[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 291021
TWDAT

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
805 AM EDT TUE SEP 29 2015

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 0600 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
1015 UTC.

...SPECIAL FEATURES...

TROPICAL STORM JOAQUIN IS LOCATED AT 26.6N 70.6W AT 0900 UTC OR
ABOUT 334 NM NE OF THE CENTRAL BAHAMAS. THE ESTIMATED MINIMUM
CENTRAL PRESSURE IS 1002 MB. MAXIMUM SUSTAINED WIND SPEED IS 35
KT WITH GUSTS TO 45 KT. NUMEROUS MODERATE/ISOLATED STRONG
CONVECTION IS FROM 23N-26N BETWEEN 68W-71W...SCATTERED MODERATE
CONVECTION AND ISOLATED TSTMS ARE ELSEWHERE FROM 20N-27N BETWEEN
66W-73W. SEE LATEST NHC FORECAST/ADVISORY UNDER AWIPS/WMO
HEADERS MIATCMAT1/WTNT21 KNHC FOR MORE DETAILS.

...TROPICAL WAVES...

A TROPICAL WAVE IS OVER THE E ATLC E OF THE CAPE VERDE ISLANDS
WITH TILTED AXIS EXTENDING FROM 16N18W SW TO A 1010 MB LOW
PRESSURE CENTER EMBEDDED IN THE MONSOON TROUGH NEAR 10N23W. SSMI
TOTAL PRECIPITABLE WATER IMAGERY SHOW THE WAVE IS EMBEDDED
MAINLY IN A MODERATE MOIST ENVIRONMENT THAT ALONG WITH MIDDLE
LEVEL DIFFLUENCE AHEAD OF THE SURFACE LOW SUPPORT SCATTERED TO
ISOLATED MODERATE CONVECTION AND TSTMS WITHIN 100 NM EITHER SIDE
OF THE WAVE AXIS AND FROM 06N TO 12N BETWEEN 22W AND 26W.

...ITCZ/MONSOON TROUGH...

THE MONSOON TROUGH EXTENDS FROM THE AFRICAN COAST NEAR 11N15W TO
A 1010 MB LOW NEAR 10N23W TO 09N35W TO 09N43W. THE INTERTROPICAL
CONVERGENCE ZONE AXIS EXTENDS FROM 09N43W TO THE COAST OF GUYANA
NEAR 06N57W. ASIDE FROM THE CONVECTION ASSOCIATED WITH THE
TROPICAL WAVE...SCATTERED MODERATE CONVECTION IS FROM 04N-07N
BETWEEN 15W-24W AND FROM 05N TO 12N BETWEEN 26W AND 42W.

...DISCUSSION...

GULF OF MEXICO...

SURFACE LOW PRESSURE CONTINUES TO DOMINATE ACROSS THE
GULF...EXCEPT IN THE SW BASIN WHERE A WEAK 1011 MB HIGH PRESSURE
CENTER IS BEING ANALYZED. ALOFT...A MIDDLE TO UPPER LEVEL LOW
AND ASSOCIATED TROUGH EXTEND FROM ARKANSAS SW TO CENTRAL MEXICO
AND INFLUENCE A 1006 MB LOW PRESSURE CENTER LOCATED IN THE NW
GULF NEAR 28N93W. ANOTHER 1006 MB LOW PRESSURE CENTER IS IN THE
NE BASIN FROM WHICH A SURFACE TROUGH EXTENDS SE ALONG 28N83W TO
26N82W. TROUGHING AT THE UPPER LEVELS OVER THE WESTERN HALF OF
THE BASIN AND A RIDGE OVER THE NW CARIBBEAN CONTINUE TO GENERATE
A DIFFLUENT ENVIRONMENT ALOFT THAT ALONG WITH MOISTURE INFLOW
FROM THE CARIBBEAN AND EPAC WATERS SUSTAIN SCATTERED MODERATE
CONVECTION FROM 26N TO 29N E OF 84W AND ISOLATED SHOWERS
ELSEWHERE SE OF A LINE FROM 29N89W TO 23N97W. EXCEPT FOR THE E
GULF E OF 84W...WINDS ARE 15 KT OR LESS AND VARIABLE. THE UPPER
LEVEL LOW AND ASSOCIATED NEARLY COLLOCATED SURFACE LOW IS
EXPECTED TO BE SLOW TO MOVE THE NEXT FEW DAYS WHILE THE EASTERN
GULF LOW ACCELERATES NORTHWARD TO THE FLORIDA BIG BEND REGION
WITHIN THE NEXT 24 HOURS. ASIDE FROM POTENTIAL TROPICAL CYCLONE
DEVELOPMENT...THE MAIN IMPACT WILL CONTINUE TO BE CONVECTIVE
PRECIPITATION...HEAVY AT TIMES...AND POTENTIAL FLOODING ACROSS
FLORIDA.

CARIBBEAN SEA...

A SURFACE TROUGH CURRENTLY EXTENDING FROM THE NORTHERN YUCATAN
PENINSULA TO GUATEMALA ALONG WITH ABUNDANT MOISTURE OVER THE FAR
NW CARIBBEAN SUPPORT SCATTERED SHOWERS AND TSTMS S OF 21N W OF
85W. MODERATE SHALLOW MOISTURE OVER THE SW BASIN AND THE MONSOON
TROUGH EXTENDING FROM COSTA RICA TO NORTHERN COLOMBIA SUPPORT
ISOLATED SHOWERS AND TSTMS S OF 10N. SIMILAR CONVECTION IS
OBSERVED OVER HISPANIOLA BEING INFLUENCED BY TROPICAL STORM
JOAQUIN LOCATED IN THE SW N ATLC. SEE SPECIAL FEATURES FOR MORE
INFORMATION. WATER VAPOR IMAGERY INDICATE RELATIVELY STRONG DRY
AIR ALOFT IN ASSOCIATION WITH A BROAD AND ELONGATED UPPER LEVEL
LOW CENTERED NEAR 17N60W. OTHERWISE...MAINLY FRESH TO OCCASIONAL
STRONG TRADES PERSIST WITH THE STRONGEST WINDS NOTED ACROSS
SOUTH-CENTRAL PORTIONS.

...HISPANIOLA...

MOISTURE ASSOCIATED WITH TROPICAL STORM JOAQUIN IN THE SW N ATLC
IS BEING ADVECTED BY CYCLONIC FLOW ACROSS THE ISLAND...THUS
SUPPORTING ISOLATED SHOWERS AND TSTMS. PRECIPITATION ACTIVITY IS
EXPECTED TO CEASE LATE TUESDAY AS THE STORM MOVES W-NW OVER ATLC
WATERS.

ATLANTIC OCEAN...

THE MAIN FEATURE OVER THE ATLC IS TROPICAL STORM JOAQUIN
DISCUSSED IN SPECIAL FEATURES. THE REMAINDER OF THE SW NORTH
ATLC IS UNDER THE INFLUENCE OF MOSTLY NORTH-NORTHEASTERLY FLOW
ALOFT ON THE EASTERN PERIPHERY OF AN UPPER LEVEL RIDGE ANCHORED
OVER THE OFFSHORE WATERS OF THE FLORIDA PENINSULA NEAR 28N77W.
TO THE ESE OF JOAQUIN...A LARGE AREA OF DISTURBED WEATHER IS IN
THE CENTRAL ATLC ASSOCIATED WITH A FRONTAL TROUGH AND THE
REMNANTS OF IDA. THE CENTER OF THIS DISTURBANCE IS A 1010 MB LOW
NEAR 23N54W FROM WHICH A TROUGH EXTENDS FROM 24N57W TO THE LOW
TO 20N52W. SCATTERED MODERATE CONVECTION AND TSTMS ARE FROM 20N
TO 24N BETWEEN 49W AND 56W. A CLUSTER OF MODERATE/ISOLATED
STRONG CONVECTION IS FROM 24N TO 27N BETWEEN 56W AND 59W. A
BROAD UPPER TROUGH OVER THE CENTRAL N ATLC SUPPORTS A COLD FRONT
ALONG 30N30W TO 25N40W TO 26N50W WHERE IT TRANSITIONS INTO A
STATIONARY FRONT TO 27N60W TO 30N65W. SCATTERED MODERATE
CONVECTION IS WITHIN 120 NM EITHER SIDE OF THE FRONTAL BOUNDARY.

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

$$
NR
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