Prognostic Meteorological Discussion
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000
FXUS10 KWNH 311646
PMDHMD

MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1145 AM 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 AND GFS


...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: BLEND OF THE 12Z GFS AND 00Z ECMWF
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 NAM/12Z GFS AND 00Z GEM
SHIFT THE CLOSED LOW A LITTLE FARTHER EAST INTO MEXICO BY TUESDAY
VERSUS THE 00Z ECMWF AND 00Z UKMET. THE LATEST GEFS AND ECENS MEAN
GENERALLY SUPPORT THEIR DETERMINISTIC COUNTERPARTS...SO WILL
COMPROMISE WITH A BLEND OF THE GFS AND ECMWF.


...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/00Z ECMWF...THROUGH 48 HOURS
            BLEND OF THE 12Z GFS/00Z GEM...48 HOURS TO 84 HOURS

CONFIDENCE: SLIGHTLY BELOW 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 ONLY MODEL AS STRONG AS THE 12Z GFS IS THE 00Z
UKMET WHICH RUN TO RUN FOR A COUPLE OF DAYS NOW HAS BEEN ON THE
STRONG SIDE OF THE MODEL SPREAD. THE GFS AND UKMET IMPLY NOTABLY
WARMER THERMAL PROFILES ACROSS THE OH VALLEY/MID-ATLANTIC AND
SOUTHERN NEW ENGLAND AS THEIR LOW TRACKS ARE A BIT FARTHER
NORTH...ESPECIALLY ACROSS THE UPPER OH VALLEY/MID-ATLANTIC AND
SOUTHERN NEW ENGLAND.

THROUGH ABOUT 48 HOURS...THE 00Z GEM IS THE MOST
SUPPRESSED...FOLLOWED BY THE 00Z ECMWF. THEREAFTER...THE 00Z ECMWF
BECOMES THE MOST SUPPRESSED SOLUTION AS THE OTHER MODELS TUCK
SURFACE LOW PRESSURE IN A LITTLE CLOSER TO SOUTHERN NEW
ENGLAND...WITH TRACKS THAT ARE NEAR OR EVEN A LITTLE LEFT OF THE
BENCHMARK. BY MON...THE 12Z NAM BECOMES THE FASTEST
SOLUTION...WITH THE UKMET 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. GIVEN THE
LINGERING SPREAD AND ENSEMBLE LOW SCATTER PLOTS...WE FEEL THAT A
COMPROMISE BETWEEN THE 12Z GFS AND 00Z ECMWF WILL WORK THROUGH 48
HOURS...FOLLOWED BY A 12Z GFS/12Z GEM BLEND THEREAFTER AS LOW
PRESSURE ADVANCES THROUGH THE MID-ATLANTIC AND NEAR SOUTHERN NEW
ENGLAND.


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

PREFERENCE: NON-UKMET CONSENSUS
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 WITH A TAD MORE VARIANCE NOTED WITH THE
INDIVIDUAL SHORTWAVES. THIS IS ESPECIALLY THE CASE WITH THE 00Z
UKMET WHICH IS A STRONGER OUTLIER WITH ENERGY CROSSING THE PACIFIC
NORTHWEST LATE MONDAY. WILL PREFER A NON-UKMET CONSENSUS AS A
RESULT.


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

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

RUBIN-OSTER

$$





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