[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 172347
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
805 PM 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 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
2315 UTC.

...SPECIAL FEATURES...

TROPICAL STORM OPHELIA CENTERED NEAR 43.1N 65.1W...OR 125 NM SW
OF HALIFAX NOVA SCOTIA...AT 18/0000 UTC MOVING NE 26 KT.
ESTIMATED MINIMUM CENTRAL PRESSURE IS 997 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 CENTER OF OPHELIA HAS BECOME COMPLETELY
EXPOSED AND NOW CONSISTS OF AN AREA OF LOW CLOUDS/SHOWERS S OF
NOVA SCOTIA. A CLUSTER OF DEEP CONVECTION HAS BEEN ADVECTED TO
THE E OF THE CENTER AND IS MOVING AWAY FROM THE SE COAST OF NOVA
SCOTIA. SCATTERED MODERATE CONVECTION FROM 42N-46N BETWEEN
58W-62W. SCATTERED SHOWERS ELSEWHERE N OF 39N BETWEEN 61W-70W.
RADAR IMAGERY FROM ENVIRONMENT CANADA AND THE CANADIAN HURRICANE
CENTER SHOWS A BAND OF CONVECTION S OF NOVA SCOTIA HEADING
QUICKLY N TOWARDS HALIFAX AND SURROUNDING VICINITIES...AND A
BROAD AREA OF LIGHTER RAIN SHOWERS FROM NEW BRUNSWICK TO SE
NEWFOUNDLAND WHERE OPHELIA IS INTERACTING WITH A FRONTAL
BOUNDARY.

TROPICAL DEPRESSION SEVENTEEN CENTERED NEAR 13.8N 55.2W...OR 250
NM E OF BARBADOS...AT 17/2100 UTC MOVING NW 8 KT. ESTIMATED
MINIMUM CENTRAL PRESSURE IS 1006 MB. MAXIMUM SUSTAINED WIND
SPEED IS 30 KT WITH GUSTS TO 40 KT. SEE LATEST NHC FORECAST/
ADVISORY UNDER AWIPS/WMO HEADERS MIATCMAT2/WTNT22 KNHC FOR MORE
DETAILS. DEEP CONVECTION HAS MUSHROOMED OVER AND TO THE S OF THE
LOW-LEVEL CENTER OF THE DEPRESSION...WITH MORE DISORGANIZED
SHOWER ACTIVITY UP TO 500 NM TO THE NE. UPPER LEVEL OUTFLOW
LOOKS GOOD...AND IMPROVING...IN ALL FOUR QUADRANTS SO IT APPEARS
THE DEPRESSION SHOULD SOON STRENGTHEN TO A TROPICAL STORM.
NUMEROUS MODERATE/STRONG CONVECTION FROM 10N-15N BETWEEN
53W-57W. WIDELY SCATTERED MODERATE ELSEWHERE FROM 12N-18N
BETWEEN 50W-54W.

A 1010 MB LOW IS CENTERED ABOUT 145 NM E OF GRAND TURK NEAR
22N68.5W MOVING NW 5-10 KT. THE LOW-LEVEL CIRCULATION OF THIS
SYSTEM HAS BEEN IMPROVING AND STRENGTHENING THROUGH THE DAY
ALTHOUGH THE ASSOCIATED AREA OF TSTMS HAS BEEN A LITTLE RAGGED
AND DISORGANIZED. THE LOW SITS ABOUT 400 NM E OF AN UPPER LOW
WHICH IS CENTERED BETWEEN THE BAHAMAS AND CUBA AND UPPER
DIFFLUENCE IS SUPPORTING NEW TSTM DEVELOPMENT. SCATTERED
MODERATE CONVECTION FROM 21N-25N BETWEEN 67W-70W. TROPICAL
CYCLONE DEVELOPMENT IS POSSIBLE WITHIN THE NEXT 36 HRS FROM JUST
N OF HISPANIOLA TOWARDS THE CENTRAL BAHAMAS...ESPECIALLY IF
CONVECTION CAN PERSIST AND BECOME MORE ORGANIZED AROUND THE
CENTER. MODEL GUIDANCE BRINGS THE LOW THROUGH THE BAHAMAS OVER
THE NEXT 48-72 HRS AND IT IS ADVISED THAT ALL INTERESTS IN THE
BAHAMAS AND SOUTH FLORIDA REMAIN ABREAST OF FUTURE DEVELOPMENTS
ON THIS SYSTEM IN THE COMING DAYS. REGARDLESS OFF TROPICAL
DEVELOPMENT...HEAVY RAINFALL WILL SPREAD FROM THE SOUTHERN
BAHAMAS WWD TOWARDS THE NORTHERN BAHAMAS...S FLORIDA...AND CUBA
THROUGH MID-WEEK.

...TROPICAL WAVES...

EAST ATLANTIC TROPICAL WAVE TILTED FROM 7N29W TO 18N32W...WITH A
1009 MB LOW NEAR 10N30W...MOVING W 10 KT. THE WAVE CONTINUES TO
DISPLAY A SHARP LOW-LEVEL SIGNATURE WITH CONVERGENCE MAXIMIZED
ALONG THE NRN END OF THE AXIS. THE LOW APPEARS TO BE EMBEDDED
WITHIN THE ITCZ AND WITHIN A RELATIVE VOID OF DEEP CONVECTION.
SCATTERED MODERATE CONVECTION FROM 14N-18N BETWEEN 28W-32W.
SCATTERED MODERATE FROM 8N-12N BETWEEN 32W-37W.

EAST CARIBBEAN TROPICAL WAVE ALONG 68W BENDING BACK NE ACROSS
PUERTO RICO TO 23N65W...MOVING W 10-15 KT. THE SAN JUAN UPPER
AIR SOUNDING FROM THIS MORNING INDICATES THAT A WEAK BOUNDARY
MOVED PAST OVERNIGHT...AND THIS AGREES WITH SATELLITE IMAGERY
WHICH SHOWS A WEAK APEX SLIDING INTO THE MONA PASSAGE.
CONVECTION HAS BEEN FOCUSED ALONG THE NRN EXTENT OF THE WAVE
WITH WIDELY SCATTERED MODERATE N OF PUERTO RICO FROM 19N-22N
BETWEEN 62W-65W.

...ITCZ...

ITCZ AXIS IS CENTERED ALONG 9N15W 8N20W 14N29W...THEN ALONG
7N32W 5N38W 8N46W...THEN 12N68W 9N83W. SCATTERED MODERATE
CONVECTION FROM 5N-10N BETWEEN 20W-29W. NUMEROUS MODERATE/STRONG
OVER EXTREME NW VENEZUELA NEAR LAKE MARACAIBO. WIDELY SCATTERED
MODERATE S OF 11N BETWEEN 77W-85W EXTENDING ACROSS PANAMA AND
COSTA RICA.

...DISCUSSION...

GULF OF MEXICO...
LARGE HIGH PRES IN THE UPPER LEVELS OF THE ATMOSPHERE IS
CENTERED OVER SE TEXAS AND BROAD NE/E FLOW IS ADVECTING A
SIGNIFICANT AREA OF DRY AIR ACROSS FLORIDA AND THE GULF WATERS N
OF 23N. A LITTLE BIT OF MOISTURE HAS SNUCK IN S OF THE RIDGE
WHICH HAS ALLOWED SCATTERED TSTMS TO DEVELOP OVER THE YUCATAN
PENINSULA...AND ONLY ISOLATED SHOWERS OVER THE BAY OF CAMPECHE.
A FEW OTHER TSTMS HAVE ALSO DEVELOPED OVER S FLORIDA DRIFTING SW
TOWARDS W CUBA. CONDITIONS WILL REMAIN RELATIVELY DRY ACROSS THE
AREA THROUGH MON BEFORE AN AREA OF LOW PRES...POSSIBLY A
TROPICAL CYCLONE...APPROACHES THE STRAITS OF FLORIDA EARLY NEXT
WEEK.

CARIBBEAN...
A LARGE UPPER LOW IS CENTERED OVER E/CENTRAL CUBA NEAR 22N77W
WITH A TROUGH AXIS EXTENDING SW TO NE HONDURAS. INSTABILITY
ASSOCIATED WITH THE LOW HAS YIELDED A FAVORABLE ENVIRONMENT FOR
SCATTERED TSTMS TO FORM ACROSS THE ENTIRE LENGTH OF CUBA. SOME
DRY AIR IS BEING ADVECTED INTO THE NW CARIBBEAN BEHIND THE UPPER
TROUGH BUT STILL ISOLATED SHOWERS/TSTMS EXTEND FROM JAMAICA
TOWARDS ERN HONDURAS/NE NICARAGUA. A BROAD UPPER HIGH IS
CENTERED N OF PANAMA NEAR 11N80W WITH UPPER DIFFLUENCE
TRIGGERING SCATTERED SHOWERS/TSTMS FROM 10N-15N BETWEEN 78W-83W.
FARTHER E...A BROAD UPPER HIGH LOCATED OVER T.D. 17 TO THE E OF
THE LESSER ANTILLES EXTENDS WWD INTO THE E CARIBBEAN WITH S/SW
FLOW BRINGING SOME HIGH LEVEL CLOUDS ACROSS MOST OF THE LEEWARD
AND WINDWARD ISLANDS. HOWEVER...A PATCH OF STRONG SUBSIDENCE
EXTENDS FROM THE NRN LEEWARDS SW TO THE COAST OF COLOMBIA AND IS
KEEPING SKIES MOSTLY FAIR FOR THE NIGHT.

WEST ATLANTIC...
A SHARP UPPER LEVEL TROUGH...THE ONE RESPONSIBLE FOR PICKING UP
T.S. OPHELIA...IS SLIDING OFF THE U.S. EAST COAST AND JUST
REACHES SWD OFF THE N FLORIDA COAST. AN UPPER LOW IS LOCATED SE
OF THE TROUGH ALONG THE N COAST OF CUBA NEAR 22N77W WITH
SCATTERED MODERATE CONVECTION FROM ANDROS ISLAND SWD FROM
22N-25N BETWEEN 76W-80W. AN UPPER RIDGE HAS DEVELOPED FROM
20N62W TO 27N70W NE OF THE SFC LOW NEAR HISPANIOLA...AND IS
PROVIDING OUTFLOW TO THE N AND E WHICH IS HELPING TO FOSTER
CONVECTIVE DEVELOPMENT. A 50 KT OUTFLOW JET EXTENDS EWD INTO THE
CENTRAL ATLC FROM 20N-24N ON THE S SIDE OF AN ELONGATED UPPER
LOW CENTERED NEAR 27N55W. A SURFACE TROUGH IS LOCATED N OF T.D.
17 AND IS MOVING W 15-20 KT WITH SCATTERED MODERATE CONVECTION
FROM 19N-23N BETWEEN 54W-59W.

CENTRAL/EAST ATLANTIC...
A LARGE UPPER LEVEL ANTICYCLONE IS EMBEDDED IN THE TROPICS NEAR
12N46W TO THE E OF T.D. 17...AND IS HELPING TO PROVIDE THE
NECESSARY OUTFLOW TO SUSTAIN THE DEPRESSION. THE E ATLC IS
DOMINATED BY A 40-50 KT WESTERLY JET ALONG 20N WITH WEAK
TROUGHING CENTERED ALONG 30W TO THE W OF THE CAPE VERDE ISLANDS.
A WEAK TROUGH ALSO EXTENDS E/W OVER THE SUBTROPICS FROM 30N20W
27N40W...JUST NW OF THE CANARY ISLANDS. FARTHER S...AN UPPER
HIGH IS LOCATED OFF THE COAST OF GUINEA-BISSAU NEAR 12N19W WITH
DIFFLUENCE SUPPORTING AN AREA OF CONVECTION ALONG THE ITCZ.

$$
BERG


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