[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 081744
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
205 PM EDT SAT OCT 08 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 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
1715 UTC.

...SPECIAL FEATURE...

SUBTROPICAL DEPRESSION TWENTY-TWO HAS FORMED AND IS CENTERED
NEAR 28.6N 59.9W...OR 335 NM SE OF BERMUDA...AT 08/1800 UTC
MOVING WNW 13 KT. ESTIMATED MINIMUM CENTRAL PRESSURE IS 1009 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 AND THE PUBLIC ADVISORY UNDER HEADERS MIATCPAT2/
WTNT32 KNHC FOR MORE DETAILS. AFTER HAVING A BAND OF INTENSE
CONVECTION EARLIER THIS MORNING...THE DEPRESSION HAS BECOME A
LITTLE LESS IMPRESSIVE AND THE CENTER IS BEING EXPOSED ON THE S
SIDE OF A CLUSTER OF TSTMS. THE DEPRESSION IS EMBEDDED WITHIN A
BROAD UPPER LEVEL CYCLONIC GYRE AND HAS GENERATED A MORE
SUBTROPICAL THAN TROPICAL SIGNATURE WITH AN EXPANDED AND
ASYMMETRIC WIND FIELD. SCATTERED SHOWERS/TSTMS ARE CURRENTLY
LOCATED WITHIN A BAND TO THE N AND E OF THE CENTER FROM 26N-31N
BETWEEN 54W-62W. SHOWERS/TSTMS ARE EXPECTED TO BEGIN SPREADING
OVER BERMUDA TONIGHT AND ON SUN AS TROPICAL MOISTURE IS PULLED
NWD.

...TROPICAL WAVES...

UPPER AIR DATA FROM DAKAR INDICATES THAT A TROPICAL WAVE MOVED
OFF THE AFRICAN COAST ABOUT 36 HRS AGO AROUND 06 UTC OCT 7...AND
PASSED SAL IN THE CAPE VERDES WITHIN THE PAST 6-12 HRS. THE WAVE
MAY NOT ACTUALLY HAVE A SURFACE REFLECTION SINCE THE DATA AT
BOTH SITES ONLY INDICATE A WIND SHIFT ABOVE 850-900 MB.
NONETHELESS...THE WAVE WILL BE ADDED TO THE 1800 UTC SURFACE
ANALYSIS IN THE VICINITY OF 26W.

EAST/CENTRAL ATLANTIC TROPICAL WAVE ALONG 33W/34W S OF 14N
MOVING W 10-15 KT. THE WAVE IS LOW-AMPLITUDE AND HAS A RATHER
FLAT SIGNATURE YET THERE IS STILL A FAIRLY WELL-DEFINED
CIRCULATION ALONG 8N. ONLY ISOLATED SHOWERS FROM 6N-11N BETWEEN
33W-36W.

CENTRAL ATLANTIC TROPICAL WAVE ALONG 49W S OF 20N MOVING W 5-10
KT. A CLOSED CIRCULATION HAS BEEN COMING AND GOING ALONG THE
WAVE AXIS AND LATEST VIS PICTURES SHOW A POSSIBLE LOW NEAR
14N51W. DEEP CONVECTION REMAINS FOCUSED ALONG THE N PART OF THE
WAVE...AS IT HAS BEEN FOR THE PAST FEW DAYS...WITH SCATTERED
MODERATE FROM 13N-20N BETWEEN 46W-51W.

CENTRAL CARIBBEAN TROPICAL WAVE ALONG 74W S OF 20N MOVING W 10
KT. THE WAVE HAS AN EXTREMELY POOR SIGNATURE AND IS MAINLY
TRACKED BY TSTMS OCCURRING NEAR THE WINDWARD PASSAGE. SCATTERED
MODERATE CONVECTION FROM 16.5N-22N BETWEEN 72W-77W SPREADING
OVER PARTS OF HISPANIOLA...E CUBA...SRN BAHAMAS...AND JAMAICA.

...ITCZ...

ITCZ AXIS IS CENTERED ALONG 12N10W 8N18W 11N31W...THEN ALONG
7N35W 15N47W...THEN ALONG 12N50W 15N60W. SCATTERED MODERATE
CONVECTION FROM 10N-13N BETWEEN 10W-16W. WIDELY SCATTERED
SHOWERS/TSTMS 2N-8N BETWEEN 10W-30W.

...DISCUSSION...

GULF OF MEXICO...
A "COLD FRONT" CONTINUES TO MOVE SLOWLY ACROSS THE GULF WATERS
AND IS ANCHORED BY A 1004 MB LOW WHICH IS LOCATED JUST W OF
TAMPA BAY FLORIDA NEAR 28N83W. THE GRADIENT BEHIND THE FRONT IS
RATHER WEAK SO THE AIR MASS COMING OFF THE CONTINENTAL U.S. IS
QUICKLY BEING MODIFIED BY THE WARM GULF WATERS AND THERE IS
LITTLE TEMPERATURE OR DEWPOINT CHANGE. THE BOUNDARY EXTENDS FROM
THE LOW SW TO THE N YUCATAN COAST THEN ALONG THE CAMPECHE COAST.
A STATIONARY SEGMENT CONTINUES TO LIE INLAND ACROSS MEXICO FROM
18N96W TO 27N107W WITH PATCHY LOW CLOUDS AND VALLEY FOG TO THE
N...ESPECIALLY NEAR THE COAST. THE FRONT ALSO EXTENDS NE OF THE
LOW PAST JACKSONVILLE INTO THE CAROLINAS. SHOWER ACTIVITY NEAR
THE FRONT IS MINIMAL...PARTLY DUE TO MODERATE/STRONG SUBSIDENCE
OVER THE AREA IN ASSOCIATION WITH A LARGE UPPER LOW NEAR 28N87W.
ISOLATED SHOWERS ARE NOTED ALONG THE MEXICAN COAST BETWEEN
VERACRUZ AND TAMPICO...AND THIS ACTIVITY IS EXPECTED TO SHIFT N
TOWARDS THE TEXAS COAST OVER THE NEXT 48 HRS AS RETURN SLY FLOW
BECOMES ESTABLISHED.

CARIBBEAN...
THE ATMOSPHERE REMAINS QUITE MOIST ACROSS THE CARIBBEAN AS THE
UPPER LOW OVER THE GULF OF MEXICO ADVECTS PACIFIC MOISTURE INTO
THE NW CARIBBEAN...AND THEN THE UPPER RIDGE FROM HONDURAS TO THE
BAHAMAS RECIRCULATES THIS MOISTURE SWD OVER THE E/CENTRAL
CARIBBEAN. CONVECTION IS PRIMARILY BEING FORCED BY SEVERAL
LOW-LEVEL BOUNDARIES. THE FIRST IS A SURFACE TROUGH EXTENDING
FROM W CUBA TO THE GULF OF HONDURAS WHICH IS TRIGGERING
SCATTERED MODERATE CONVECTION FROM 16N-23N BETWEEN 78W-88W
(BELIZE AND HONDURAS TO THE CAYMAN ISLANDS AND CNTRL CUBA).
SECOND...A SURFACE TROUGH APPEARS TO BE DEVELOPING NEAR THE SRN
BAHAMAS AND IS INTERACTING WITH A TROPICAL WAVE ALONG 74W TO
PRODUCE SCATTERED MODERATE CONVECTION FROM THE WINDWARD PASSAGE
TO JAMAICA. THIRD...AN AXIS OF LOW-LEVEL SPEED CONVERGENCE
STRETCHING FROM S OF PUERTO RICO NEAR 17N69W EWD ACROSS THE NRN
LEEWARD ISLANDS HAS PRODUCED AN AREA OF SCATTERED MODERATE
CONVECTION FROM 14N-18N E OF 63W AND AFFECTING THE ISLANDS
BETWEEN ST. LUCIA AND ANTIGUA.

WEST/CENTRAL ATLANTIC...
A PRE-FRONTAL TROUGH LIES ALONG 78W...AHEAD OF THE COLD FRONT
MOVING ACROSS THE SOUTHEAST U.S...AND APPEARS TO HAVE MERGED
WITH A NEW TROUGH WHICH IS DEVELOPING LENGTHWISE ACROSS THE
SOUTHERN BAHAMAS. AN UPPER LEVEL RIDGE IS LOCATED OVER THE
TROUGH ALONG 76W AND IS PROVIDING A FAVORABLY DIFFLUENT
ENVIRONMENT FOR SCATTERED MODERATE CONVECTION WITHIN 120 NM OF A
LINE FROM 20N72W 26N76W 32N75W. A DEEP UPPER LEVEL TROUGH IS
LOCATED ALONG 61W WITH AN EMBEDDED UPPER LOW NEAR 23N62W...AND
THIS FEATURE IS WHAT LED TO THE DEVELOPMENT OF SUBTROPICAL
DEPRESSION TWENTY-TWO. ASIDE FROM CONVECTION NEAR THE
DEPRESSION...SCATTERED MODERATE CONVECTION HAS ALSO FORMED
FARTHER S FROM 13N-22N BETWEEN 54W-62W...AND FARTHER E FROM
22N-29N BETWEEN 44W-51W.

EAST ATLANTIC...
A LARGE UPPER LEVEL HIGH IS CENTERED WITHIN THE TROPICS NEAR
12N36W AND IS PROVIDING THE CONTRAST OF WET WEATHER W OF 40W AND
DRY WEATHER E OF 40W. THE MOST SIGNIFICANT FEATURE IS A
DEEP-LAYERED TROUGH WHOSE MAIN AXIS IS ALONG 32N21W 17N29W. AN
UPPER LOW IS EMBEDDED WITHIN THE TROUGH NEAR 33N20W AND ODDLY
ENOUGH A TIGHT CORE OF CONVECTION HAS DEVELOPED WITHIN 45 NM OF
THE CENTER...GIVING THE SYSTEM AN ALMOST TROPICAL APPEARANCE. A
SURFACE TROUGH EXTENDS S AND SE OF THE LOW FROM THE WESTERN
CANARY ISLANDS SW TO 23N30W AND IS ALONG THE LEADING EDGE OF A
STRATOCUMULUS FIELD. ISOLATED SHOWERS MAY MOVE ACROSS THE CANARY
AND MADEIRA ISLANDS...BUT THIS SYSTEM IS MOSTLY COLD-CORE AND IS
NOT EXPECTED TO BECOME TROPICAL OVER THE COLDER WATERS OF THE NE
ATLC. FARTHER E...THE DEEP TROUGH IS ADVECTING TROPICAL MOISTURE
ALL THE WAY UP TO THE STRAITS OF GIBRALTAR AND SCATTERED
MODERATE CONVECTION HAS FORMED OVER MOROCCO AND WESTERN SAHARA
FROM 23N-32N BETWEEN 8W-15W.

$$
BERG


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