Prognostic Meteorological Discussion
Issued by NWS

Current Version | Previous Version | Text Only | Print | Product List | Glossary Off
Versions: 1 2 3 4 5 6 7 8

000
FXUS10 KWNH 221646
PMDHMD

MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1246 PM EDT MON SEP 22 2014

VALID SEP 22/1200 UTC THRU SEP 26/0000 UTC

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

...AN EVALUATION OF THE 12Z NAM/GFS ALONG WITH PRELIMINARY
PREFERENCES/FORECAST CONFIDENCE...

THERE DID NOT APPEAR TO BE ANY INITIALIZATION ERRORS WITH THE 12Z
NAM/GFS DEEMED SIGNIFICANT ENOUGH TO IMPACT THEIR FORECASTS.


...NORTHERN STREAM TROF EXITING NEW ENGLAND ON TUESDAY...

PRELIMINARY PREFERENCE: GENERAL MODEL COMPROMISE
FORECAST CONFIDENCE: ABOVE AVERAGE

A NEGATIVELY-TILTED TROF IS FORECAST TO CONTINUE LIFTING NORTH AND
EAST THIS EVENING WITH ADDITIONAL SHORTWAVES TRACKING THROUGH
UPPER NEW ENGLAND. ONLY SMALL DIFFERENCES ARE NOTED AMONG THE
AVAILABLE MODELS SO A GENERAL MODEL COMPROMISE WOULD BE BEST
SUITED WITH THIS SECTOR OF THE CONUS.


...UPPER LOW CUTTING OFF OVER THE CAROLINAS...
...INVERTED TROF ALONG THE EASTERN SEABOARD...

PRELIMINARY PREFERENCE: 12Z NAM
FORECAST CONFIDENCE: LOW

WATER VAPOR IMAGERY SHOWED A POTENT SHORTWAVE DIVING INTO THE DEEP
SOUTH WITH A WELL DEFINED TONGUE OF DRY AIR SPILLING IN BEHIND IT.
BY 23/1200Z...THERE IS A CLEAR SIGNAL IN THE MODELS THAT THE
SYSTEM WILL NEARLY STALL AS IT BECOMES CUT OFF FROM THE NORTHERN
STREAM. BY TUESDAY EVENING...THE 00Z CMC IS THE FIRST TO LIFT THE
SHEARING ENERGY TOWARD THE COASTAL CAROLINAS ALTHOUGH IT DOES
EVENTUALLY WRAP VORTICITY BACK TOWARD THE EAST COAST SHORTLY
AFTERWARD. THE FORECAST BECOMES MORE NEBULOUS BY MID-WEEK ONWARD
AS THE SYSTEM CONTINUES TO SHEAR WITH VORTICITY CENTERS LIFTING
NORTHWARD ALONG THE EAST COAST. THE 00Z ECMWF/CMC FAVOR KEEPING
THE SHEAR AXIS FARTHER WEST WHICH FAVORS BRINGING HEAVY
PRECIPITATION INLAND. LOOKING AT THE SURFACE...STRONG
NORTHEASTERLY FLOW IS DEPICTED IN ALL GUIDANCE AS A STRONG SURFACE
HIGH BUILDS JUST OFFSHORE OF NEW ENGLAND. THE 12Z NAM SEEMS TO
AGREE WITH THE ENSEMBLE MEANS THROUGH DAY 2 WITH THE POSITION OF
THE INVERTED TROF ALONG THE COAST. THE 00Z ECMWF/CMC WERE SLIGHTLY
INLAND WHILE THE 12Z GFS/00Z UKMET WERE OFF TOWARD THE EAST. THIS
CONTINUES TO BE THE CASE INTO DAY 3 AS WELL. OVERALL...THE
SOLUTIONS DIFFER GREATLY FROM ONE ANOTHER WITH CONFIDENCE RATHER
LOW. FEEL THE 12Z NAM PRESENTS THE MOST CONSERVATIVE SOLUTION AND
SEEMS TO FIT SOMEWHERE IN BETWEEN THE MORE WESTERN 00Z ECMWF/CMC
AND EASTERN 12Z GFS.


...SLOW-MOVING UPPER TROF MOVING FROM THE CENTRAL GREAT BASIN TO
UPPER MIDWEST...

PRELIMINARY PREFERENCE: MODEL COMPROMISE BETWEEN THE 12Z NAM AND
00Z ECMWF/UKMET
FORECAST CONFIDENCE: AVERAGE

AN ELONGATED AXIS OF ENERGY IS EXPECTED TO SLIDE FROM THE CENTRAL
GREAT BASIN TOWARD THE NORTH-CENTRAL STATES DURING THE NEXT 24 TO
36 HOURS. THROUGH 24/0000Z...THE MODELS ARE REASONABLY CLUSTERED
WITH ONE ANOTHER. BY WEDNESDAY EVENING...THE 12Z GFS GETS AHEAD OF
THIS CONSOLIDATED SOLUTION AND CONTINUES PUSHING THIS ENERGY
EASTWARD ALONG THE SOUTHERN FRINGE OF THE WESTERLIES. ENSEMBLES
SUPPORT STALLING THE SYSTEM AND ALLOWING SHORTWAVE ENERGY TO
SLOWLY MIGRATE SOUTHWARD. THE 12Z GFS/00Z CMC DIVERGE MOST
SIGNIFICANTLY FROM THIS IDEA WHILE THE 12Z NAM AND 00Z ECMWF/UKMET
AT LEAST DO FAVOR THE CUT-OFF SOLUTION TO VARYING DEGREES. WPC
WILL FAVOR SOME SORT OF COMPROMISE BETWEEN THIS TRIO OF MODELS.


...WEAK AXIS OF VORTICITY LINGERING OVER THE SOUTHERN HIGH
PLAINS...

PRELIMINARY PREFERENCE: MODEL COMPROMISE BETWEEN THE 12Z NAM AND
00Z ECMWF/UKMET
FORECAST CONFIDENCE: AVERAGE

MODELS CONTINUE TO ADVERTISE A WEAKNESS IN THE MID-LEVEL FLOW
ACROSS THE SOUTHERN/CENTRAL PLAINS BY WEDNESDAY/THURSDAY. PLAN ON
STAYING CLOSER TO THE SOLUTION USED WITH THE ENERGY DRIFTING FROM
THE NORTHERN TIER TOWARD THE CENTRAL PLAINS GIVEN THE POTENTIAL
INTERACTION BETWEEN THE TWO. FOR INSTANCE...THE 12Z GFS/00Z CMC
WERE ALSO EAST OF THE SUGGESTED MODEL COMPROMISE ACROSS THE
SOUTHERN PLAINS. THE PREFERENCE WILL ALSO BE SOME SORT OF MODEL
COMPROMISE BETWEEN THE 12Z NAM AND 00Z ECMWF/UKMET.


...FULL-LATITUDE TROF ALONG THE IMMEDIATE WEST COAST BY THURSDAY...

PRELIMINARY PREFERENCE: BLEND OF THE 06Z GEFS/00Z ECMWF ENSEMBLE
MEANS
FORECAST CONFIDENCE: AVERAGE

THE PATTERN BECOMES QUITE AMPLIFIED ACROSS THE EASTERN PACIFIC AND
WESTERN U.S. WITH A RIDGE ANCHORING THE DESERT SOUTHWEST UP INTO
THE GREAT BASIN/ROCKIES. MEANWHILE...MORE IMPRESSIVELY...THE
UPSTREAM TROF CONTAINS 500-MB HEIGHT ANOMALIES OF 3 TO 3.5
STANDARD DEVIATIONS BELOW CLIMATOLOGY. THROUGH 25/0000Z...THE
ENSEMBLE MEANS ARE IN NEAR AGREEMENT WITH ONE ANOTHER WITH
SUFFICIENT SUPPORT FROM THE 00Z ECMWF/UKMET. THEREAFTER...THE
SPREAD IS SMALL WITH THE LEAD ENERGY ADVANCING TOWARD THE WESTERN
U.S. BUT MORE UNCERTAINTY LOOMS UPSTREAM WITH THE REMAINDER OF THE
TROF AXIS. MOST OF THESE DIFFERENCES ARE NOTED IN THE 564-DM
HEIGHT CONTOUR VIA SPAGHETTI PLOTS WITH MORE AGREEMENT NOTED AT
576-DM. THE 00Z ECMWF ENSEMBLE MEMBERS SHOW MORE AMPLIFICATION
THAN MANY OF THE OTHER SOLUTIONS. THE ENSEMBLE MEANS ARE FAIRLY
STEADY WITH THE LOCATION OF THIS TROF SO WILL LEAN ON THEIR
PROJECTION OF THIS SYSTEM WITH A DETERMINISTIC MODEL POTENTIALLY
ADDED TO THE MIX DURING THE NEXT ISSUANCE IF MORE AGREEMENT IS
SEEN.



...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

$$





USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.