danielwAdministrator
(Moderator)
Tue Oct 16 2007 04:19 AM
Over Night Surprise??

While there isn't much mention about the broad trough in the Western and SW GOM.
I did find a few honorable mentions in the various discussions tonight.

TPC has even generated a model run on the poorly ( at this time ) organized system.
Latest Model Run on the GOM Low

QUANTITATIVE PRECIPITATION FORECAST DISCUSSION
NWS HYDROMETEOROLOGICAL PREDICTION CENTER CAMP SPRINGS MD
607 PM EDT MON OCT 15 2007

FINAL DAY 1...DAY 2 AND DAY 3 QPF DISCUSSION
VALID OCT 16/0000 UTC THRU OCT 19/0000 UTC
REFERENCE AWIPS GRAPHICS UNDER...PRECIP ACCUM - 24HR

DAY 1...( 8PM EDT Monday to 8PM EDT Tuesday)
... E CNTRL GULF COAST...

WHILE QPF(total rainfall amounts) DETAILS ARE NOT EXACT...ALL MODELS GENERATE SGFNT (significant)RAINS INVOF(in vicinity of) THE E CNTRL GULF COAST AS RETURNING PWS(preciptable water amounts) IN THE 2.25 INCH RANGE ARE LIFTED BEHIND AN EVOLVING WARM FRONT AS A STRONG UPPER LVL(level) JET STREAK SWINGS BY CONTRIBUTE TO STRONG DYNAMIC FORCING.
TREND IN BOTH THE NAM AND GFS WHICH HAS STRONG SUPPORT FM(from) THE CANADIAN GEM (model) WAS TO BE FASTER WITH INITIATING ACTVTY(activity) ALONG THE GULF COAST.
FOR NOW LEANED A LITTLE MORE TOWARDS THE GEM FOR THE FCST(forecast) WHICH ALLOWED HEAVIER PCPN(precipitation) TO ADVANCE A LITTLE FARTHER NWD(northward) THAN THE GFS OR NAM WHICH MAY OR MAY NOT BE RELATED TO SOME
FEEDBACK ISSUES. WHETHER THE VERY HEAVY GFS AMTS(amounts) ARE CORRECT OR NOT IS SPECULATIVE..BUT THE MSTR AVBLTY(moisture availability) AND DURATION OF THE ACTVTY(activity)
SUGGESTS THAT AMTS(amounts) COULD APCH(approach) THE 6.00 TO 7.00 INCH GFS TOTALS AT
LEAST ON THE VERY LOCALIZED SCALE.

DAYS 2 AND 3... (Tuesday night thru Wednesday night)

...GULF COAST AND SOUTHEAST...
WITH HEIGHT FALLS OVER THE PLAINS WEDNESDAY AHEAD OF THE SHORTWAVE OVER THE INTERMOUNTAIN WEST.... THE REMAINS OF AN OLD BAROCLINIC ZONE OVER THE SOUTHERN GULF SHOULD BEGIN LIFTING NORTHWARD THE
NEXT FEW DAYS. THIS PATTERN ALONG WITH THE ENTRAINMENT OF MOISTURE ASSOCIATED WITH A WEAK LOW-LEVEL CIRCULATION WEST OF THE
YUCATAN THIS AFTERNOON SHOULD SET THE STAGE FOR MODERATE TO LOCALLY HEAVY RAINS OVER THE EAST CENTRAL GULF COAST INTO PARTS OF THE DROUGHT-STRICKEN SOUTHEAST.

THE NAM AND CMC MODELS WERE CERTAINLY OVERLY DEVELOPED WITH THE BROAD SURFACE LOW OVER THE CENTRAL AND NORTHWEST GULF COAST... WITH THE GFS AND ECMWF GENERALLY FAVORING A WEAK OR ALMOST NON-EXISTENT SURFACE LOW REACHING THE CENTRAL GULF COAST TOWARD THE START OF THE PERIOD.

REGARDLESS OF WHETHER THIS SYSTEM EXISTS OR NOT...OVERRUNNING MOISTURE AND A FAIRLY SLOW-MOVING BOUNDARY SHOULD LEAD TO SOME
HEFTY RAINFALL TOTALS FROM THE MOUTH OF THE MISSISSIPPI AND FLORIDA PANHANDLE INLAND THROUGH ALABAMA AND THE SOUTHERN
APPALACHIANS.

edit: While the system isn't a purely tropical system at this time-1210AM EDT. The combination of the purely tropical airmass, northward moving warm front, and other upper atmosphere disturbances appear to be setting the stage for a Heavy Rainfall event.

Per the HPC maps. The Eastern Gulf Coast is the Coastline east of Appalachicola,FL
http://www.hpc.ncep.noaa.gov/images/us_bndrys2_print.gif

EXCESSIVE RAINFALL DISCUSSION
NWS HYDROMETEOROLOGICAL PREDICTION CENTER CAMP SPRINGS MD
1002 PM EDT MON OCT 15 2007

...VALID 03Z TUE OCT 16 2007 - 00Z WED OCT 17 2007...
...REFERENCE AWIPS GRAPHIC UNDER...DAY 1 EXCESSIVE RAINFALL...

CNTRL GULF COAST...

SATL IMAGERY IS SHOWING CONVECTION TRYING TO ORGANIZE IN AN AXIS
OF HIGH PWS SURGING NWD TOWARD THE CNTRL GULF COAST. MODEL
GUIDANCE CONTS TO SUGGEST THAT THERE WL BE POTENTIAL FOR HEAVY
PCPN AMTS ALONG THE GULF COAST...ALTHOUGH THE GFS APPEARS TO HAVE
SOME GRID SCALE ISSUES. GIVEN THE LATEST SATL IMAGERY AND FAIRLY
GOOD MODEL AGRMNT...BELIEVE THERE WL BE A THREAT OF HEAVY RAINS
SPREADING NWD INTO THE CNTRL GULF COAST OVERNIGHT. ISOLATED SHRT
TERM PCPN AMTS OF 1-2" AND ISOLATED TOTALS APPCHG 5" POSSIBLE
ALONG THE CNTRL GULF COAST THIS PERIOD.

http://www.hpc.ncep.noaa.gov/discussions/qpferd.html

http://www.hpc.ncep.noaa.gov/qpf/qpf2.shtml



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