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January 3-4 Storm Thread part II

rduwx

By rduwx,
in Southeastern States

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Lookout

Lookout

Posted
Posted 
Good discussion from wpc this morning. they took a non nam compromise but noted it's worth watching due the nature of the beast. 


MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1127 AM EST MON JAN 01 2018

VALID JAN 01/1200 UTC THRU JAN 05/0000 UTC

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

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

COMPACT S/W ENTERING MT DROPS INTO THE LOWER MS VALLEY EARLY WED
SPURS RAPID COASTAL CYCLOGENESIS FROM BAHAMAS LATE WED TO GULF OF
MAINE THRU 00Z FRI
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL BLEND THROUGH 03/12Z
            12Z GFS/00Z ECMWF THEREAFTER (REPS. GEFS/ECENS)
CONFIDENCE: SLIGHTLY ABOVE AVERAGE THROUGH 03/12Z
            SLIGHTLY BELOW AVERAGE AFTERWARD

GOES-WV MOSAIC DEPICT A FAIRLY BROAD WARM SPOT ASSOCIATED WITH
CORE OF S/W THAT DESCENDS ALONG THE ROCKIES INTO THE CENTRAL
PLAINS TO LOWER MS VALLEY AND NORTHERN GULF THROUGH WED BECOMING
THE LARGE BASE OF LARGE SCALE TROF AS UPSTREAM SHORTWAVE (SEE
SECTION BELOW) CATCHES UP AND INTERACTS WITH SOME PHASING. THROUGH
THIS TIME PERIOD THE SPREAD IS FAIRLY MILD AND A GENERAL MODEL
BLEND CAN BE SUPPORTED...HOWEVER THE SMALL DIFFERENCES IN
SHAPE/INTENSITY AND LOCATION (N-S) WITH RESPECT TO THIS
INTERACTION SHOW HAVE LARGE SENSITIVITY DIFFERENCES TOWARD THE END
RESULT OF THE EXPECTED COASTAL LOW THAT DEVELOPS LATE WED OVER THE
N BAHAMAS AND RACES NORTH.   SENSITIVITIES CAN BE TRACKED TO THREE
SMALLER DIFFERENCES:  1) LATITUDE WHEN REACHING THE BASE OF THE
LARGE SCALE TROF OVER THE NORTHEAST GULF   2) SPACING FROM THE
UPSTREAM S/W  AND 3) MESOSCALE OR CONVECTIVE UPSCALE ENHANCEMENT
MAGNITUDE IN LATENT HEAT RELEASE TOWARD JET/OUTFLOW STRENGTH.

THE 12Z NAM ALONG WITH THE GFS ARE NORTH WITH THE INITIAL S/W
SHOWS EARLIER CONVECTIVE RESPONSE BUT MORE IMPORTANTLY GREATER
CONVECTIVE/FRONTOGENETIC RESPONSE DUE TO DEEPER COLD AIR AND
PROXIMITY TO WARMER GULF STREAM.  THIS COMBINATION SHIFTS THE
CYCLONE TO DEVELOP IN TWO CENTERS NEAR THE GA/SC GULF STREAM AS
WELL AS NORTH AND WEST OF THE MAIN CLUSTERING SEEN IN ENSEMBLE SFC
LOW CLUSTERS...EVENTUALLY THIS IMBALANCE IN A DUAL VORT/CENTER
STRUCTURE LEAS IT TO BE A DEEPER AND CLOSER TO THE COAST ALSO
DELAYING ITS NORTHWARD TREK AS A CLEAR OUTLIER.  WHILE NOT
PREFERRED DUE TO THIS OUTLIER NATURE; IT CAN BE DISMISSED AT THIS
POINT BUT GIVEN FINER RESOLUTION IN HORIZONTAL/VERTICAL IT IS
POSSIBLE IT MAY HAVE BETTER HANDLING OF COLD AIR/WARM GULF STREAM
PROCESSES THAN THE COARSER RESOLUTION GUIDANCE AND BEARS WATCHING
OVER SUBSEQUENT RUNS.

THE 00Z CMC IS FURTHEST SOUTH IN LATITUDE ROUNDING THE BASE OF THE
TROF BUT HAS MOST REDUCED INTERACTION WITH THE UPSTREAM S/W
LEADING TO A FASTER ACCELERATION TOWARD THE SARGASSO SEA.  AS SUCH
THE SURFACE CYCLONE DEEPS ON THE NORTHERN PERIPHERY OF THE
ENSEMBLE SUITE EVEN OUT PACING THE GFS/GEFS MEMBERS THAT DEVELOP
THE LOW FURTHER NORTH TO START WITH.  GIVEN THESE NEGATIVE ASPECTS
WILL NOT INCLUDE IN THE PREFERENCE AT THIS TIME.

THE 00Z UKMET WHILE A SOUTHERN REPRESENTATION HAS THE GREATEST
UPSTREAM S/W INTERACTION IN FACT SHOWING A MORE BINARY INTERACTION
WITH THE WAVE THAN A MORE PHASED/NEGATIVE TILTED ORIENTATION THAT
IS THE DOMINANT THREAT IN THE ENSEMBLE SUITE.  THIS ORIENTATION
SUPPORTS A DEEPER/RAPID BOMBING OF THE SURFACE CYCLONE WITH THE
MOST SIGNIFICANT 'UPPER CUT' SFC LOW TRACK THAT ARCS BACK TOWARD
NEW ENGLAND BY 00Z FRI.  AS SUCH THIS ALSO LOOKS TO BE A EXTREME
POTENTIAL LIKE THE NAM OR CMC. 

THE GFS LIKE THE NAM IS A NORTHERN LATITUDE REPRESENTATIVE BUT
WITH THE 12Z RUN SHOWS AN INCREASE IN SPACING BETWEEN THE UPSTREAM
WAVE ALLOWING FOR SLIGHTLY NORTH AND FASTER SURFACE
CYCLOGENESIS...YET STILL NOT AS FAST AS THE CMC.  THE 12Z RUN DOES
KEEP GOOD CONSISTENCY WITH PRIOR RUNS AND GEFS MEMBERS WHICH SHOW
THE MOST LINEAR SFC LOW TRACK PARALLELING THE COAST WITH VERY
LITTLE WESTWARD SHIFT TOWARD LATE THUR/FRI TO AFFECT NEW ENGLAND
LESS.

THE 00Z ECMWF IS ALSO CONSISTENT RUN TO RUN NOW BUT UNLIKE THE GFS
IS A SOUTHERN REPRESENTATIVE WITH SIMILAR SPACING/INTERACTION WITH
THE UPSTREAM WAVE.  THE FURTHER SOUTH SFC LOW DEVELOPMENT LIKELY
HAS A BIT MORE LATENT HEAT RELEASE/CONVECTIVE INFLUENCES ALLOWING
FOR A DEEPER LOW BY FRIDAY THAT TURNS LEFT (CURVED TRACK) RELATIVE
TO THE GFS. 

ALL IN ALL...THERE IS HIGH SENSITIVITY TO SMALL SCALE INTERACTIONS
AND PLACEMENT OF LATENT HEAT RELEASE IN THE SYSTEM TO HAVE HIGH
CONFIDENCE IN PICKING ONE SOLUTION OVER ANOTHER. ENSEMBLE
SUITE/SENSITIVITY TRACKS WOULD SUPPORT SOMETHING BETWEEN THE 00Z
ECMWF AND 12Z GFS POSSIBLY A 06Z GFS RUN MAY BE A BETTER BLEND
THAN 12Z GFS...BUT EITHER WAY BOTH REPRESENT THE CENTER OF THE
ENSEMBLE SUITE TO SELECT THEM AS WPC PREFERENCE AT THIS TIME. 
WHILE OVERALL CONFIDENCE IS BELOW AVERAGE...IT IS ONLY SLIGHTLY
GIVEN THE CLUSTERING (MINUS THE NAM) IS ACTUALLY NOT BAD 3 DAYS
OUT WITH SUCH A DYNAMIC/THERMODYNAMIC SETUP.
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Wow

Wow

Posted
Posted
6 minutes ago, Queencitywx said:

15/20 gets QPF back to 77 on the GEM.

Yep, was just checking them out.  Furthest west member brings the 1mm line to AVL and 25mm line to GSO.  Very Jan 2000-ish

The MEAN brings the 1mm past CLT @60hrs.  Impressive.

9SZsBdK.png

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griteater

griteater

Posted
Posted
48 minutes ago, packbacker said:

My guess is he is talking about the PV low over the lakes...not the chaser.  The chaser definitely phases and definitely helps the southern piece go neutral/neg, hour 42.  At 66 you see the PV low drop down, that will not phase, if it did then yes, it would 93 redux.

Yep...makes sense what he says...in the NAM runs you see the PV low (NS) kick out the southern h5 low, which is why the heaver QPF never really makes it to central NC.

Yes, there is definitely phasing that occurs with the 2 shortwaves over the southeast.  Quicker and stronger are the keys to getting precip back inland.  HM is talking about the 3rd shortwave dropping later through the Ohio Valley. 

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