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FXUS10 KWNH 101728
PMDHMD

MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1228 PM EST WED FEB 10 2016

VALID FEB 10/1200 UTC THRU FEB 14/0000 UTC

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

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

LONGWAVE TROF LIFTING OUT OF THE EASTERN THIRD OF THE U.S WED/THU
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: OPERATIONAL MODEL BLEND
CONFIDENCE: ABOVE AVERAGE

GUIDANCE IS IN GOOD AGREEMENT WITH THE LIFTING TROUGH AND THE
ASSOCIATED PIECES OF SHORTWAVE ENERGY. AN OPERATIONAL MODEL BLEND
SHOULD HANDLE THIS SYSTEM WELL.


ARCTIC CUT-OFF/COLD SURGE ENTERING THE NORTHERN GREAT
LAKES/ARROWHEAD OF MN FRI MORNING AND ASSOCIATED SURFACE LOW
ACROSS SE ONTARIO/NEW ENGLAND SAT
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: OPERATIONAL MODEL BLEND
CONFIDENCE: 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. THE
MODELS REMAIN IN GOOD AGREEMENT WITH THE OVERALL SETUP INVOLVING
THIS ARCTIC UPPER LOW AND ARCTIC SURFACE HIGH MOVING TOWARDS THE
NORTHERN PLAINS. THE ECMWF AND MOST OF ITS ENSEMBLE MEMBERS HAVE
CONSISTENTLY BEEN DEEPER WITH THE TROUGH THAN THE OTHER GUIDANCE.
OVERALL THE DIFFERENCES ARE RELATIVELY MINOR...AND GIVEN THE
CONSISTENCY OF THE ECMWF AND ITS ENSEMBLES...CAN NOT COMPLETELY
RULE THAT OUT. THUS WILL PREFER A GENERAL OPERATIONAL MODEL BLEND
WHICH SHOULD MITIGATE THE DIFFERENCES.


SHORTWAVE ENTERING PACIFIC NORTHWEST WEDNESDAY RAPIDLY DIVING
SOUTHEAST INTO THE BASE OF THE EAST COAST TROF INTO FRI AND
OFFSHORE EARLY SAT
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: OPERATIONAL MODEL BLEND
CONFIDENCE: ABOVE AVERAGE

SHORTWAVE ENERGY FROM THE BASE OF A NEGATIVELY TILTED TROF WILL
GLANCE THE PACIFIC NORTHWEST ON WEDNESDAY. THE TREND HAS BEEN FOR
MORE ENERGY TO BE SHED INTO THE RIDGE...WHICH ALLOWS FOR A
SLIGHTLY STRONGER SYSTEM TO TRACK ACROSS THE COUNTRY...LEADING TO
A SURFACE LOW FORMATION OFF THE CAROLINA COAST ON FRIDAY. MODELS
ARE NOW IN VERY GOOD AGREEMENT WITH THIS SYSTEM. THE 12Z NAM MAY
BE A BIT TOO CLOSE TO THE COAST WITH THE EVENTUAL SURFACE LOW
FORMATION...BUT STILL SEEMS WITHIN THE RANGE OF PLAUSIBLE
SOLUTIONS AND THUS WILL REMAIN IN OUR PREFERRED BLEND FOR NOW.


DEEPER LARGE SCALE TROF APPROACHING NORTHWEST FRIDAY
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: NON UKMET CONSENSUS
CONFIDENCE: SLIGHTLY BELOW AVERAGE

TRENDS OVER THE PAST SEVERAL ENSEMBLE CYCLES HAVE BEEN FOR A LESS
AMPLIFIED PATTERN...WITH A WEAKER FLATTER TROUGH/RIDGE SETUP
ACROSS THE NORTHWEST TOWARDS THE END OF DAY 3. IT IS A COMPLEX
PATTERN...WITH MULTIPLE SHORTWAVES EMBEDDED WITHIN THE LARGE SCALE
TROUGH THAT APPROACHES THE WEST COAST. HAVE A LEADING VORTICITY
AXIS MOVING ASHORE FRIDAY ALONG WITH THE ASSOCIATED FRONTAL
BOUNDARY. THEN WILL HAVE A TRAILING SHORTWAVE QUICKLY ON ITS HEELS
MOVE ASHORE BY FRIDAY NIGHT.

THE UKMET HAS BEEN ON THE LEADING EDGE OF THE TREND FOR THE LESS
AMPLIFIED OVERALL PATTERN ACROSS THE NORTHWEST. HOWEVER IT IS THE
STRONGEST WITH THE TRAILING AREA OF VORTICITY AND CONTINUES TO LIE
ON THE SOUTEHRN/DEEPER EDGE OF THE GUIDANCE ENVELOPE WITH THIS
WAVE. AND RECENT TRENDS WITH THIS WAVE HAVE BEEN FOR A
WEAKER/FURTHER NORTH SOLUTION...AGAINST THE UKMET SOLUTION. THIS
EVENTUALLY ALLOWS THE UKMET TO DIG DEEPER WITH THE WAVE AND BECOME
OUT OF PHASE WITH THE OTHER DETERMINISTIC GUIDANCE BY LATER IN DAY
3 INTO THE MEDIUM RANGE. WHILE THIS CAN NOT COMPLETELY BE RULED
OUT...STILL APPEARS TO BE A LESS PROBABLE SOLUTION AND WILL
CONTINUE TO NOT BE PREFERRED.

OTHERWISE THE GFS/NAM ARE VERY SIMILAR...BEING SLOWER WITH THE
OVERALL PROGRESSION. THE 0Z ECMWF IS THE QUICKEST GUIDANCE...WITH
THE 0Z GEM IN BETWEEN. THE 0Z GEFS AND ECMWF MEANS SUGGEST THAT A
SOLUTION BETWEEN THE GFS/NAM AND ECMWF SOLUTIONS MAY BE MOST
LIKELY AT THIS TIME. THUS A CONSENSUS OF THESE SOLUTIONS MAY BE A
GOOD STARTING POINT FOR DEALING WITH THIS SYSTEM. SINCE THE GEM IS
ALSO CLOSE TO THESE SOLUTIONS IT CAN ALSO BE INCLUDED. STILL
ENOUGH SPREAD WITH THIS SYSTEM TO RESULT IN SLIGHTLY BELOW AVERAGE
CONFIDENCE.



...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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