Prognostic Meteorological Discussion
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FXUS10 KWNH 291624
PMDHMD
MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1223 PM EDT THU JUN 29 2017

VALID JUN 29/1200 UTC THRU JUL 03/0000 UTC

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

12Z MODEL EVALUATION INCLUDING PREFERENCES AND FORECAST CONFIDENCE
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

WEAKENING MID LEVEL TROUGH OVER THE WESTERN GULF...WHICH LIFTS
ACROSS THE CENTRAL GULF COAST THU/FRI
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 12Z GFS AND 00Z ECMWF/UKMET
CONFIDENCE: SLIGHTLY ABOVE AVERAGE

GOES-WV MOSAIC DENOTES LEAD SHORTWAVE LIFTING THROUGH THE CENTRAL
GULF/SOUTHEAST WITH A TRAILING TROF/WEAK TWIST ALONG THE NE TX
COAST.  THERE IS FAIRLY GOOD TIMING/SHAPE/EVOLUTION TO THE LEAD
SHORTWAVE EXITING THE CENTRAL GULF TOWARD THE CAROLINAS BY LATE
FRI...WITH EXCEPTION OF THE YESTERDAY`S 12Z CMC WHICH CONTINUES TO
REMAIN CONSOLIDATED WITH ONLY ONE DEEPER WAVE (FAVORING THE TX
COAST AXIS)...THE 00Z CMC TRENDED MUCH WEAKER BUT    THE UKMET
SHOWS SOME FASTER ACCELERATION WITH THE LEAD HEIGHT FALL/VORT
CENTER AND HAS AS STRONGER REPRESENTATION TO THE TRAILING FEATURE
THROUGH GA LATE FRIDAY BUT IS FAIRLY CLOSE TO THE ECWMF
REPRESENTATION.  THE 12Z NAM TRENDED BETTER IN TIMING AND SHAPE
BUT DUE TO NORTHERN STREAM (UNREALISTIC/UNFAVORABLE) INFLUENCES
DEFLECTING THE WAVE FURTHER NORTH TOWARD VA/NC...IT MAY NOT BE
EFFECTIVE IN THE BLEND PARTICULARLY AFTER THURSDAY NIGHT ALONG THE
EAST COAST.  THE 12Z GFS SHOWS GOOD CONTINUITY WITH PRIOR RUNS.
AS SUCH WILL SUPPORT A 12Z GFS AND 00Z ECMWF/UKMET BLEND AT
SLIGHTLY ABOVE AVERAGE CONFIDENCE.


SHORT WAVE/SURFACE LOW MOVES ACROSS THE UPPER GREAT LAKES
THU...THEN DISSIPATES ACROSS ONT/QUE FRI
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: NON-NAM BLEND
CONFIDENCE: SLIGHTLY ABOVE AVERAGE

GOES-WV LOOP SHOWS MAIN WAVE OVER UP OF MI ATTM WITH ELONGATION OF
THE S/W TROF SHEARING THROUGH LK HURON TOWARD N NEW ENGLAND LATER
TODAY...THOUGH TRENDS CONTINUE TO FAVOR EVENTUAL
WEAKENING/SHEARING OUT OF THE WAVE AND ITS SURFACE REFLECTION
ACROSS ONT/QUE BY FRI.  AS THE WAVE IS BREAKING DOWN THE
INFLUENCES OF THE UPSTREAM MEAN TROF WILL LEAD TO PROBLEMS IN
TIMING OF WEAKENING AS WELL AS PLACEMENT OF THE LOW.  THE 12Z NAM
HAVING A BIT OF DEEPER REPRESENTATION TO THE WAVE AS WELL AS
FASTER/STRONGER UPSTREAM SHORTWAVE FEATURES...EVENTUALLY SHIFTS
FOCUS TO THE UPSTREAM WAVE AND BREAKS FROM BETTER CONSENSUS OF THE
REMAINING GUIDANCE/ENSEMBLE SUITE EARLY FRIDAY.  THE 12Z GFS IS
ALSO A BIT LEFT/SLOWER THAN THE ECMWF/CMC SOLUTIONS THOUGH NOT
SIGNIFICANTLY TO REMOVE IT.  GIVEN IT WAS FIRST TO THE SLOWER/LEFT
TRACK TREND...THE FASTER/EASTWARD PRESENTATION OF THE UKMET WOULD
BE THE LOWER WEIGHTED GUIDANCE WITHIN A NON-NAM PREFERENCE.  GIVEN
SPREAD IS RELATIVELY SMALL CONFIDENCE REMAINS SLIGHTLY ABOVE
AVERAGE.


MID LEVEL LOW CROSSING THE NORTHERN PLAINS THU/FRI INTO GREAT
LAKES FRI/SAT/SUN
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 12Z GFS/00Z ECMWF
CONFIDENCE: AVERAGE

COMPLEX EVOLUTION WITH MULTIPLE COMPACT SHORTWAVE/MID-LEVEL CLOSED
LOWS WITHIN THE MEAN TROF ACROSS THE CENTRAL CONTINENT...POTENT
TROF CURRENTLY CROSSING THE NORTHERN US ROCKIES WITH VORT CENTER
NEAR THE BLACK HILLS WILL SWING THROUGH THE NORTHERN PLAINS
TONIGHT/TOMORROW FURTHER AMPLIFYING OVER THE GREAT LAKES FRI INTO
SAT...WITH DEEPENING SURFACE REFLECTION INTO NE ONT.  OVERALL THE
ENSEMBLES APPEAR TO BE LATCHING ONTO A MUCH TIGHTER AGREEMENT AND
SOLUTION.  THE 12Z GFS SHOWS LITTLE CHANGES FROM PRIOR OVERALL TO
THE EVOLUTION JUST A BIT FAST PARTICULARLY BY DAY 3 THAN THE
ECMWF/ECENS MEAN THOUGH ON THE SLOWER SIDE OF THE 06Z GEFS PACKET.
 THE 00Z UKMET CONTINUES TO TRACK SIMILAR WITH THE SHORTWAVES BUT
AS THE TROF ROUNDS THE SE PERIPHERY OF THE LARGER SCALE MEAN TROF
AXIS IN THE GREAT LAKES IT RAPIDLY DEEPENS THE LOW.  WHILE THIS
COULD BE BENEFICIAL TO A PROVIDING CONFIDENCE IN THE
TIMING/PLACEMENT IT IS TOO MUCH TO INCLUDE IN A PREFERENCE
PARTICULARLY AS THE GFS/ECMWF ARE IN MUCH BETTER ALIGNMENT
OVERALL.  THE 00Z CMC NEARLY MATCHES THE TIMING/PLACEMENT OF THE
ECMWF/ECENS MEAN JUST A BIT WEAKER.   THE 12Z NAM IS A CLEAR
OUTLIER...ALMOST 180 DEGREES OUT OF PHASE WITH THE TROF/RIDGES DUE
TO FASTER/DEEPER SOLUTION OF THE WAVE IN THE BLACK HILLS...AND
SHOULD BE FULLY AVOIDED. THE 09Z SREF IS MORE IN LINE WITH THE 06Z
GEFS...WHILE LESS FAVORABLE IN TIMING BEING TOO FAST.  AS SUCH
WILL FAVOR A 12Z GFS/00Z ECMWF BLEND TO REPRESENT THE OVERALL
ENSEMBLE MEAN...THOUGH CONFIDENCE IS ONLY AVERAGE EVEN THOUGH THE
AGREEMENT IS STRONG BETWEEN THE GFS/ECMWF MAINLY DRIVEN BY THE
CONTINGENCIES OF INTERACTION BETWEEN THE MAIN FEATURES AS WELL AS
CONVECTIVE INFLUENCE UPSCALE.


PHASING SHORTWAVES OVER EASTERN PACIFIC FRIDAY ADVANCE ASHORE
AFFECTING THE NW US ROCKIES TO S CA SAT/SUN
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: NON-UKMET BLEND
CONFIDENCE: SLIGHTLY ABOVE AVERAGE

STRONG MID-LEVEL RIDGE OFF THE CA WEST COAST IS PUMPING
SUBTROPICAL FLOW NORTHWARD ALONG 140W ALONG WITH SE PORTION OF
SHORTWAVE TROF IN NORTHERN STREAM AT THE NOSE OF THE WESTERLY
POLAR JET...THIS CONFLUENCE/PHASING OF FEATURES WILL SHIFT
EASTWARD COMING ASHORE IN SW OR/N CA BY LATE FRIDAY INTO SAT
MORNING.  WEAKENING NORTHERLY INFLUENCES/RIDGING OVER THE NORTHERN
ROCKIES AND WESTWARD RETROGRADE OF THE SUB-TROPICAL RIDGE OF S CA
WILL ALLOW FOR N-S SHEARING OF THE TROF SAT INTO SUN...LEADING TO
AN ELONGATED WEAKNESS FROM THE WESTERN ROCKIES TOWARD S CA BY 00Z
MON.  WHILE THE HEIGHT FIELDS SHOW DIFFERENCES THE ACTUAL HEIGHT
DIFFERENCES SEEM SMALL OVERALL AS THE SHORTWAVE FEATURE IS WELL
AGREED UPON WITH THE NAM/GFS/ECMWF/CMC.  ONLY THE 00Z UKMET FAVORS
A STRONGER SOUTHERN PORTION TO THE WAVE ALLOWING FOR A
DEEPENING/CONSOLIDATING WAVE TO MANIFEST (DECOUPLING THE
NORTHERN/SOUTHERN STREAM FEATURES.  WHILE POSSIBLE...THE BETTER
AGREEMENT/ENSEMBLE CONTINUITY SUGGESTS A NON-UKMET BLEND IS BEST
SUPPORTED.  CONFIDENCE IS SLIGHTLY ABOVE AVERAGE.


DEEP LAYERED LARGE SCALE CLOSED LOW CLIPPING PACIFIC NORTHWEST
LATE SUN
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: NON-CMC BLEND
CONFIDENCE: SLIGHTLY ABOVE AVERAGE

DEEP UPPER LOW OVER GULF OF AK WILL SHIFT EASTWARD BY THE END OF
THE WEEKEND...WITH A PERIPHERAL SHORTWAVE TROF ROTATING THROUGH
THE SE BASE OF THE TROF LATE SUNDAY DIRECTING CONFLUENT SWLY FLOW
IN ADVANCE OF WEAK SURFACE FRONT.  ONLY THE 00Z CMC SEEMS OUT OF
PHASE WITH A BIT MORE AMPLIFICATION UPSTREAM DIRECTING INCREASED
SWLY FLOW BY SUNDAY WHILE THE REMAINING GUIDANCE HAS FLATTENED
MORE WESTERLY BY SAID TIME.  AS SUCH A NON-CMC BLEND IS SUGGESTED
FOR THIS FEATURE AT SLIGHTLY ABOVE AVERAGE CONFIDENCE.


WWW.WPC.NCEP.NOAA.GOV/HTML/MODEL2.SHTML... /ALL LOWER CASE/
WWW.WPC.NCEP.NOAA.GOV/H5PREF/H5PREF.SHTML... /ALL LOWER CASE/

GALLINA

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