[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 221709
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
105 PM EST FRI DEC 22 2006

TROPICAL WEATHER DISCUSSION FOR NORTH AMERICA...
CENTRAL AMERICA...THE GULF OF MEXICO...THE CARIBBEAN SEA...
NORTHEASTERN SECTIONS OF SOUTH AMERICA...AND THE ATLANTIC
OCEAN TO THE AFRICAN COAST FROM THE EQUATOR TO 32N.
THE FOLLOWING INFORMATION IS BASED ON SATELLITE IMAGERY...
METEOROLOGICAL ANALYSIS...WEATHER OBSERVATIONS...AND RADAR.

BASED ON 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
1715 UTC.

...THE ITCZ...
ITCZ AXIS IS CENTERED ALONG 5N8W 2N29W 5N46W 5N53W. SCATTERED
MODERATE CONVECTION IS WITHIN 120 NM EITHER SIDE W OF 38W.
ISOLATED MODERATE IS WITHIN 90 NM EITHER SIDE BETWEEN 10W-16W.

...DISCUSSION...
GULF OF MEXICO...
ABUNDANT MOISTURE REMAINS IN PORTIONS OF GULF...NOW SHIFTING A
LITTLE TO E COVERING MUCH OF THE NRN HALF OF THE REGION. THERE
ARE A FEW ELEMENTS PRODUCING THIS UNSETTLED WEATHER. FIRST IN
THE UPPER LEVELS...A LARGE LOW PRES SYSTEM CONTINUES TO MOVE TO
THE NE NOW CENTERED IN THE UPPER PLAINS. STRONG SWLY FLOW TO THE
E OF THE LARGE CUT OFF ALONG WITH A SUBTROPICAL JET MERGING WITH
THE UPPER FLOW IN PLACE IS ENHANCING INSTABILITY. AT THE
SFC...THE FRONTAL BOUNDARY IS NOW ON THE MOVE...AFTER BEING
NEARLY STATIONARY FOR THE PAST 18-24 HOURS...AND IS ANALYZED
FROM ERN LA S-SW ALONG 26N92W 23N94W 20N96W. THE WEAK SFC LOW
THAT HAS BEEN ALONG THE FRONT IS DROPPED FROM THE MAP AS LITTLE
EVIDENCE ON SAT IMAGERY OR IN SFC OBS WAS APPARENT. DOPPLER
RADAR SHOWS BANDS OF SCATTERED SHOWERS AND TSTMS IN THE WARM
SECTOR FROM THE BIG BEND AREA OF FL TO SE LA. DOPPLER DERIVED
ACCUMULATED RAINFALL PRODUCTS FROM THE SE SHOWS ISOLATED
RAINFALL TOTALS TO 4-5 INCHES ACROSS PARTS OF CENTRAL GA. IR
IMAGERY SHOWS MOISTURE STREAMING E TOWARDS THE FL PENINSULA AS
THE COLD FRONT APPROACHES. THE WRN PERIPHERY OF THE SFC RIDGE
STRETCHES ACROSS FLORIDA AND THE E GULF. THE TIGHTENED GRAD
BETWEEN THIS HIGH PRES...CENTERED NEAR BERMUDA...AND LOWER PRES
IN THE CENTRAL GULF IS GENERATING 20 TO 25 KT S TO SE WINDS IN
THE E GULF AND THE FL BEACHES. THESE WINDS WILL SUBSIDE WITHIN
THE NEXT 24 HOURS. LOOKING AHEAD...THE COLD FRONT WILL BECOME
STATIONARY TONIGHT/TOMORROW BEFORE A STRONGER SECOND COLD
FRONT...ASSOCIATED WITH A SHORT WAVE TROUGH CURRENTLY OVER THE
WRN U.S...ENTERS THE WRN GULF SAT NIGHT. SEVERAL OF THE COMPUTER
MODELS FORECAST A SFC LOW TO FORM ALONG THE FRONT LATE SAT/EARLY
SUN AND TRACK IT NE ACROSS THE AREA. WINDS ARE FORECAST TO
INCREASE TO GALE FORCE BEHIND THE FRONT IN THE WRN GULF ON SUN.

CARIBBEAN SEA...
AN UPPER LEVEL TROUGH IS SLOWLY SLIDING EASTWARD ACROSS THE
CARIBBEAN WITH THE AXIS EXTENDING FROM THE WINDWARD PASSAGE TO
PANAMA. A FAIR AMOUNT OF DRY STABLE AIR IN THE MID AND UPPER
LEVEL RESIDES ACROSS THE WRN AND CNTRL PORTION...THANKS TO UPPER
LEVEL CONFLUENT FLOW BETWEEN THIS TROUGH AND A STRONG MID TO
UPPER LEVEL HIGH CENTERED OVER EL SALVADOR. UPPER LEVEL
DIFFLUENCE...SOME LOW LEVEL CONVERGENCE ALONG WITH LOCAL UPSLOPE
FLOW IS PRODUCING SCATTERED SHOWERS ACROSS THE DOMINICAN
REPUBLIC AND ISOLATED ACTIVITY ACROSS ERN CUBA. THE ERN
CARIBBEAN HAS MAINLY FAIR CONDITIONS LYING ON THE NW SIDE OF AN
EXTENSIVE UPPER LEVEL RIDGE. 50-70 KT WLY UPPER LEVEL FLOW IS
ADVECTING SOME HIGH CLOUDINESS ACROSS THE AREA S OF 14N. AT THE
SFC...SHIP...BUOY AND QSCAT DATA SHOWS AN AREA OF 20-25 KT TRADE
WINDS BETWEEN 68W AND 78W. THESE WINDS WILL LIKELY REMAIN AT
THIS STRENGTH AND EXPAND EASTWARD OVER THE NEXT FEW DAYS AS HIGH
PRES SETTLES IN THE SUBTROPICAL CENTRAL ATLC. GFS SHOWS THE TAIL
END OF A COLD FRONT MOVING INTO THE NW CARIB ON MON. THIS
FEATURE WILL BRING AN INCREASE IN MOISTURE AHEAD OF IT AND
STRONG NLY WINDS AND INCREASE IN SEAS BEHIND IT.

ATLANTIC OCEAN...
A LONG WAVE RATHER FLAT DEEP-LAYERED RIDGE COVERS THE WRN
ATLC W OF 60W. AN UPPER LEVEL TROUGH IN THE CARIB IS ERODING THE
SRN PERIPHERY OF IT. BROKEN PATCHES OF MID TO HIGH CLOUDINESS IS
ROTATING AROUND THE RIDGE...CONTAINED MOSTLY N OF 30N. A PAIR OF
1030 MB SFC HIGHS ARE CENTERED NEAR 31N61W AND NEAR 33N66W
ENHANCING FAIR WEATHER ACROSS THE REGION. QSCAT DATA SHOWS
NE-ELY WINDS NEAR 20 KT WITH A FEW 25 KT WIND VECTORS S OF 27N
BETWEEN 60W-75W. THESE WINDS ARE DRIVING BROKEN LOW CLOUDS WITH
POSSIBLE EMBEDDED ISOLATED SHOWERS ACROSS THE W ATLC WATERS.
MODELS SHOWS THE SFC RIDGE GETTING PUSHED TO THE SE AND THEN
BECOMING STATIONARY IN THE CENTRAL ATLC EARLY NEXT WEEK. A SHARP
TROUGH LIES TO THE E OF THE RIDGE WITH THE UPPER LEVEL AXIS
EXTENDING ALONG 32N41W 19N47W. THE ASSOCIATED FRONTAL BOUNDARY
IS SLOW MOVING...ANALYZED AS STATIONARY ON THE 12Z MAP ALONG
32N38W 23N48W. MOIST SWLY UPPER LEVEL FLOW ALONG WITH SFC LIFT
NEAR THE BOUNDARY IS GENERATING SCATTERED SHOWERS WITHIN 120 NM
E OF THE FRONT. A MORE AMPLIFIED STACKED RIDGE LIES TO THE E OF
THE TROUGH COVERING THE ATLC WATERS E OF 35W. PLENTY OF DRY AIR
ALOFT IS ASSOCIATED WITH THE RIDGE KEEPING CONDITIONS STABLE
UNDERNEATH IT. THERE IS A WEAK LINGERING SFC TROUGH ALONG 31W
FROM 23N-33N MOVING W STEERED BY THE LOW-LEVEL FLOW. THIS
FEATURE IS A BENIGN SWIRL OF LOW CLOUDS...ONLY CAUSING A WIND
SHIFT AND MAYBE AN ISOLATED SHOWER WITHIN 120 NM. IN THE DEEP
TROPICS...SWIFT UPPER LEVEL ZONAL FLOW ON THE N SIDE OF AN
EXTENSIVE FLAT RIDGE WITH BROKEN HIGH CLOUDINESS IS COMMON.
UPPER DIFFLUENCE NEAR THE W PERIPHERY OF THE RIDGE IS ENHANCING
CONVECTION IN THE ITCZ W OF 40W.

$$
CANGIALOSI






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