Deep surface low will form off SE,mid-atlantic coast

[cycloneye]

MODEL DIAGNOSTIC DISCUSSION
NWS HYDROMETEOROLOGICAL PREDICTION CENTER CAMP SPRINGS MD
120 PM EDT MON OCT 18 2004

VALID OCT 18/1200 UTC THRU OCT 21/0000 UTC

MODEL INITIALIZATION...

SFC... NO INITIALIZATION ERRORS WITH THE 12Z ETA AND GFS.

500 MB... THE GFS IS BETTER INITIALIZED WITH THE SHORT WAVE IN
THE PLAINS THAN THE ETA. THE ETA IS TOO HIGH WITH HEIGHTS IN KS.
OVERALL THOUGH BOTH MODELS ARE INITIALIZED VERY WELL.

MOISTURE...
THE ETA AND GFS ARE WELL INITIALIZED WITH MOISTURE/PWS ACROSS
THE CONUS.


MODEL TRENDS...

ETA...
A COUPLE OF TRENDS WITH THE 12Z ETA WHEN COMPARED TO THE
00Z/18 ETA. THE FIRST INVOLVES THE CLOSED LOW UP IN THE
ATLANTIC PROVINCES. THE 12Z ETA IS MUCH SLOWER IN SLIDING THIS
FEATURE DOWNSTREAM FROM 36 TO 60 HRS AND ALLOWS THE
SURFACE HIGH BASED OVER QUEBEC TO REMAIN MORE PREVALENT
ACROSS THE NORTHEAST AND MID-ATL.

THE 12Z ETA IS ALSO DIGGING THE SHORT WAVE DYNAMICS AND
UPPER-LEVEL TROUGH OFF THE CENTRAL/SRN COAST FARTHER TO
THE SOUTHWEST FROM 36 HRS ON. THE RESULTANT IS THE BASE OF
THE UPPER-LEVEL TROUGH SWINGING TOWARD THE SRN CA COAST IS
SLOWER AND THIS ALLOWS HEIGHTS TO REMAIN HIGHER FROM THE
SOUTHWEST/SRN PLAINS NORTHWARD.

GFS...
THE 12Z GFS INDICATES ONE SIGNIFICANT TREND WHEN COMPARED TO
THE 00Z/18 GFS. THE SHORT WAVE MOVING OFF THE SOUTHEAST
COAST AROUND 42 TO 48 HRS IS DEEPER/STRONGER AND THE 12Z GFS
HOLDS ONTO THIS INTENSIFICATION THROUGH 60 HRS. AS A RESULT...
A DEEPER SURFACE LOW DEVELOPS OFF THE SOUTHEAST/MID-ATL
COAST.


MODEL DIFFERENCES AND PREFERENCES...

THE 12Z MODEL GUIDANCE SHOW TWO DIFFERENCES DURING THE
FCST PERIOD... ONE OUT WEST AND ANOTHER OFF THE MID-
ATL/SOUTHEAST COAST.

MID-ATL/SOUTHEAST... A GREAT DEAL OF UNCERTAINTY REVOLVES
AROUND THE UPPER-LEVEL SHORT WAVE ALONG THE SRN STREAM
THAT SLIDES THROUGH THE MID-ATL/SOUTHEAST AT 48 HRS AND OFF
THE COAST AT 60 HRS. THERE IS A BIG DIFFERENCE IN LOCATION AND
INTENSITY OF THIS LOW PRESSURE AREA BY 60 HRS. THE GFS IS THE
DEEPEST SOLUTION ALOFT AND AT THE SURFACE. THE GFS ALSO
APPEARS TO HAVE A GRID SCALE FEEDBACK SITUATION WITH THE 500
MB VORT AND POSSIBLY LEADS TO THE RAPID INTENSIFICATION OF THE
SURFACE LOW ALONG THE COAST. THE ETA IS IDENTICAL TO THE GFS
IN PLACEMENT OF THE SURFACE LOW AT 60 HRS BUT VERY DIFFERENT
WITH THE INTENSITY. THIS IS DUE TO A WEAKER SHORT WAVE SLIDING
UP INTO SOUTH CENTRAL CANADA AND A STRONGER HIGH PRESENCE
REMAINING IN PLACE ACROSS THE NORTHEAST AND EAST OF THE
APPALACHIANS. THE ETA DOES SHOW BETTER CONTINUITY WITH THIS
SYSTEM THAN THE GFS. THE CANADIAN LEANS MORE TOWARD THE ETA
AND THE UKMET IS SOMEWHAT A COMPROMISE BETWEEN THE ETA
AND GFS. HPC SUGGESTS LEANING TOWARD A COMPROMISE BETWEEN
THE ETA AND GFS ON INTENSITY OF THE SURFACE LOW.




The big question is if it will this low turn into a subtropical system down the road or it mantains as a cold core low.

[Wnghs2007]

Dont know. will be interesting to see

[yoda]

Hmm, we will see... but aren't SST's in this region marginal for even ST Dev.?

[Wnghs2007]

Hmm, we will see... but aren't SST's in this region marginal for even ST Dev.?

I believe so but I also believe that development is possible as long as upper level conditions are favorable.

[rainstorm]

gfs often has strong lows that dont actually appear

[yoda]

gfs often has strong lows that dont actually appear

Right... especialy during the winter time...

[Wnghs2007]

gfs often has strong lows that dont actually appear

Right... especialy during the winter time...

LOL. Yes I posted about it in the Winter weather forum

[Stormsfury]

Convective feedback problem ... especially looking at the 18z GFS run ... a huge spurious QPF BOMB appears over the Upstate of South Carolina and travels rapidly SE across most of South Carolina, and a vort maxima develops a SFC low and ... well, it's a crazy looking scenario ...

EDIT: The strong SFC low holds some weight as the 12z ECMWF swings the low BACK towards the NW to just offshore of the NE Coast ... and then swings in a cyclonic loop around ... but this occurs FURTHER NORTH on the ECMWF run than the 18z GFS run ...

NOGAPS does NOT show this, but not surprised due to the progressive nature of the NAVY model ...

SF