[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 011055
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
805 AM EDT SAT OCT 1 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
1015 UTC.

...SPECIAL FEATURES...

TROPICAL DEPRESSION NINETEEN IS NEAR 13.3N 34.0W...OR 695 MILES
WSW OF THE CAPE VERDE ISLANDS...AT 01/0900 UTC AND IS
STATIONARY. 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
MIATCMAT4/WTNT24 KNHC FOR MORE DETAILS.  A MICROWAVE PASS
REVEALED THE CENTER WAS ON THE EXTREME NORTHERN EDGE OF THE DEEP
TSTM ACTIVITY.  CONVECTION HAS BEEN MOVING A LITTLE CLOSER TO
THE CENTER WITH SCATTERED MODERATE WITHIN 60 NM OF LINE 15.5N33W
10.5N34W.  THERE IS A BANDING FEATURE TRYING TO FORM IN THE ERN
SEMICIRCLE COMPRISED OF WIDELY SCATTERED MODERATE CONVECTION
FROM 9N-13N BETWEEN 27W-31W.  HOWEVER FIRST VISIBLE IMAGES
SUGGEST A SHEARED SYSTEM.  SLOW INTENSIFICATION SEEMS TO BE THE
BEST BET.

1006 MB LOW IS LOCATED OVER THE NW CARIBBEAN NEAR 19N85W MOVING
WNW ABOUT 5 KT.  THE LOW APPEARS TO BE A LITTLE BETTER ORGANIZED
THAN EARLIER TODAY WITH INCREASING BANDING FEATURES.  IN
ADDITION PRESSURES HAVE BEEN SLOWLY FALLING NEAR THE LOW
CENTER.  THIS SYSTEM HAS THE POTENTIAL TO BECOME A TROPICAL
CYCLONE WITHIN 36 HOURS OR NEAR YUCATAN OR THE SRN GULF.  AN
UPPER LOW IS NW OF THE SURFACE LOW... SOMEWHAT HINDERING ITS
DEVELOPMENT BUT ALL MODELS SUGGEST THIS UPPER FEATURE WILL FADE
WITH TIME AND CREATE MORE RIDGE ALOFT AFTER THE LOW ENTERS THE
GULF OF MEXICO IN A DAY OR TWO.

...TROPICAL WAVES...

E ATLC WAVE ADDED ALONG 20W S OF 20N MOVING W 10 KT.  THIS
POSITION MIGHT BE A LITTLE BEHIND THE TRUE WAVE AXIS IF THE GFS
IS CORRECT... WHICH SUGGESTS IT IS COUPLE DEGREES WEST.
ISOLATED MODERATE CONVECTION IS WITHIN 120 NM BEHIND THE WAVE
AXIS FROM 11N-16N.

CENTRAL CARIBBEAN TROPICAL WAVE ALONG 73W/74W S OF 23N MOVING W
15-20 KT. THE WAVE IS NEXT TO IMPOSSIBLE TO FIND AT NIGHT WITH
CIRRUS MASKING ANY LOW-LEVEL WAVE SIGNATURE SO THE POSITION IS
BASED ON EXTRAPOLATION.  THERE IS NO CLEAR TSTM PATTERN EITHER
AS ISOLATED MODERATE CONVECTION IS SPECKLED ACROSS THE REGION
FROM 14N-18N BETWEEN 72W-78W.

...ITCZ...

ITCZ AXIS IS CENTERED ALONG 11N14W 6N21W 9N29W 8N35W 10N42W
11N49W 15N56W.  WIDELY SCATTERED MODERATE FROM 3N-7N BETWEEN
20W-30W.  SIMILAR CONVECTION WITHIN 60 NM OF ITCZ BETWEEN
41W-46W.  SCATTERED MODERATE FROM 9N-12N BETWEEN 47W-51.5W AND
ISOLATED MODERATE WITHIN 60 NM OF LINE 12N51.5W 18N56W.

...DISCUSSION...

GULF OF MEXICO...
DRY AIR ALOFT IS THE RULE ACROSS ALMOST THE ENTIRE GULF REGION
WITH THE CLOSEST DEEP-LAYERED MOISTURE KEPT AT BAY OVER THE
YUCATAN CHANNEL.  SCATTERED TSTMS ARE LIKELY FOR S FLORIDA LATER
DURING DAYTIME HEATING... OTHERWISE ISOLATED ACTIVITY IS
FORECAST OVER WATER MOSTLY OF THE SHALLOW VARIETY.  A WEAK UPPER
LOW SITS JUST N OF THE YUCATAN CHANNEL NEAR 22N87W DRIFTING
SLOWLY W AND WILL MAKE THE STRAITS OF FLORIDA AND W CUBA QUITE
WET TODAY.  ELSEWHERE... A SMALL 1010 MB LOW IS MOVING SW 10-15
KT OVER THE W GULF WATERS NEAR 24N95W WITH ISOLATED TSTMS WITHIN
90 NM OF THE CENTER.  ISOLATED SHOWERS ARE ALSO IN THE BAY OF
CAMPECHE MOST LIKELY DUE TO AN UPPER TROUGH ALONG THE MEXICAN
COAST.  THE GFS CONTINUES TO SUGGEST THAT A SLUG OF LOW/MID
LEVEL MOISTURE FROM S FLORIDA WILL MOVE WESTWARD RAPIDLY ACROSS
THE GULF.. AFFECTING S TEXAS OVERNIGHT MON.

CARIBBEAN...
AN UPPER LEVEL HIGH CENTERED JUST SW OF THE CAYMAN ISLANDS AND
AN UPPER LOW NE OF THE LEEWARD ISLANDS ARE PRODUCING STRONG NLY
SHEAR OVER MOST OF THE AREA.  WIDELY SCATTERED TSTMS ARE MOSTLY
N OF 16N W OF 75W IN THE BEST UPPER DIFFLUENCE AND NEAR THE
TROPICAL DISTURBANCE IN THE W CARIBBEAN.  A 1006 MB LOW...AS
DESCRIBED IN SPECIAL FEATURES...IS NEAR 19N86W AND HAS A BURST
OF CONVECTION OVER IT THIS MORNING ALONG WITH SEVERAL BANDING
FEATURES.  THE E CARIBBEAN AND LESSER ANTILLES...E OF ABOUT
67W...ARE UNDER THE SUBSIDENT REGIME OF THE UPPER LOW NE OF THE
AREA AND ITS TRAILING TROUGH AXIS THAT EXTENDS TO ISLA
MARGARITA...SO SKIES ARE MAINLY CLEAR AND WINDS ARE GENERALLY
LIGHT.  WETTER-THAN-AVERAGE CONDITIONS ARE LIKELY IN THE W
CARIBBEAN FOR THE NEXT COUPLE DAYS WHILE MOSTLY DRY WEATHER
CONTINUES IN THE E CARIBBEAN.  ONE EXCEPTION COULD BE IN THE
LESSER ANTILLES WHERE A LITTLE UPPER INSTABILITY COULD ENHANCE
SHOWER ACTIVITY.

ATLANTIC WEST OF 50W...
AN UPPER LEVEL TROUGH AXIS IS LOCATED OVER THE W ATLC WATERS
FROM 32N75W TO THE NW BAHAMAS AND IS ASSISTING SHOWERS N OF 29N
W OF 70W.  OTHERWISE AN AREA OF UPPER DIFFLUENCE TO THE S AND A
WEAK TROUGH IS PRODUCING WIDELY SCATTERED SHOWERS/TSTMS FROM
20N-23N BETWEEN 68W-72W.  PLENTIFUL MOISTURE REMAINS THROUGHOUT
THE BAHAMAS AND SHOULD REFIRE SHOWER/TSTMS ACROSS THE AREA
DURING THE DAY.  W ATLC UPPER LOW IS LOCATED NEAR 22N61W AND IS
KICKING OFF ISOLATED TSTMS FROM 17.5N-26N BETWEEN 58W-65W. THE
UPPER LOW/TROUGH HAS CREATED LIGHT WINDS E OF THE LESSER
ANTILLES AND A DIFFUSE ITCZ.

ATLANTIC EAST OF 50W...
WEAKENING UPPER RIDGE IS IN THE MIDDLE OF THE ATLC FROM 23N49W
TO 15N39W EASTWARD TO NEAR T.D. NINETEEN THEN CONTINUING TO THE
COAST OF AFRICA NEAR GUINEA. UPPER DIFFLUENCE JUST S OF THE
RIDGE AXIS IS ALLOWING A MOSTLY LINEAR AREA OF CONVECTION TO
DEVELOP ALONG THE ITCZ...AND SIGNIFICANT OUTFLOW TO THE S OF THE
T.D. NINETEEN. DEEP-LAYERED LOW IS CENTERED WSW OF THE CANARY
ISLANDS NEAR 26N28W AND HAS PRODUCED A 1014 MB LOW AT THE
SURFACE NEAR 24N28W. WIDELY SCATTERED MODERATE CONVECTION IS
NEAR THE SFC LOW FROM 23.5N-28N BETWEEN 24W-30W ALTHOUGH
ISOLATED SHOWERS ARE ALSO EMBEDDED WITHIN THE CIRCULATION OF THE
UPPER LOW WITHIN 300 NM. FARTHER E...A SHARP UPPER RIDGE AXIS
LIES ACROSS NW AFRICA WITH DISSIPATING TSTMS OVER AND WITHIN 60
NM S OF THE CANARY ISLANDS.  UPPER DIFFLUENCE IS WEAKENING AND A
STABLE ENVIRONMENT APPEARS TO BE SETTING UP WITH NE LOW-LEVEL
FLOW.

$$
BLAKE

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