Prognostic Meteorological Discussion
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754
FXUS10 KWNH 091925
PMDHMD

MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
224 PM EST TUE FEB 09 2016

VALID FEB 09/1200 UTC THRU FEB 13/0000 UTC

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

12Z GUIDANCE EVALUATION INCLUDING FINAL MODEL PREFERENCE AND
FORECAST CONFIDENCE
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

LONGWAVE TROF ACROSS THE EASTERN THIRD OF THE U.S LIFTING OUT BY
WED
ASSOCIATED SURFACE LOWS OVER THE E GREAT LAKES/THE MID-ATLANTIC
COAST TUESDAY/WEAK LOW S OF LONG ISLAND WED MORNING
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: OPERATIONAL MODEL CONSENSUS
CONFIDENCE: AVERAGE

MODELS REMAIN IN PRETTY GOOD AGREEMENT WITH THE TROUGH AS IT
BEGINS TO FILL AND LIFT TO THE NORTH. THE SURFACE LOW CURRENTLY
FAR OFF THE MID ATLANTIC COAST WILL MOVE NORTHEAST AND STAY WELL
SOUTHEAST OF NEW ENGLAND. HOWEVER WILL HAVE TO WATCH FOR POTENTIAL
WEAK LOW DEVELOPMENT BEHIND THIS LOW AS ADDITIONAL SHORTWAVE
ENERGY MOVES FROM NJ TO SOUTH OF LONG ISLAND ON WEDNESDAY.
ENSEMBLE LOW PLOTS SHOW EVEN MORE SPREAD IN THE 0Z GUIDANCE THAN
YESTERDAYS 12Z RUNS WITH THIS SYSTEM...KEEPING IT A LOW CONFIDENCE
FORECAST. THERE IS MORE SUPPORT IN THE 0Z ENSEMBLES FOR THE
POTENTIAL OF A SLIGHTLY STRONGER AND FURTHER WEST LOW...WHICH
WOULD HAVE SNOW IMPACTS FOR LONG ISLAND INTO SOUTEHRN NEW ENGLAND.
THE NEW 12Z GFS HAS JOINED THE STRONGER/WEST GROUP TO JOIN THE GEM
AND UKMET. THIS SEEMS TO TRACE BACK TO THE STRENGTH OF THE SUBTLE
SHORTWAVE ENERGY AS IT EXITS THE COAST EARLY WEDNESDAY. HOWEVER A
COMPARISON OF THE 06Z AND 12Z GFS SHOWS VERY SIMILAR INITIAL
CONDITIONS WITH THIS WAVE...WITH DIFFERENCES NOT REALLY APPEARING
UNTIL 12Z-18Z WEDNESDAY. THUS APPEARS MORE LIKELY TO BE MORE OF
THE INNER DYNAMICS/PHYSICS WITHIN THE MODEL RESPONSIBLE FOR THE
CHANGE. OVERALL THIS ASPECT OF THIS TROUGH REMAINS LOW
CONFIDENCE...WITH THE ECMWF REMAINING WEAKER AND EAST AND THE NAM
KIND OF IN BETWEEN. HARD TO IGNORE THE RECENT TREND TOWARDS THE
STRONGER/WEST/WETTER SOLUTIONS. FOR NOW WILL PREFER A GENERAL
MODEL CONSENSUS SOLUTION...AS CAN NOT COMPLETELY RULE OUT THE
FURTHER EAST SOLUTIONS SUCH AS THE ECMWF AND OLDER GFS RUNS. THE
12Z UKMET APPEARS TOO FAR WEST...BUT CLOSE ENOUGH TO BE INCLUDED
IN ANY BLEND AT THIS TIME.

AGAIN WHILE MODELS ARE IN GOOD AGREEMENT ON THE LARGER SCALE
EVOLUTION...THERE ARE ALSO SOME DIFFERENCES WITH A POTENTIAL WEAK
LOW DEVELOPMENT OFF THE MAINE COAST...DUE TO DIFFERENCES IN THE
HANDLING OF SUBTLE SHORTWAVE FEATURES WITHIN THE TROUGH. LOWER
CONFIDENCE ON THESE DETAILS AND WILL CONTINUE TO JUST PREFER A
GENERAL CONSENSUS SOLUTION FOR NOW.

19Z UPDATE: NO CHANGE IN OUR PREFERENCE BASED ON 12Z
ECMWF/UKMET/GEM. ECMWF REMAINS WEAKER AND FURTHER OFFSHORE WITH
THE LOW AND THUS QPF. GIVEN THE SMALL SCALE DETAILS RESPONSIBLE
FOR THESE DIFFERENCES...A OPERATIONAL MODEL BLEND CONTINUES TO BE
PREFERRED.


ARCTIC CUT-OFF/COLD SURGE ENTERING THE NORTHERN GREAT
LAKES/ARROWHEAD OF MN FRI MORNING
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: OPERATIONAL MODEL CONSENSUS
CONFIDENCE: SLIGHTLY ABOVE AVERAGE

IN THE WAKE OF THE FILLING LARGE SCALE TROF ACROSS THE EASTERN
U.S...A STRONG WAVE DEEPENING ACROSS THE NORTH POLE WILL DROP
SOUTH AND DEEPEN THE ARCTIC VORTEX BUILDING A DEEP POOL OF ARCTIC
COLD ACROSS HUDSON BAY THURS AND JAMES BAY BY FRIDAY MORNING.
OVERALL THE MODELS ARE IN FAIRLY GOOD AGREEMENT WITH THE OVERALL
SETUP INVOLVING THIS ARCTIC UPPER LOW AND ARCTIC SURFACE HIGH
MOVING TOWARDS THE NORTHERN PLAINS. AS CAN BE EXPECTED THERE ARE
MINOR DETAIL DIFFERENCES IN BOTH THE POSITION AND DEPTH OF THE
LOW/TROUGH...BUT ALL AVAILABLE DETERMINISTIC GUIDANCE SEEMS WELL
WITHIN THE ENSEMBLE SPREAD FOR THIS SYSTEM. FOR THAT REASON WILL
CONTINUE TO FAVOR A GENERAL MODEL CONSENSUS SOLUTION.


WEAK WAVE AND LOW MOVING ACROSS THE NORTHERN/CENTRAL PLAINS INTO
THE MS VALLEY TUE/WED
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: OPERATIONAL MODEL CONSENSUS
CONFIDENCE: ABOVE AVERAGE

CONTINUE TO SEE GOOD AGREEMENT AMONG THE GUIDANCE WITH THE
SHORTWAVE DIVING SOUTHEAST INTO THE NORTHERN PLAINS ALONG THE
EASTERN EDGE OF THE PACIFIC RIDGE...AND THE ASSOCIATED SURFACE LOW
FORMING NEAR AN AREA OF STRONG LOW/MID LEVEL FRONTOGENESIS. THE 0Z
ECMWF REMAINS A BIT QUICKER THAN THE CONSENSUS...BUT IS CLOSE
ENOUGH TO THE OTHER GUIDANCE TO CONTINUE TO PREFER A GENERAL MODEL
CONSENSUS.


DEEPER LARGE SCALE TROF APPROACHING NORTHWEST LATE FRIDAY
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: NON GEM CONSENSUS
CONFIDENCE: SLIGHTLY ABOVE AVERAGE

WILL CONTINUE WITH THE NAM/GFS/ECMWF PREFERENCE. THE 0Z UKMET
REMAINS MORE ON THE OUTER EDGE OF THE ENSEMBLE SPREAD AND SEEMS TO
REPRESENT A LESS LIKELY SOLUTION...WITH PRETTY GOOD CONTINUITY
SEEN IN THE GEFS AND ECMWF ENSEMBLE MEMBERS. THE 0Z GEM IS CLOSER
TO THE BETTER ENSEMBLE CLUSTERING BUT STILL A BIT QUICKER WITH THE
WAVE AND ALSO WEAKER WITH WEST COAST RIDGE.

17Z UPDATE: 0Z UKMET HAS COME MORE IN LINE WITH THE TIMING OF THE
WAVE AND STRENGTH OF THE RIDGE. THE 0Z GEM IS ALSO NOW IN BETTER
AGREEMENT...ALTHOUGH IS NOW WEAKER WITH AN INITIAL SURGE OF ENERGY
AND FRONTAL BOUNDARY EARLIER FRIDAY THAN THE REMAINDER OF THE
GUIDANCE. THUS WILL CHANGE THE PREFERENCE TO A NON GEM CONSENSUS.


SHORTWAVE ENTERING PACIFIC NORTHWEST WEDNESDAY...DIVING SOUTHEAST
INTO THE BASE OF THE EAST COAST TROUGH INTO FRIDAY
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: NON NAM BLEND
CONFIDENCE: SLIGHTLY ABOVE AVERAGE

THE 12Z NAM AND OZ UKMET ARE A BIT FURTHER SOUTH WITH THIS WAVE
MOVING INTO THE PACIFIC NORTHWEST ON WEDNESDAY AND WEAKER/FLATTER
WITH THE WEST COAST RIDGE IT IS MOVING INTO. THIS ALLOWS THE WAVE
TO MORE QUICKLY ROUND THE TOP OF THE RIDGE...AND REMAIN A BIT
STRONGER AS IT THEN DIVES SOUTHEAST TOWARDS THE SOUTHEASTERN
PORTION OF THE COUNTRY BY FRIDAY. STILL SOME MINOR DIFFERENCES
WITHIN THE ECMWF/GFS/GEM SOLUTIONS...BUT THEY SEEM TO BE MORE
REPRESENTATIVE OF THE BETTER CLUSTERING AT THIS TIME.

17Z UPDATE: APPEARS TO BE A TREND IN THE 12Z GLOBAL GUIDANCE FOR A
SLIGHTLY FURTHER SOUTH SHORTWAVE TRACK INTO THE NORTHWEST AND A
WEAKER UPPER RIDGE. THIS ALLOWS THE WAVE TO DIVE SOUTHEAST A BIT
QUICKER INTO THE NORTHERN PLAINS WHILE ALSO MAINTAINING A BIT MORE
OF ITS STRENGTH. WOULD THUS NOW APPEAR THAT THE GFS IS A BIT OF A
WEAK OUTLIER WITH THIS SYSTEM AS IT TRACKS ACROSS THE CENTRAL
PORTION OF THE COUNTRY...ALTHOUGH THIS DOES NOT SEEM TO HAVE AN
IMPACT ON ITS EVENTUAL LOW DEVELOPMENT OFF THE SOUTHEAST COAST.
THE 12Z NAM IS NOW THE BIGGEST OUTLIER...WITH SLIGHT DIFFERENCES
IN THIS WAVE AND HOW IT TRACKS AROUND THE BASE OF THE NORTHEAST
UPPER LOW. NOT AN IMPOSSIBLE SOLUTION...BUT SEEMS LESS LIKELY AT
THIS TIME. THUS A NON NAM BLEND SEEMS LIKE A GOOD STARTING POINT.

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

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

CHENARD

$$





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