[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 112353
TWDAT

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
805 PM EDT THU OCT 11 2012

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

BASED ON 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
2315 UTC.

...SPECIAL FEATURES...

TROPICAL DEPRESSION SIXTEEN IS UPGRADED TO TROPICAL STORM PATTY
AT 11/2100 UTC. AT THIS TIME...IT IS CENTERED NEAR 25.8N 72.5W
OR ABOUT ABOUT 255 MI...415 KM NE OF THE CENTRAL BAHAMAS.
PRESENT MOVEMENT IS STATIONARY. ESTIMATED MINIMUM CENTRAL
PRESSURE IS 1007 MB. MAXIMUM SUSTAINED WIND SPEED IS 35 KT WITH
GUSTS TO 45 KT. SEE LATEST NHC FORECAST/ADVISORY UNDER AWIPS/WMO
HEADERS MIATCMAT1/WTNT21 KNHC. PATTY IS EXPECTED TO BE SHORT
LIVED TROPICAL CYCLONE DUE TO A COUPLE OF FACTORS. ONE IS
INCREASING SOUTHWESTERLY SHEAR DURING THE NEXT DAY OR SO. SECOND
IS THE PRESENCE OF A COLD FRONT IN THE WESTERN PORTION OF THE
CIRCULATION PLUS SOME DRIER AND MORE STABLE AIR THAT WILL LIKELY
ENTRAIN INTO THE CENTER. THESE ENVIRONMENTAL CONDITIONS SHOULD
CAUSE THE CYCLONE TO WEAKEN BY TOMORROW AS IT MOVES SLOWLY TO
THE SW AROUND A BUILDING HIGH PRESSURE INTO THE WESTERN ATLANTIC
OCEAN. NUMEROUS MODERATE TO STRONG CONVECTION IS FROM 24N TO 28N
BETWEEN 70W AND 72.5W. SCATTERED MODERATE TO STRONG CONVECTION
IS ELSEWHERE FROM 27N TO 31N BETWEEN 65W AND 72W.

A BROAD AREA OF LOW PRESSURE ASSOCIATED WITH A TROPICAL WAVE IS
LOCATED NEAR 12N59W OR ABOUT 75 MILES EAST-SOUTHEAST OF
BARBADOS. SHOWER AND THUNDERSTORM ACTIVITY CONTINUES TO SHOW
SOME SIGNS OF ORGANIZATION...AND ENVIRONMENTAL CONDITIONS APPEAR
CONDUCIVE FOR GRADUAL DEVELOPMENT OVER THE NEXT COUPLE OF DAYS.
THIS SYSTEM HAS A HIGH CHANCE OF BECOMING A TROPICAL CYCLONE
DURING THE NEXT 48 HOURS AS IT MOVES NORTHWESTWARD AT 10 TO 15
MPH. REGARDLESS OF DEVELOPMENT...STRONG GUSTY WINDS AND HEAVY
RAINFALL ARE POSSIBLE ACROSS PORTIONS OF THE LESSER ANTILLES
DURING THE NEXT COUPLE OF DAYS. A DIFFLUENT PATTERN ALOFT IS
OBSERVED OVER THIS SYSTEM...AND IS HELPING TO SUPPORT THE
CONVECTION ASSOCIATED WITH IT. THUNDERSTORM ACTIVITY HAS ALSO
INCREASED NEAR THE CIRCULATION CENTER. A CLUSTER OF NUMEROUS
MODERATE TO ISOLATED STRONG CONVECTION IS NOTED WITHIN 110 NM NE
QUADRANT OF LOW CENTER. SCATTERED MODERATE ISOLATED STRONG
CONVECTION IS ELSEWHERE FROM 9N TO 16N BETWEEN 50W AND 57W. BUOY
41101 LOCATED NEAR 14.5N56W IS REPORTING SUSTAINED WINDS OF 25
KT AND SEAS TO 11 FT. THE LOW PRES IS FORECAST TO REACH A
POSITION NEAR 15N62W IN ABOUT 24 HOURS.

...THE ITCZ/THE MONSOON TROUGH...

THE MONSOON TROUGH EXTENDS FROM NEAR THE SENEGAL/GUINEA BISSAU
BORDER TO 5N25W...THEN THE ITCZ CONTINUES TO 5N40W TO 9N54W.
ISOLATED MODERATE CONVECTION IS NOTED FROM 4N TO 10N BETWEEN 22N
AND 30N. SIMILAR CONVECTION IS NEAR 10.5N31.5W AND NEAR 8.5N37W.

...DISCUSSION...

GULF OF MEXICO...
A RIDGE/TROUGH PATTERN DOMINATES THE GULF REGION ALOFT. THE
RIDGE EXTENDS FROM AN ANTICYCLONIC CIRCULATION LOCATED OVER
CENTRAL MEXICO NEAR 20N100W TO THE N INTO TEXAS COVERING THE
WESTERN PART OF THE GULF WATERS. THE UPPER-LEVEL TROUGH
STRETCHES FROM THE CAROLINAS ACROSS FLORIDA AND THE SE PORTION
OF THE GULF WITH THE BASE OF THE TROUGH OVER WESTERN CUBA.
MODERATE TO STRONG SUBSIDENCE AND IMPLIED DRY AIR MASS IS NOTED
ACROSS MOST OF THE AREA. SOME CONVECTIVE ACTIVITY HAS FLARED UP
OVER EASTERN TEXAS. AT THE SURFACE...A RIDGE...ANCHORED ON A
HIGH PRES OVER THE SE CONUS...DOMINATES THE GULF. PRES GRADIENT
BETWEEN THE RIDGE AND TROPICAL STORM PATTY WILL BRING AN
INCREASE IN WINDS ACROSS THE EASTERN GULF...INCLUDING ALSO THE
STRAITS OF FLORIDA FRI THROUGH SUN. IN FACT...LATEST
SCATTEROMETER DATA PROVIDED OBSERVATIONS OF 15-20 NE WINDS
ACROSS THIS AREA.

THE CARIBBEAN SEA...
LIGHT TO MODERATE WINDS ARE OBSERVED ACROSS THE CARIBBEAN SEA
DUE TO THE PRESENCE OF TROPICAL STORM PATTY N OF THE AREA.
HOWEVER...EXPECT AN INCREASE IN WINDS OVER NW CARIBBEAN TONIGHT
THROUGH SAT AS STRONG HIGH PRES BUILDS OVER EASTERN U.S. THE GFS
COMPUTER MODELS SUGGESTS WINDS OF MAINLY 20 KT ACROSS WESTERN
CUBA AND THE NW CARIBBEAN. SCATTERED MODERATE TO STRONG
CONVECTION IS OVER PARTS OF COSTA RICA AND PANAMA IN ASSOCIATION
WITH THE MONSOON TROUGH. IN THE UPPER LEVELS...THE ANTICYCLONIC
CIRCULATION CENTERED OVER CENTRAL MEXICO EXTENDS A RIDGE ACROSS
NORTH-CENTRAL AMERICA AND THE WESTERN CARIBBEAN INTO EASTERN
CUBA. AN UPPER LEVEL LOW IS SPINNING OVER THE NE CARIBBEAN AN IS
HELPING TO INDUCE SOME CONVECTIVE ACTIVITY ACROSS PUERTO RICO
AND REGIONAL COASTAL WATERS. BETWEEN THESE TWO UPPER-LEVEL
FEATURES...A NE WIND FLOW ALOFT PREVAILS. THE SAN JUAN DOPPLER
RADAR IS SHOWING SCATTERED SHOWERS AND ISOLATED TSTMS ACROSS THE
REGIONAL WATERS...MORE CONCENTRATED NEAR THE US/UK VIRGIN
ISLANDS AND ACROSS THE CARIBBEAN WATERS. JUST E OF THE LESSER
ANTILLES...THERE IS A LOW PRES SYSTEM WITH THE POTENTIAL OF
BECOMING A TROPICAL CYCLONE. SEE SPECIAL FEATURES FOR MORE
DETAILS. PRES GRADIENT BETWEEN HIGH PRES NEAR 34N41W AND THE
AFOREMENTIONED LOW PRES IS ALREADY PRODUCING FRESH TO STRONG ELY
WINDS ACROSS THE TROPICAL N ATLC FROM 13N AND 18N BETWEEN 55W
AND 60W AS NOTED PER THE MOST RECENT SCATTEROMETER DATA.

THE ATLANTIC OCEAN...
TROPICAL STORM PATTY HAS DEVELOPED JUST E OF THE BAHAMAS. SEE
SPECIAL FEATURES FOR MORE DETAILS. HIGH PRES CENTERED OVER THE
SE UNITED STATES DOMINATES THE STATE OF FLORIDA AND NOW IS
PRODUCING NE WINDS ACROSS SOUTH FLORIDA. THESE WINDS WILL BRING
SOME PATCHES OF SHALLOW MOISTURE WITH EMBEDDED SHOWERS ACROSS
EASTERN FLORIDA. A LARGE 1026 MB HIGH IS OVER THE ATLANTIC NEAR
34N41W COVERING MOST OF THE EAST AND CENTRAL ATLANTIC. IN THE
UPPER LEVELS...THE TROUGH THAT WAS COVERING EASTERN NORTH
AMERICA THE PAST COUPLE OF DAYS NOW IS EXITING THE EAST COAST OF
THE UNITED STATES. AS PREVIOUSLY MENTIONED...THIS TROUGH EXTENDS
FROM THE CAROLINAS ACROSS FLORIDA AND THE SE PORTION OF THE GULF
WITH THE BASE OF THE TROUGH OVER WESTERN CUBA.

FOR ADDITIONAL INFORMATION PLEASE VISIT
HTTP://WWW.HURRICANES.GOV/MARINE

$$
GR




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