Prognostic Meteorological Discussion
Issued by NWS

Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9
000
FXUS10 KWNH 270653
PMDHMD

MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
152 AM EST TUE JAN 27 2015

VALID JAN 27/0000 UTC THRU JAN 30/1200 UTC

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

00Z MODEL EVALUATION WITH FINAL PREFERENCES
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
NAM/GFS INITIALIZATION ERRORS DO NOT SEEM TO DEGRADE THEIR SHORT
RANGE FORECASTS.


EVOLVING COASTAL STORM ALONG THE NORTHERN MID ATLANTIC/NORTHEAST
MON-WED
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 12Z EC MEAN OR A 2/3 00Z NAM...1/3 00Z ECMWF COMPROMISE
CONFIDENCE: AVERAGE

THE 12Z ECMWF WAS TOWARD THE EDGE OF THE ENSEMBLE SCATTER LOW
PLOTS CONSISTING OF 12Z ECMWF/GEFS/CMC MEMBERS BUT OVER ITS PAST 4
RUNS...THE DETERMINISTIC ECMWF HAS BEEN TRENDING IN THE DIRECTION
OF THE CENTROID OF ENSEMBLE MEMBERS INCLUDING THE MOST CURRENT 00Z
ECMWF. THE 00Z ECMWF ADJUSTED TOWARD THE FASTER CAMP EARLY IN THE
FORECAST PERIOD...BUT RESEMBLES THE NAM MORE CLOSELY THAN THE
OTHER DETERMINISTIC MODELS BY THE END OF DAY 1...12Z/28. THE
CENTROID CLUSTER OF ENSEMBLE MEMBERS IS BEST REPRESENTED BY THE
12Z EC MEAN OR A BLEND OF THE 00Z NAM AND 00Z ECMWF OR EVEN THE
21Z SREF WHICH ALSO APPEARS REASONABLE. THE FINAL PREFERENCE IS A
NUDGE TOWARD THE FASTER CAMP OF MODELS.

THE 00Z GFS/UKMET/CMC APPEAR TO BE SLIGHTLY FASTER THAN THE 18Z
GEFS AND 21Z SREF MEANS...SO WILL STICK WITH THE SLOWER EDGE OF
THE GUIDANCE. THIS PREFERENCE IS SUPPORTED BY SHORT TERM FORECASTS
MADE UP OF A CONSENSUS OF HI-RES MODEL GUIDANCE. TOWARD THE SLOWER
CAMP ALSO ALIGNS CONCEPTUALLY GIVEN THE ORIENTATION OF THE SYSTEM
ALOFT (NEGATIVE TILT) AND A SIGNIFICANT UPSTREAM RIDGE NOSING INTO
THE CANADIAN MARITIMES.

AS IS ALWAYS THE CASE WITH THESE BIG STORMS...EVEN SMALL DETAIL
DIFFERENCES RESULT IN LARGE IMPACT DIFFERENCES...ESPECIALLY WITH
PRECIPITATION. PREFERENCES LISTED HERE REFLECT MODEL POSITION AND
MASS FIELDS...BUT REFER TO WPC WINTER WEATHER AND QPF DESK
PRODUCTS FOR INFORMATION ON LIQUID EQUIVALENTS/SNOW.


WEAKENING CLOSED LOW MOVING INTO CALIFORNIA EARLY TUE
REMNANT SHORTWAVE PASSING THROUGH THE CENTRAL PLAINS WED AND THE
  OH VALLEY ON THU
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 00Z GFS/ECMWF/UKMET BLEND
CONFIDENCE: AVERAGE

THE MODELS HAVE CONVERGED TOWARD ONE ANOTHER THROUGH THU
MORNING...12Z/29...WITH SOME DIVERGENCE AFTERWARD. BEYOND
12Z/29...REGARDING AN UPPER TROUGH DIGGING TOWARD THE GREAT
LAKES...THE DEEPER UKMET GAINED SUPPORT FROM THE 00Z ECMWF/CMC BUT
THE CMC IS ON THE DEEPER SIDE OF THE GUIDANCE AT THIS POINT. THE
NAM IS WEAKER WITH ENERGY DROPPING SOUTH THROUGH THE UPPER
MISSISSIPPI VALLEY AND IN TURN...WINDS UP FASTER WITH THE
VORTICITY MAX MOVING THROUGH THE OHIO VALLEY. A GFS/ECMWF/UKMET
BLEND IS PREFERRED WITH THIS SYSTEM AND THE BEGINNING OF POTENTIAL
SECONDARY LOW DEVELOPMENT NEAR THE NEW ENGLAND COAST 12Z/30.


MID-LEVEL SHORTWAVE MOVING INTO BRITISH COLUMBIA EARLY TUE
SUBSEQUENT MOVEMENT INTO THE N-CENTRAL U.S./GREAT LAKES THU
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 00Z GFS/ECMWF/UKMET BLEND
CONFIDENCE: AVERAGE

SIMILAR TO THE ABOVE MENTIONED SYSTEM...THE GFS/ECMWF/UKMET/CMC
SHOW RELATIVELY GOOD AGREEMENT UNTIL LATE THU AT WHICH POINT THE
00Z CMC BECOMES MORE AMPLIFIED WITH THE UPPER TROUGH AMPLIFYING
ACROSS THE UPPER GREAT LAKES. THE GFS/ECMWF/UKMET SHOW GOOD
AGREEMENT WITH SUPPORT FROM THE ENSEMBLE MEANS...THOUGH THE
GFS/UKMET ARE SLIGHTLY FASTER THAN THE ECMWF.


UPPER TROUGH MOVING INTO THE SOUTHWEST TOWARD THE END OF THE WEEK
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 00Z GFS...12Z ECMWF BLEND
CONFIDENCE: AVERAGE

THERE IS RELATIVELY MINOR SPREAD IN A SOMEWHAT BROAD UPPER TROUGH
MAKING ITS WAY TOWARD THE WEST COAST. TRENDS SHOW NO REAL PUSH ONE
WAY OR ANOTHER...AND THE MIDDLE OF THE LATEST ENSEMBLE SPAGHETTI
HEIGHTS SUPPORTS A BLEND OF THE GFS/ECMWF...WHICH IS A COMPROMISE
BETWEEN THE FASTER AND SLOWER MODEL SOLUTIONS...OUTSIDE OF THE
WESTWARD/SLOWER 00Z NAM.


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

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

OTTO

$$




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