Prognostic Meteorological Discussion
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000
FXUS10 KWNH 311857
PMDHMD

MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
156 PM EST SAT JAN 31 2015

VALID JAN 31/1200 UTC THRU FEB 04/0000 UTC

...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR
INGEST...

12Z MODEL EVALUATION...INCLUDING THE NAM/GFS/UKMET/GEM AND THE
ECMWF


...NEGATIVELY-TILTED TROF OVER NEW ENGLAND EARLY IN THE PERIOD...
...ASSOCIATED COASTAL LOW...

PREFERENCE: GENERAL MODEL COMPROMISE
CONFIDENCE: ABOVE AVERAGE

THE DEEP LOW CENTER OFFSHORE NORTHERN NEW ENGLAND WILL IS FORECAST
TO LIFT NORTHEAST THROUGH THE CANADIAN MARITIMES OVER THE NEXT DAY
OR SO. THE MODELS ARE REASONABLY WELL CLUSTERED WITH THE EXIT OF
THIS SYSTEM...AND SO A GENERAL MODEL COMPROMISE WILL BE FAVORED.


...CLOSED LOW MOVING FROM THE DESERT SOUTHWEST TOWARD
WESTERN/CENTRAL MEXICO...

PREFERENCE: NON-NAM CONSENSUS
CONFIDENCE: AVERAGE

THE MODELS SHOW THE ELONGATED N/S UPPER TROUGH AND ASSOCIATED
CLOSED LOW OVER THE SOUTHWEST GRADUALLY GETTING SUPPRESSED
SOUTHWARD OVER THE NEXT COUPLE OF DAYS. THE GUIDANCE SUGGESTS THE
UPPER LOW CENTER WILL SOUTH DOWN TO OVER THE BAJA PENINSULA
TONIGHT AND SUNDAY BEFORE THEN SHIFTING SLOWLY EAST TO MAINLAND
MEXICO LATER MONDAY AND TUESDAY. THE 12Z MODELS ARE NOW BETTER
CLUSTERED WITH THE POSITION OF THE CLOSED LOW BY THE END OF THE
PERIOD...ALTHOUGH THE 12Z NAM DOES HAVE ITS LOW CENTER DISPLACED A
BIT EAST OF THE GLOBAL MODEL CONSENSUS. A NON-NAM CONSENSUS WILL
BE THE PREFERENCE.


...AMPLIFYING TROUGH AND ASSOCIATED SURFACE LOW TRACKING FROM THE
MIDDLE MS VALLEY TO THE MID-ATLANTIC ON SUNDAY/MONDAY...

PREFERENCE: BLEND OF THE 12Z GFS/12Z ECMWF
CONFIDENCE: AVERAGE

A ROBUST SHORTWAVE IS SEEN IN GOES RGB/WV SAT IMAGERY DIGGING
SOUTHEAST ACROSS THE NORTHERN HIGH PLAINS...AND THIS ENERGY IS
EXPECTED TO FURTHER AMPLIFY OVER THE NEXT COUPLE OF DAYS AS IT
MOVE INTO THE MID MS VALLEY BY LATER SUNDAY AND THEN EAST ACROSS
THE OH VALLEY/MID-ATLANTIC AND SOUTHERN NEW ENGLAND THROUGH
MONDAY. THE HEIGHT FALLS WILL BE INSTRUMENTAL IN DEVELOPING
SURFACE LOW PRESSURE ALONG AN ARCTIC FRONTAL ZONE BY LATER TODAY
OVER THE LOWER MO VALLEY WHICH WILL THEN MOVE EAST AND TRACK
GENERALLY NEAR THE OH RIVER SUNDAY AND SUNDAY NIGHT. ON
MONDAY...THIS LOW WILL REDEVELOP EAST OF THE APPALACHIANS OVER THE
CENTRAL MID-ATLANTIC AND LIFT NORTHEAST JUST OFFSHORE SOUTHERN NEW
ENGLAND ON MONDAY.

THE 12Z NAM HAS TRENDED JUST A TAD WEAKER AND MORE SUPPRESSED WITH
ITS LOW TRACK COMPARED TO ITS 00Z RUN...AND SUGGESTS A LOW TRACK
JUST A TAD NORTH OF THE OH RIVER. CONVERSELY...THE 12Z GFS HAS
TRENDED SLOWER/DEEPER ALOFT AND THUS A BIT STRONGER WITH ITS
SURFACE LOW. THE 12Z UKMET WHICH RUN TO RUN FOR A COUPLE OF DAYS
NOW HAS BEEN ON THE STRONG SIDE OF THE MODEL SPREAD...IS ALSO
CLOSE TO THE 12Z GFS...ALTHOUGH THE UKMET IS GENERALLY A BIT NORTH
OF THE . THE GFS SOLUTION AFTER ABOUT 36 HOURS. THE GFS AND UKMET
IMPLY NOTABLY WARMER THERMAL PROFILES ACROSS THE OH
VALLEY/MID-ATLANTIC AND SOUTHERN NEW ENGLAND AS THEIR LOW TRACKS
ARE THE FARTHEST NORTH SOLUTIONS.

THE 12Z GEM IS A SLOWER AND MORE SUPPRESSED OUTLIER SOLUTION NOW
WITH THIS SYSTEM AND WILL BE DISMISSED. THE 12Z ECMWF HAS TRENDED
A LITTLE FARTHER NORTH/WARMER...AND IS JUST A LITTLE SLOWER AND
WEAKER THAN THE 12Z GFS. BY MON...THE 12Z NAM BECOMES THE
WEAKEST/FASTEST SOLUTION...WITH THE GEM THE SLOWEST. THE MULTI-DAY
TREND TREND IN THE GUIDANCE GOING BACK TO YESTERDAY CONTINUES TO
FAVOR A STRONGER AND WARMER SOLUTION FROM THE MID MS VALLEY EAST
ACROSS THE OH VALLEY AND ALSO NOW SOUTHERN NEW ENGLAND. BASED ON
THE LATEST TRENDS AND MODEL CLUSTERING...A BLEND OF THE 12Z GFS
AND 12Z ECMWF WILL BE PREFERRED THROUGHOUT THE EVENT.


...LOW-AMPLITUDE WAVES AFFECTING THE PACIFIC NORTHWEST EARLY NEXT
WEEK...

PREFERENCE: GENERAL MODEL COMPROMISE
CONFIDENCE: AVERAGE

AN UPPER RIDGE ANCHORING THE WESTERN U.S. BETWEEN 30 AND 40 N
LATITUDE WILL GRADUALLY BREAK DOWN AS A SERIES OF LOW-AMPLITUDE
IMPULSES TRACK ACROSS THE PACIFIC NORTHWEST LATE SUNDAY ONWARD.
OVERALL...THE MODELS ARE REASONABLY CLOSE TO ONE ANOTHER WITH THE
LARGER SCALE PATTERN. A GENERAL MODEL COMPROMISE WILL BE PREFERRED
TO RESOLVE ANY LARGER SCALE DIFFERENCES THAT EXIST.

...MODEL TREND GRAPHICS AT
www.wpc.ncep.noaa.gov/html/model2.shtml...

...500 MB FORECASTS AT
www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml...

ORRISON

$$





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