[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 121754
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
205 PM EDT WED OCT 12 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.

...TROPICAL WAVES...

E ATLC WAVE ADDED BETWEEN W AFRICA AND THE CAPE VERDES ALONG 19W
S OF 15N MOVING W 10 KT.  LONG-TERM SATELLITE PICTURES SUGGEST A
WAVE HAS EMERGED FROM AFRICA.  IN ADDITION 24 HOUR PRESSURE
RISES OVER W AFRICA ARE UP TO 4 MB.  A SQUALL LINE ALONG 10N25W
13N25W IS AHEAD OF THE WAVE WHICH IS PRODUCING SCATTERED
MODERATE CONVECTION FROM 4N-8N BETWEEN 14W-24W.

E-CENTRAL ATLC WAVE IS TILTED NNW TO SSE FROM 6N29W TO 16N32W
MOVING W 10 KT.  STRONGER-THAN-AVERAGE LOW-LEVEL WLY FLOW IN THE
ITCZ SEEMS TO BE TILTING THE WAVE IN THE E ATLC.  VISIBLE IMAGES
SHOW LOW/MID LEVEL ROTATION WITHIN ABOUT 60 NM OF THE WAVE AXIS
WITH UPPER DIFFLUENCE AIDING WIDELY SCATTERED MODERATE
CONVECTION FROM 6N-10N BETWEEN 27.5W-32.5W.

CENTRAL ATLC WAVE IS ALONG 42W/43W S OF 17N MOVING W 5-10 KT. A
DECENT INVERTED-V LOW LEVEL SIGNATURE IS NOTED IN ADDITION TO
WITH A LOW-LEVEL CIRCULATION ALONG THE WAVE AXIS.  ISOLATED
MODERATE CONVECTION IS FROM 12N-20N BETWEEN 39W-46W WITH A
NEARBY UPPER TROUGH STRONGLY SHEARING THE WAVE FROM THE SW.

W-CENTRAL ATLC WAVE IS ALONG 53W S OF 16N MOVING W 10 KT.  THE
WAVE HAS ALWAYS BEEN FAIRLY LOW-AMPLITUDE AND NOW AN UPPER
TROUGH ALMOST CO-LOCATED WITH THE WAVE IS MAKING ANY DETECTION
OF THE WAVE DIFFICULT.  SCATTERED MODERATE CONVECTION FROM
9N-11N BETWEEN 48W-55W.

WEAK E CARIBBEAN WAVE LOCATED OVER THE LESSER ANTILLES IS ALONG
65W S OF 20N MOVING W 5-10 KT.  ANY ENERGY FROM THE WAVE APPEARS
TO BE GETTING PULLED NORTHWARD INTO THE LARGE LOW OVER THE W
ATLC AND THE WAVE IS VERY DIFFICULT TO TRACK.  IT IS POSSIBLE
THAT SCATTERED TSTMS FROM 12.5N-15N BETWEEN 66.5W-68.5W ARE
ASSOCIATED WITH THE WAVE.

...ITCZ...

ITCZ AXIS IS CENTERED ALONG 10N14W 7N24W 10N41W 11N57W.
SCATTERED MODERATE CONVECTION IS FROM 9N-11N BETWEEN 48W-55W.
ISOLATED MODERATE FROM 5N-10N BETWEEN 29W-37W.

...DISCUSSION...

GULF OF MEXICO...
NEARLY STATIONARY MID/UPPER HIGH SITS NEAR 26N84W IN THE E GULF
WITH DRY AIR ALOFT CONTROLLING THE REGION.  ISOLATED SHOWERS/FEW
TSTMS ARE ALONG THE COAST OF NE MEXICO... OTHERWISE SKIES ARE
MOSTLY CLEAR EXCEPT FOR CENTRAL AND NE FLORIDA.  LOW CLOUDS AND
ISOLATED SHOWERS ARE STUCK BEHIND A WEAK TROUGH IN THE W ATLC...
AN ARTIFACT OF LONG-LASTING NLY SURFACE WINDS IN THE AREA ALONG
WITH NO DISTURBANCES TO REMOVE THE MOISTURE.  SOMEWHAT CLOUDY
WET WEATHER SHOULD REMAIN FOR A FEW DAYS IN NE MEXICO AND
EXTREME S TEXAS WITH MOIST NE FLOW.  SIMILAR CONDITIONS ARE
LIKELY IN NE FLORIDA BEFORE BEING SHOVED SOUTHWARD BY A WEAK
COLD FRONT THAT SHOULD BRING MUCH DRIER AIR THRU S FLORIDA BY
SUN.  GENERALLY NE WINDS OF 10-15 KT LOOK TO BE THE RULE WITH
BROAD HIGH PRESSURE OVER THE CONUS DOMINATING.

CARIBBEAN SEA...
SAME WEATHER DIFFERENT DAY IN THE CARIBBEAN AND W ATLC.  AN
ANOMALOUS PATTERN REMAINS WITH STRONG W TO WSW FLOW IN THE
MID/UPPER LEVELS CONTROLLING THE AREA S OF A TROUGH AXIS FROM
THE WINDWARD PASSAGE TO NE NICARAGUA.  SECOND WEAK TROUGH AXIS
EXTENDS FROM A 1005 MB JUST W OF HAITI NW TO JUST S OF WRN CUBA.
ISOLATED TSTMS ARE ALONG THE SECOND TROUGH.  VERY HIGH MOISTURE
LEVELS S OF THE FIRST TROUGH AND UPPER DIFFLUENCE IS CONTINUING
TO PRODUCE A LARGE AREA OF UNSETTLED WEATHER OVER THE CARIBBEAN
SE OF THE TROUGH.  SCATTERED SHOWERS/TSTM COVER THE REGION N OF
S AMERICA BETWEEN 68W-81W.   STATIONARY UPPER HIGH IS NEAR
16N76W PROVIDING PLENTY OF UPPER DIFFLUENCE FOR NEARBY
SHOWERS/TSTMS.   HEAVY RAIN CONTINUES NEAR PUERTO RICO IN
ASSOCIATION WITH UPPER DIFFLUENCE AND PLENTIFUL MOISTURE.  A
LINE OF CONVECTION HAS MOVED OFFSHORE FROM 20N64W TO 16N65W
ACROSS THE US VIRGIN ISLANDS.  HEAVY RAIN... FLASH FLOODING AND
THE POTENTIAL FOR LIFE-THREATENING MUDSLIDES EXISTS IN THE N
CARIBBEAN WITH THIS WEATHER SYSTEM ESPECIALLY IN HIGHER
TERRAIN.   THE HIGHER MOISTURE AXIS TROPICAL MOISTURE IS
EXPECTED TO REMAIN OVER MOST OF THE CARIBBEAN W OF THE LESSER
ANTILLES AND S OF CUBA THROUGH LATE WEEK WITH AN ENHANCED CHANCE
OF FLOODING ESPECIALLY IN HISPANIOLA.  THINGS COULD GET A LITTLE
DRIER IN PUERTO RICO IN A COUPLE DAYS BUT THE MOISTURE AXIS WILL
STILL BE VERY CLOSE TO THE ISLAND... PROVIDING AN ENHANCED
CHANCE OF RAIN.

ATLANTIC OCEAN...
ERN FLANK OF MID/UPPER HIGH CONTROLS THINGS W OF 75W WITH DRY
AIR ALOFT.  A MID/UPPER TROUGH WITH TWO LOWS LIES FROM THE FIRST
LOW NEAR 33N69W SSW TO A SECOND LOW CENTER NEAR THE TURKS/CAICOS
ISLANDS THEN SW INTO SE CUBA.  A SURFACE TROUGH REMAINS FROM
30N66W TO A 1005 MB LOW NEAR 26N66.5W CONTINUING SW INTO THE
WINDWARD PASSAGE.  VISIBLE SATELLITE PICTURES SUGGEST ANOTHER
LOW HAS FORMED NEAR 29N65W.  A LARGE AREA OF DISTURBED WEATHER
IS ON THE E SIDE OF THE TROUGH WITH SCATTERED SHOWERS & TSTMS
WITHIN 360 NM E OF A LINE FROM 20N70W TO 31N64W.  COMPUTER
MODELS STILL SUGGEST A NEAR-STORM FORCE LOW COULD FORM AT THE
NORTHERN END OF THE TROUGH BUT IT IS UNKNOWN WHETHER THE LOW
WILL BE MORE OF THE NON-TROPICAL OR SUBTROPICAL VARIETY.
FARTHER E... UPPER RIDGING LIES OVER THE CENTRAL ATLC FROM THE
NE CARIBBEAN TO 27N51W STRETCHING NE TO 31N42W.  MODERATE/STRONG
SUBSIDENCE IS S OF THE RIDGE AXIS N OF 20N W OF 40W.  A
MID/UPPER TROUGH IS ORIENTED FROM NE TO SW E OF THE RIDGE AXIS
FROM 31N31W INTO A CLOSED LOW NEAR 16N48W.  DIVERGENCE/LIFT ON
THE S SIDE OF THE TROUGH IS CAUSING SOME ITCZ AND WAVE-RELATED
CONVECTION TO FLARE THIS AFTERNOON.  THIS UPPER LOW IS FORECAST
TO MOVE WESTWARD WITH UPPER RIDGING BUILDING WESTWARD IN THE
DEEP TROPICS.  IN THE NE ATLC... ZONAL WLY FLOW DOMINATES ON THE
N SIDE OF A FLAT MID/UPPER HIGH IN THE DEEP TROPICS NEAR
10N24W.  THE HIGH IS FARTHER N THAN AVERAGE AND SHOULD SHIFT TO
THE WNW AS UPPER TROUGHING DROPS IN THE NE ATLC IN A FEW DAYS.
WEAK COLD FRONT HAS PULLED UP STATIONARY ALONG 31N16W TO 31N30W
WITH ONLY ISOLATED SHOWERS WITHIN 60 NM OF THE BOUNDARY.
OTHERWISE TYPICAL HIGH PRESSURE COVERS THE SURFACE IN THE E
ATLC.  THE TROPICAL WAVES ARE WEAK AND CLOSE TOGETHER WITH A
WAVELENGTH OF 10-12 DEGREES.

$$
BLAKE


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