Prognostic Meteorological Discussion
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FXUS10 KWNH 210444
PMDHMD

MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1244 AM EDT TUE OCT 21 2014

VALID OCT 21/0000 UTC THRU OCT 24/1200 UTC

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

...AN EVALUATION OF THE 00Z NAM/GFS ALONG WITH PRELIMINARY
PREFERENCES/FORECAST CONFIDENCE...

THERE DID NOT APPEAR TO BE ANY INITIALIZATION ERRORS WITH THE 00Z
NAM/GFS DEEMED SIGNIFICANT ENOUGH TO IMPACT THEIR FORECASTS.


...SHEARING MID-LEVEL ENERGY OVER SOUTHERN NM/FAR WEST TX...

PRELIMINARY PREFERENCE: GENERAL MODEL CONSENSUS
FORECAST CONFIDENCE: HIGH

A BATCH OF VORTICITY SLIDING ACROSS NORTH-CENTRAL MX WILL CONTINUE
TO SHEAR AS IT NEARS THE RIO GRANDE. ALL MODELS AGREE ON THIS
OCCURRING DURING THE NEXT 12 TO 24 HOURS SO WILL RECOMMEND A
GENERAL MODEL CONSENSUS GIVEN THE AGREEMENT.


...SHORTWAVES CROSSING THE GREAT LAKES REGION EARLY ON...
...COASTAL STORM AFFECTING THE NORTHEASTERN U.S. COAST WEDNESDAY
THROUGH FRIDAY...

PRELIMINARY PREFERENCE: BLEND OF THE 00Z GFS/12Z ECMWF
FORECAST CONFIDENCE: SLIGHTLY BELOW AVERAGE

WATER VAPOR IMAGERY SHOWED A PAIR OF IMPULSES MOVING THROUGH THE
CENTRAL APPALACHIANS AND LOWER GREAT LAKES...RESPECTIVELY.
EVENTUALLY THE SYSTEM BECOMES BETTER ORGANIZED AS IT CLOSES ALOFT
FORMING A CLOSED LOW OVER THE MID-ATLANTIC BY TUESDAY EVENING.
THROUGH 36 HOURS/WEDNESDAY MORNING...MODELS SHOW SUFFICIENT
AGREEMENT BEFORE DIFFERENCES EMERGE WITH THE COASTAL DEVELOPMENT.
THE ENSEMBLE SURFACE LOW PLOT BY 22/1200Z SHOWS THE 12Z GEFS
MEMBERS BEING WEST OF THE 12Z ECMWF/CMC ENSEMBLE MEMBERS. THIS
SEPARATION HAS BEEN NOTED IN THE 3 OF THE PAST 4 PLOTS DATING BACK
TO MODELS RUN 36 HOURS AGO. HOWEVER...BY 23/0000Z...THE 12Z ECMWF
ENSEMBLE MEMBERS ARE CLOSER TO THE COAST. THROUGHOUT THE EVOLUTION
OF THIS COASTAL LOW...THE 18Z GEFS/21Z SREF/12Z ECMWF ENSEMBLE
MEANS ARE FAIRLY IN LINE WITH ANOTHER. THE 00Z GFS/12Z ECMWF
APPEAR TO FOLLOW THIS CONSOLIDATED SOLUTION MOST READILY. AT TIMES
THE 12Z UKMET APPEARED REASONABLE BUT THEN ALLOWS THE COASTAL LOW
TO LINGER NEAR LONG ISLAND MUCH LONGER. WILL SUGGEST A BLEND OF
THE 00Z GFS/12Z ECMWF WITH SOMEWHAT COMPROMISED CONFIDENCE.


...STRONG SHORTWAVE CURRENTLY MOVING INTO NORTHERN CA...
...EVENTUAL SPLIT FLOW OVER THE CENTRAL U.S. BY MID-WEEK....

PRELIMINARY PREFERENCE: THROUGH 23/1200Z: BLEND OF THE 00Z GFS/12Z
ECMWF...THEREAFTER: BLEND OF THE 18Z GEFS/12Z ECMWF ENSEMBLE MEANS
FORECAST CONFIDENCE: BELOW AVERAGE

A PRONOUNCED SHORTWAVE CURRENTLY PUSHING INTO NORTHERN CA WILL
QUICKLY LIFT NORTHEASTWARD TOWARD THE NORTHERN GREAT BASIN DURING
THE NEXT 24 HOURS. AGREEMENT IS MUCH BETTER THAN RECENT DAYS WHERE
SOME OF THE GUIDANCE TRIED TO ALLOW SHORTWAVE ENERGY TO SINK
SOUTHWARD TOWARD THE FOUR CORNERS REGION. THE FORECAST BECOMES
MORE UNCERTAIN THEREAFTER AS SOME OF THE MID-LEVEL VORTICITY LIFTS
INTO CENTRAL CANADA WHILE THE REMAINING ENERGY TRACKS ALONG THE
NORTHERN TIER MID-WEEK. THE 00Z NAM AND 12Z CMC/UKMET SHOW MORE OF
THE SYSTEM MIGRATING INTO MANITOBA WHICH LEAVES A WEAKER SYSTEM
ACROSS THE NORTHERN PLAINS. THIS LEAVES A RATHER MESSY FORECAST IN
PLACE FOR THE CENTRAL U.S. AND EVENTUALLY INTO THE MS RIVER
VALLEY. THE 576-DM SPAGHETTI PLOT SHOWS THE UNCERTAINTY QUITE WELL
WITH A SLEW OF SOLUTIONS PORTRAYED BY THE INDIVIDUAL ENSEMBLE
MEMBERS. THROUGH 60 HOURS/THURSDAY MORNING...WILL LEAN ON THE
CLUSTER OF THE 00Z GFS/12Z ECMWF WHICH SUPPORT A MORE ROBUST
SYSTEM IN THE NORTHERN TIER STATES. THEREAFTER...HAVE TO PUSH AWAY
FROM THE DETERMINISTIC MODELS GIVEN THE GROWING SPREAD AND UTILIZE
A 18Z GEFS/12Z ECMWF ENSEMBLE MEANS BLEND THROUGH 24/1200Z.


...BROAD CYCLONIC FLOW ACROSS THE NORTHEASTERN PACIFIC WEDNESDAY
THROUGH FRIDAY...

PRELIMINARY PREFERENCE: BLEND OF THE 18Z GEFS/12Z ECMWF ENSEMBLE
MEANS
FORECAST CONFIDENCE: BELOW AVERAGE

IN THE WAKE OF THE INITIAL SYSTEM MOVING INTO THE INTERMOUNTAIN
WEST...THE MID-LATITUDE FLOW SEE THE AMPLITUDE DECREASE AND BECOME
A BIT MORE ZONAL IN NATURE. WITH LOWER HEIGHTS CENTERED OVER THE
NORTHEASTERN PACIFIC....A MYRIAD OF PROGRESSIVE SHORTWAVES WILL
BOMBARD THE PACIFIC NORTHWEST WITH ENHANCED ONSHORE FLOW
ACCOMPANYING EACH WAVE. THE MODELS INITIALLY HAVE A DECENT HANDLE
ON THE PATTERN BEFORE UNCERTAINTY INCREASES. MORE
SPECIFICALLY...THE GUIDANCE BEGINS TO STRUGGLE WITH THE TIMING OF
THE NEXT ROUND OF HEIGHT FALLS APPROACHING THE NORTHWESTERN U.S.
LATE IN THE WORK WEEK. THE 552-DM SPAGHETTI PLOT SHOWS THE 12Z
GEFS MEMBERS BEING EAST OF THE SLOWER 12Z ECMWF ENSEMBLE MEMBERS.
THE SPREAD BETWEEN THESE TWO ENSEMBLE MEANS HAS DECREASED
RECENTLY...PARTICULARLY COMPARED TO THE 00Z MODEL CYCLE THE
PREVIOUS DAY. WILL SPLIT THE DIFFERENCE BETWEEN THESE TWO ENSEMBLE
MEANS FOR NOW.




...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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