[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 171035
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
805 AM EDT SAT SEP 17 2005

TROPICAL WEATHER DISCUSSION FOR NORTH AMERICA...CENTRAL
AMERICA...GULF OF MEXICO...CARIBBEAN SEA...NORTHEASTERN 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
1045 UTC.

...SPECIAL FEATURES...

TROPICAL STORM OPHELIA IS CENTERED NEAR 39.5N 70.7W...OR ABOUT
130 MILES... 205 KM... SOUTH-SOUTHWEST OF NANTUCKET MASSACHUSETTS
AND ABOUT 505 MILES... 815 KM...SOUTHWEST OF HALIFAX NOVA
SCOTIA...AT 17/0900 UTC MOVING NE 18 KT. ESTIMATED MINIMUM
CENTRAL PRESSURE IS 1000 MB. MAXIMUM SUSTAINED WIND SPEED IS 50
KT WITH GUSTS TO 60 KT. SEE LATEST NHC FORECAST/ADVISORY UNDER
AWIPS/WMO HEADERS MIATCMAT1/WTNT21 KNHC AND THE PUBLIC ADVISORY
UNDER HEADERS MIATCPAT1/WTNT31 KNHC FOR MORE DETAILS. THE
MID-LATITUDE WESTERLIES AND STRONG SHEAR HAS DISPLACED
CONVECTION WELL NE OF THE CENTER. SCATTERED MODERATE TO ISOLATED
STRONG CONVECTION IS FROM 39N-43N BETWEEN 65W-70W.

A TROPICAL DISTURBANCE...1008 MB LOW...IS CENTERED ABOUT 320 NM
E OF BARBADOS NEAR 12N54W MOVING WNW 10-15 KT.  SATELLITE
IMAGERY INDICATES THAT THE CIRCULATION AROUND THE SURFACE LOW
HAS INTENSIFIED AND IS ABOUT TO BE UPGRADED TO A TROPICAL
DEPRESSION.  THE SYSTEM IS EMBEDDED IN A BROAD DIFFLUENT UPPER
LEVEL ENVIRONMENT AND WILL REMAIN SO FOR THE NEXT SEVERAL DAYS.
HEAVY SHOWERS/TSTMS ARE EXPECTED TO SPREAD OVER THE LESSER
ANTILLES LATER TODAY AND SUN.  PRESENTLY...SCATTERED MODERATE TO
STRONG CONVECTION IS FROM 10N-15N BETWEEN 51W-56W.  PATCHES OF
SCATTERED MODERATE CONVECTION ARE FROM 15N-20N BETWEEN 47W-53W.

AN AREA OF SHOWERS/TSTMS EXTENDING UP TO 300 NM N OF PUERTO RICO
AND THE VIRGIN ISLANDS IS BEING PRODUCED BY A COMBINATION OF A
SURFACE TROUGH ALONG 24N65W 20N70W...A TROPICAL WAVE ALONG
66W...AND AN UPPER LEVEL LOW CENTERED N OF HISPANIOLA NEAR
23N71W. THE CONVECTION LIES ON THE DIFFLUENT E SIDE OF THE UPPER
LOW. A SURFACE LOW HAS NOT DEVELOPED AS OF YET...BUT THIS COULD
OCCUR SOON IF THE CONVECTION CAN BE MAINTAINED FOR A PROLONGED
PERIOD OF TIME. ASSUMING THE LOW WILL DEVELOP...TROPICAL CYCLONE
DEVELOPMENT WILL BE POSSIBLE IN AN AREA FROM N OF THE VIRGIN
ISLANDS INTO THE EXTREME SRN BAHAMAS WITHIN THE NEXT 36 HRS.
SCATTERED MODERATE TO STRONG CONVECTION IS FROM 20N-23N BETWEEN
60W-67W.

...TROPICAL WAVES...

EAST ATLANTIC TROPICAL WAVE IS ALONG 30W/31W S OF 17N MOVING W
10 KT. THE LATEST SATELLITE IMAGERY SHOWS A LOW AMPLITUDE BUT
WELL-DEFINED AND SHARP SIGNATURE ABOUT 350 NM SW OF THE CAPE
VERDE ISLANDS.  SCATTERED MODERATE/ ISOLATED STRONG CONVECTION
IS MAINLY AHEAD OF THE WAVE NEAR THE ITCZ FROM 3N-10N BETWEEN
27W-37W. WIDELY SCATTERED SHOWERS/TSTMS ELSEWHERE FROM 10N-16N
BETWEEN 27W-32W.

TROPICAL WAVE CROSSING THE LESSER ANTILLES IS ALONG 66W S OF
21N MOVING W 10-15 KT.  CONVECTION IS CONFINED TO N OF 20N.

...ITCZ...

ITCZ AXIS IS CENTERED ALONG 10N15W 11N30W 6N40W 6N45W 12N54W
9N60W.   IN ADDITION TO CONVECTION MENTIONED IN THE TROPICAL
WAVE SECTION...SCATTERED MODERATE TO STRONG CONVECTION IS OFF
THE COAST OF W AFRICA FROM 5N-10N BETWEEN 14W-23W.

...DISCUSSION...

GULF OF MEXICO...
A 1019 MB HIGH IS LOCATED OVER THE NE GULF OF MEXICO NEAR
27N88W PRODUCING FAIR WEATHER AND LIGHT WINDS.  A PATCH OF
SCATTERED MODERATE CONVECTION IS OVER THE BAY OF CAMPECHE FROM
17N-22N BETWEEN 95W-98W MOVING W.  IN THE UPPER LEVELS...AN
UPPER HIGH IS OVER TEXAS NEAR 31N97W PRODUCING NORTHERLY FLOW
OVER THE W GULF W OF 86W.  A SMALL UPPER LOW IS OVER S MEXICO
NEAR 18N97W WITH CYCLONIC FLOW WITHIN 180 NM OF THE CENTER.
EXPECT THE GULF OF MEXICO TO BE RELATIVELY FREE OF CONVECTION
EXCEPT FOR THE THE YUCATAN PENINSULA AND THE BAY OF CAMPECHE
OVER THE NEXT 24 HOURS.

CARIBBEAN...
MODERATE TRADEWINDS ARE OVER THE CARIBBEAN SEA WITH A TROPICAL
WAVE OVER THE E CARIBBEAN.  SCATTERED MODERATE TO ISOLATED
STRONG CONVECTION IS OVER N COLOMBIA FROM 5N-10N BETWEEN
76W-79W.  SCATTERED MODERATE CONVECTION IS ALONG THE COAST OF
NICARAGUA FROM 10N-13N BETWEEN 81W-84W.  SIMILAR CONVECTION IS
ALONG THE COAST OF HONDURAS FROM 14N-16N BETWEEN 82W-85W.
SCATTERED MODERATE TO ISOLATED STRONG CONVECTION IS ALSO OVER
THE GULF OF HONDURAS FROM 15N-17N BETWEEN 85W-90W.  IN THE
UPPER LEVELS... AN UPPER HIGH IS OFF THE COAST OF NICARAGUA NEAR
12N82W ENHANCING CONVECTION N OF PANAMA.  AN UPPER LOW IS N OF
HISPANIOLA NEAR 23N71W.  A TROUGH AXIS EXTENDS W FROM THIS
CENTER TO 20N86W.  THIS FEATURE IS PRODUCING MOISTURE FROM
HISPANIOLA TO HONDURAS.   EXPECT THE HIGHEST POTENTIAL OF
CONVECTION TO BE OVER THE SW CARIBBEAN AND CENTRAL AMERICA S OF
HONDURAS DURING THE NEXT 24 HOURS.

ATLANTIC...
A 1026 MB HIGH IS OVER THE CENTRAL ATLANTIC NEAR 38N51W.  BROAD
EASTERLY SURFACE FLOW IS OVER THE SUBTROPICAL ATLANTIC FROM
20N-30N E OF 60W.  IN THE UPPER LEVELS...A BROAD UPPER LOW
CENTERED NEAR 23N71W IS MOVING W TOWARDS THE SRN BAHAMAS AT
10-15 KT AND IS DRAGGING DRY AIR FROM OVER TH W ATLC WATERS
TOWARDS THE BAHAMAS AND FLORIDA. HOWEVER...THE DIFFLUENT E SIDE
OF THE LOW HAS BEEN FOSTERING CONVECTIVE DEVELOPMENT N OF PUERTO
RICO AND IT IS POSSIBLE THAT A SURFACE LOW...OR TROPICAL CYCLONE
...MAY DEVELOP OVER THE NEXT FEW DAYS N OF HISPANIOLA. FARTHER E
...A WEAK UPPER LOW IS CENTERED NEAR 30N55W.  A 60 KT JET S OF
THIS UPPER LOW IS PRODUCING STRONG WESTERLY SHEAR OVER THE
CENTRAL ATLC BETWEEN 16N-26N...BUT THE TROPICAL DISTURBANCE E OF
THE LESSER ANTILLES IS TOO FAR S TO BE AFFECTED BY THIS
ENVIRONMENT. AN OLD FRONTAL BOUNDARY EXTENDS NE AND INTO THE
TSTMS N OF PUERTO RICO ALONG 31N45W 26N60W WITH ISOLATED
SHOWERS/TSTMS WITHIN 60 NM OF THE BOUNDARY BETWEEN 50W-59W. AN
UPPER HIGH IS CENTERED OVER THE E ATLC NEAR 12N40W WITH A RIDGE
EXTENDING WWD ACROSS THE TROPICAL DISTURBANCE AND EWD TO NEAR
11N30W. BROAD DIFFLUENCE ON THE SE SIDE OF THE RIDGE IS ALSO
FOSTERING CONVECTIVE DEVELOPMENT WITH THE TROPICAL WAVE ALONG
30W/31W DEEP INTO THE TROPICS. THE UPPER FLOW OVER THE
SUBTROPICAL E ATLC IS GENERALLY LIGHT AND VARIABLE.

$$
FORMOSA



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