAM DUE TO ITS
SOMEWHAT WEAKER IDEA AND LESS INTERACTION WITH SHORTWAVE ENERGY
COMING IN FROM THE OHIO/TENNESSEE VALLEY BY SATURDAY AFTERNOON.
OVERALL, THINK THAT THE NCEP GUIDANCE SHOWING SOME SOUTHERN STREAM
MID LEVEL VORT/LOW MAKES SENSE GIVEN THE PRESENCE OF A 120 TO 140
KT UPPER LEVEL JET ACROSS THE GULF...BUT THE USING SOME
COMBINATION OF THE 29/12Z ECMWF AND THE 30/00Z NAM COULD YIELD A
REASONABLE COMPROMISE SOLUTION.
...LONGWAVE TROUGH APPROACHING THE WEST COAST OF CANADA FRIDAY
NIGHT/SATURDAY AND DOWNSTREAM ATMOSPHERIC RIVER INTO THE PACIFIC
NORTHWEST LATE THURSDAY INTO SATURDAY...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 29/12Z ECMWF/UKMET/ECENS BLEND WITH SOME 30/00Z NAM
CONFIDENCE: AVERAGE
THE PASSAGE OF A SHORTWAVE AND ACCOMPANYING COLD FRONT INTO
BRITISH COLUMBIA ON THURSDAY WILL BRING INITIALLY ZONAL FLOW INTO
WESTERN CANADA THAT AMPLIFIES AS RIDGING INCREASES AHEAD OF AN
UPSTREAM SHORTWAVE FRIDAY. GIVEN REASONABLY GOOD RUN-TO-RUN
CONSISTENCY IN THE 30/00Z NCEP GUIDANCE, DETERMINISTIC CONSENSUS
AND ENSEMBLES CONTINUE TO FAVOR A 29/12Z ECMWF/UKMET AND 30/00Z
NAM FOR THE TROUGH POSITION AND THE DOWNSTREAM ATMOSPHERIC RIVER
MOVING INTO THE PACIFIC NORTHWEST.
MODEL TRENDS AT WWW.WPC.NCEP.NOAA.GOV/HTML/MODEL2.HTML
500 MB FORECASTS AT WWW.WPC.NCEP.NOAA.GOV/H5PREF/H5PREF.SHTML
BANN
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