Prognostic Meteorological Discussion
Issued by NWS

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6
000
FXUS10 KWNH 231704
PMDHMD

MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1200 PM EST THU FEB 23 2017

VALID FEB 23/1200 UTC THRU FEB 27/0000 UTC

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

12Z NAM/GFS MODEL EVALUATION INCLUDING PRELIMINARY PREFERENCES
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

...SOUTHERN STREAM CLOSED LOW FEATURE OVER S FL LIFTING
NE/WEAKENING OFF THE SOUTHEAST COAST THROUGH EARLY SAT...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL BLEND
CONFIDENCE: ABOVE AVERAGE

MODELS NOW IN GENERALLY GOOD ALIGNMENT WITH THE EVOLUTION OF THIS
FEATURE. THE 12Z NAM/GFS REMAIN SOLIDLY IN THE FAST/PROGRESSIVE
CAMP ALONG WITH THE 00Z UKMET...WITH THE 00Z CMC A BIT SLOWER WITH
RESPECT TO THE WAVE AND SURFACE LOW. 00Z ECMWF ALIGNS SIMILARLY
BUT IS A BIT FLATTER WITH THE UPPER WAVE. WILL MAINTAIN A GENERAL
MODEL BLEND WITH ABOVE AVERAGE CONFIDENCE.


...BROAD LONGWAVE TROF CROSSING THE INTERMOUNTAIN WEST THU/FRI
WITH DEVELOPING CLOSED LOW AND SURFACE LOW OVER MIDWEST LATE FRI
INTO SAT...AND THROUGH THE CENTRAL GREAT LAKES INTO ONTARIO BY
EARLY SUN...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: NON-CMC BLEND
CONFIDENCE: AVERAGE

LATEST IR/WV SAT IMAGERY SHOWING A BROAD LONG WAVE TROUGH ACROSS
THE WESTERN CONUS...WITH A WELL DEFINED UPPER SHORTWAVE DIVING
ACROSS THE CENTRAL GREAT BASIN. GOOD MODEL AGREEMENT EXISTS IN
LIFTING THIS LEAD SHORTWAVE ACROSS THE NORTH CENTRAL ROCKIES INTO
THE CENTRAL HIGH PLAINS THROUGH TONIGHT...EVENTUALLY CLOSING OFF
OVER THE MID MISSOURI VALLEY BY FRIDAY NIGHT. RESULTANT HEIGHT
FALLS WILL RESULT IN RAPID SURFACE CYCLOGENESIS ALONG THE FRONTAL
ZONE FROM E KS INTO E IA/IL AND THE WESTERN GREAT LAKES BY FRI
NIGHT. AS IS TYPICALLY THE CASE AT THIS TIME RANGE...THE 12Z NAM
CONTINUED ITS ABRUPT SHIFT TOWARD THE REMAINDER OF THE GUIDANCE
ENVELOPE...AND HAS LOCKED INTO LINE WITH THE MIDDLE OF THE ROAD
ECMWF/GFS/GEFS CAMP. THE 00Z CMC REMAINS THE ONLY STRONG OUTLIER
AT THIS STAGE...AND ONCE AGAIN TRENDS FROM THE 06Z NAEFS MAY
PORTEND TO THE 12Z CMC CATCHING UP TO THE REST OF THE GUIDANCE
WITH RESPECT TO HANDLING OF THIS FEATURE. OVERALL...GIVEN GROWING
MODEL CONSENSUS AND WITH PREVIOUS MASS FIELD ISSUES LARGELY
RESOLVED...A NON-CMC BLEND IS PREFERRED. HOWEVER...FROM AN
OPERATIONAL PROSPECTIVE...WEIGHTING HEAVILY FAVORS THE MORE MIDDLE
GROUND SOLUTIONS OF THE ECMWF AND THE 12Z NAM...WHICH ALONG WITH
THE 12Z NAM PARALLEL IS QUICKLY COMING INTO GOOD ALIGNMENT. SINCE
FORECAST CONFIDENCE IS STEADILY GROWING...WILL CHARACTERIZE
FORECAST CONFIDENCE AS SLIGHTLY ABOVE AVERAGE.

PLEASE REFER TO WPC QPF QPFPFD AND WINTER WEATHER QPFHSD
DISCUSSIONS FOR ADDITIONAL DETAILS.


...PAIR OF SHORTWAVES DROPPING ALONG THE WESTERN CANADIAN COAST
TOWARD A MORE AMPLIFIED UPPER LOW OFF THE NORTHWEST COAST BY SAT...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 2/3 00Z ECMWF / 1/3 12Z GFS/NAM
CONFIDENCE: BELOW AVERAGE

WHILE SOME TIGHTENING HAS OCCURRED WITH THE NEW 12Z NAM...A
RELATIVELY LARGE SPREAD REMAINS AMONG DETERMINISTIC MODELS WITH
RESPECT TO HOW MUCH ENERGY IS SHEARED WEST TOWARD THE DEEP UPPER
LOW WELL NORTH OF HAWAII...WITH THE INITIAL WAVE THAT CAN BE SEEN
DARKENING IN WV IMAGERY JUST S OF 50N/140W. THE 12Z NAM/GFS...AS
WITH THE 00Z SUITE BEFORE IT...CONTINUES A TREND TOWARD A TIGHTER
PROXIMITY OF THE WAVES FRI THROUGH EARLY SAT. SO THERE ARE
POSITIVE TRENDS TOWARD MORE ENERGY GETTING INCORPORATED WEST
TOWARD THE DEEPENING LOW NEAR HAWAII. THIS MANIFESTS IN ALLOWING
THE UPPER LOW WEST OF VANCOUVER ISLAND BC AT MIDDAY TODAY TO DIG
SOUTH ALONG AND OFFSHORE OF THE PAC NW FRIDAY...TO THE N CA COAST
SATURDAY. THE 12Z NAM HAS TRENDED TOWARD THE 00Z ECMWF/UKMET CAMP
WITH A SOLUTION THAT FAVORS LAGGING THIS ENERGY A BIT. THE RESULT
IS A MORE VIGOROUS/CONCENTRIC VORTICITY MAXIMA WITH THE DIGGING
LOW OFF THE CA COAST OVER THE WEEKEND. WILL NOT WEIGHT THE 00Z
UKMET AT THIS TIME AS IT BECOMES AN OUTLIER LATE IN THE
PERIOD...COMPLETE WITH A SHARP WESTWARD SHIFT OF THE DIGGING LOW
BY 00Z/SUN. FOR ITS PART...THE 12Z GFS DID TREND TOWARD THE ECMWF
CAMP...BUT IT REMAINS ON THE FAST END OF THE GUIDANCE ENVELOPE BY
THE END OF THE PERIOD...DIGGING THE UPPER LOW INTO THE DESERT
SOUTHWEST BY SUNDAY. FOR OPERATIONAL UTILITY...A BLEND OF THE
ECMWF/NAM/GFS (WEIGHTED IN THAT ORDER) IS PROBABLY SUFFICIENT...AS
SPREAD AMONG GEFS/ECENS MEMBERS WILL WASH OUT THE STRONGER CLOSED
LOW SOLUTIONS DEPICTED BY EACH OF THE DETERMINISTIC MODELS.
HOWEVER...GIVEN CONTINUED ISSUES W/SIGNIFICANT RUN TO RUN
VARIABILITY...FORECAST CONFIDENCE REMAINS LOWER THAN AVERAGE.

...NEXT SHORTWAVE DROPPING OUT OF COASTAL BC TO NW WA COAST BY
SUN...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL BLEND
CONFIDENCE: SLIGHTLY ABOVE AVERAGE

THE TRAIN OF FAST MOVING BUT STRONG SHORTWAVES CONTINUES INTO THE
END OF THE PERIOD...WITH MODELS CONTINUING TO DEPICT SHORTWAVE
ENERGY PUSHING OVER TOP THE STRONG ANTICYCLONE DOMINATING THE GULF
OF ALASKA...ACROSS THE PACIFIC NORTHWEST SUN/SUN NIGHT.
CONSIDERING TIMING ISSUES WITH THE AMPLIFYING UPPER LOW ABOVE...IT
IS SURPRISING THAT MODELS ARE IN REASONABLY GOOD ACCORD WITH THIS
NEXT SHORTWAVE DROPPING ACROSS THE PAC NW SUN/SUN NIGHT. THE 12Z
GFS HAS TRENDED A BIT MORE TOWARDS THE DEEPER ECMWF SOLUTION . THE
00Z UKMET REMAINS MOST WOUND UP BUT HAS SLOWED SLIGHTLY AND IS A
BIT WEST OF THE MAIN CLUSTER OF SOLUTIONS. THE 00Z CMC IS A DECENT
MIDDLE OF THE ROAD SOLUTION BY SUNDAY NIGHT...IN BETWEEN THE
FASTER GFS AND SLOWER ECMWF. HOWEVER...GIVEN THAT IT IS DAY
3...DIFFERENCES ARE RELATIVELY MINOR WITH MASS FIELDS REASONABLY
WELL RESOLVED. WILL KEEP A GENERAL MODEL BLEND WEIGHTED TOWARD THE
ECMWF AND 12Z GFS AT ABOVE AVERAGE CONFIDENCE.

www.wpc.ncep.noaa.gov/html/model2.shtml...

www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml...

MONTEFUSCO

$$





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