[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 140003
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
805 PM EDT MON OCT 13 2008

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...METEOROLOGICAL ANALYSIS...WEATHER
OBSERVATIONS...AND RADAR.

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

...SPECIAL FEATURES...
TROPICAL DEPRESSION NANA IS CENTERED NEAR 17.5N 40.6W AT 13/2100
UTC OR ABOUT 960 NM WEST OF THE CAPE VERDE ISLANDS MOVING WNW AT
8 KT. ESTIMATED MINIMUM CENTRAL PRESSURE IS 1007 MB. MAXIMUM
SUSTAINED WIND SPEED IS 30 KT WITH GUSTS TO 40 KT. PLEASE SEE
LATEST NHC PUBLIC ADVISORY UNDER AWIPS/WMO HEADERS MIATCPAT4/
WTNT34 KNHC AND THE FULL FORECAST/ADVISORY UNDER AWIPS/WMO
HEADERS MIATCMAT4/WTNT24 KNHC FOR MORE DETAILS. WESTERLY SHEAR
HAS DECREASED CONVECTION NEAR NANA AS THE SYSTEM CONTINUES TO
WEAKEN THIS EVENING. SCATTERED MODERATE CONVECTION IS WITHIN 90
NM OF THE CENTER IN THE NE QUADRANT. ELSEWHERE SCATTERED
MODERATE CONVECTION IS SE OF THE CENTER FROM 13N-17N BETWEEN
36W-39W. NANA IS FORECAST TO WEAKEN INTO A REMNANT LOW TONIGHT
OR TUESDAY.

TROPICAL DEPRESSION FIFTEEN IS CENTERED NEAR 14.5N 69.4W AT
14/0000 UTC OR ABOUT 310 NM SW OF SAN JUAN PUERTO RICO REMAINING
NEARLY STATIONARY. LITTLE MOTION IS EXPECTED DURING THE NEXT 24
HOURS. HOWEVER...A NE MOTION IS FORECAST TO BEGIN ON LATE
TUESDAY OR EARLY WEDNESDAY BRINGING THE CYCLONE VERY CLOSE TO
PUERTO RICO OR THE VIRGIN ISLANDS. ESTIMATED MINIMUM CENTRAL
PRESSURE IS 1001 MB. MAXIMUM SUSTAINED WIND SPEED IS 30 KT WITH
GUSTS TO 40 KT. PLEASE SEE LATEST NHC PUBLIC ADVISORY UNDER
AWIPS/WMO HEADERS MIATCPAT5/WTNT35 KNHC AND THE FULL FORECAST/
ADVISORY UNDER AWIPS/WMO HEADERS MIATCMAT5/WTNT25 KNHC FOR MORE
DETAILS. NUMEROUS MODERATE/STRONG CONVECTION IS LOCATED WITHIN
160 NM OF THE CENTER IN THE ERN SEMICIRCLE. SCATTERED MODERATE/
ISOLATED STRONG CONVECTION IS LOCATED FROM 12N-19N BETWEEN
60W-70W.

A 1006 MB LOW PRESSURE IS IN THE WRN CARIBBEAN SEA NEAR
14N82W...A SHORT DISTANCE EAST OF THE COAST OF NICARAGUA. THIS
LOW IS ACCOMPANIED BY A LARGE AREA OF DISTURBED WEATHER WITH
SCATTERED MODERATE/ISOLATED STRONG CONVECTION FROM 11N-19N
BETWEEN 78W-86W. CONDITIONS APPEAR FAVORABLE FOR ADDITIONAL
DEVELOPMENT AND THE SYSTEM COULD BECOME A TROPICAL DEPRESSION
DURING THE NEXT COUPLE OF DAYS AS IT MOVES SLOWLY NORTHWESTWARD.

...TROPICAL WAVES...
A WEAK TROPICAL WAVE IS ALONG 50W S OF 20N MOVING W NEAR 15 KT.
THE WAVE IS EMBEDDED IN AN AREA OF MODERATE TO STRONG SUBSIDENCE
KEEPING ANY ASSOCIATED SHOWERS CONFINED TO THE ITCZ ALONG 11N
BETWEEN 49W-52W.

A TROPICAL WAVE IS ALONG 60W SOUTH OF 20N MOVING WEST NEAR 10
KT. THE WAVE IS QUICKLY BECOMING ABSORBED INTO T.D. FIFTEEN AS
IT TRACKS WESTWARD. POSSIBLE SCATTERED SHOWERS ARE ACROSS
BARBADOS AND THE CENTRAL LESSER ANTILLES THIS EVENING...BUT MOST
OF THIS ACTIVITY IS ATTRIBUTED TO T.D. FIFTEEN AND AN UPPER
DIFFLUENT PATTERN ACROSS THE ERN CARIBBEAN SEA.

...THE ITCZ...
ITCZ AXIS IS CENTERED ALONG 11N17W 9N30W 12N40W 12N43W 11N49W
10N52W 10N58W. A 1008 MB LOW IS EMBEDDED WITHIN THE ITCZ NEAR
13N42W. SCATTERED MODERATE/ISOLATED STRONG CONVECTION IS FROM
12N-14N BETWEEN 40W-42W IN ASSOCIATION WITH THE SURFACE LOW.
ELSEWHERE...SCATTERED MODERATE/ISOLATED STRONG CONVECTION IS
FROM 9N-12N BETWEEN 19W-30W. CLUSTERS OF SCATTERED MODERATE
CONVECTION ARE FROM 5N-11N BETWEEN 30W-37W.

...DISCUSSION...

GULF OF MEXICO...
AN UPPER RIDGE EXTENDS OVER ERN TEXAS INTO NE MEXICO PRODUCING
DRY NORTHERLY UPPER FLOW AND STABLE ATMOSPHERIC CONDITIONS NW OF
A LINE FROM SE LOUISIANA TO NEAR VERACRUZ MEXICO. AN UPPER-LEVEL
LOW IS CENTERED IN THE WRN BAY OF CAMPECHE NEAR 20N95W AND
CONTINUES MOVING WESTWARD. LOW-LEVEL INSTABILITY AND MOIST
SOUTHERLY MID-HIGH LEVEL FLOW TO THE EAST OF THIS FEATURE IS
HELPING TO INDUCE SCATTERED SHOWERS AND TSTMS OVER THE CENTRAL
AND ERN GULF...INCLUDING THE SRN FLORIDA PENINSULA. THIS
ACTIVITY REMAINS S OF 28N AND E OF 92W. A HIGH PRESSURE CENTER
OVER THE MID-ATLANTIC STATES DOMINATES THE SE CONUS AND NRN
FLORIDA PENINSULA. THE PRESSURE GRADIENT BETWEEN THIS HIGH AND
THE BROAD AREA OF LOW PRESSURE ACROSS THE WRN CARIBBEAN SEA IS
GENERATING MODERATE TO STRONG ELY WINDS OVER THE ERN GULF.

CARIBBEAN SEA...
TWO AREAS OF CONCERN ACROSS THE CARIBBEAN SEA...ONE IS T.D.
FIFTEEN IN THE ERN CARIBBEAN...AND THE SECOND ONE IS A BROAD
AREA OF LOW PRESSURE IN THE WRN CARIBBEAN...SEE SPECIAL FEATURES
FOR MORE DETAILS. UPPER LEVEL RIDGING COVERS MUCH OF THE
CARIBBEAN WHICH IS AIDING IN GENERATING THE CONVECTIVE ACTIVITY
ASSOCIATED WITH T.D. FIFTEEN AND THE AREA OF LOW PRESSURE OVER
THE WRN CARIBBEAN. CLUSTERS OF SCATTERED MODERATE/ISOLATED
STRONG CONVECTION ARE ACROSS THE WRN CARIBBEAN W OF 77W DUE TO A
LARGE AREA OF UPPER DIFFLUENCE CREATED FROM THE UPPER LOW OVER
THE SW GULF OF MEXICO AND THE RIDGING ACROSS THE WRN CARIBBEAN.
MUCH OF THE CONVECTION ASSOCIATED WITH T.D. FIFTEEN REMAINS E OF
71W WITH DEEP LAYERED MOISTURE IN PLACE ACROSS THE CENTRAL AND
ERN CARIBBEAN.

ATLANTIC OCEAN...
T.D. NANA CONTINUES TO MOVE OVER THE OPEN WATERS OF THE TROPICAL
ATLC...SEE SPECIAL FEATURES ABOVE. SCATTERED SHOWERS AND TSTMS
ARE ACROSS THE FAR W ATLC...NW BAHAMAS AND SRN FLORIDA PENINSULA
THIS EVENING FROM 24N-28N W OF 76W. THIS ACTIVITY IS MOVING WWD
UNDER EASTERLY SURFACE FLOW AROUND A HIGH PRESSURE SYSTEM
LOCATED OVER THE MID-ATLANTIC STATES. A WEAK SURFACE TROUGH...
ASSOCIATED WITH BROAD UPPER TROUGHING ACROSS THE W ATLC...
EXTENDS INTO THE DISCUSSION AREA NEAR 32N47W TO 27N51W. ANOTHER
SURFACE TROUGH EXTENDS FROM 27N57W TO 24N61W. POSSIBLE SCATTERED
SHOWERS ARE WITHIN 150 NM OF BOTH SURFACE TROUGHS ACROSS THE
CENTRAL ATLC. A RIDGE ANCHORED ON AN UPPER-LEVEL HIGH NEAR
11N30W DOMINATES THE TROPICS AND IS ENHANCING CONVECTION ALONG
THE ITCZ. A SURFACE TROUGH IS ALONG THE W AFRICAN COAST
EXTENDING FROM 19N16W TO THE ITCZ AXIS NEAR 11N16W. NO
SIGNIFICANT PRECIPITATION IS OBSERVED ON SATELLITE IMAGERY...BUT
HOURLY SURFACE OBSERVATIONS SHOW A WIND SHIFT ALONG THE COAST.
FURTHER NORTH...A SURFACE RIDGE OF HIGH PRESSURE ANCHORED ON A
1022 MB HIGH CENTERED NEAR 33N28W INFLUENCES THE NE ATLC N OF
20N AND E OF 41W.

$$
HUFFMAN


This weather bulletin was brought to you by:
www.nashvilleweather.net