[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 071029
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
805 AM EDT THU 07 OCT 2004

TROPICAL WEATHER DISCUSSION FOR NORTH AMERICA...CENTRAL
AMERICA...GULF OF MEXICO...CARIBBEAN SEA...NORTHEASTERN
SECTIONS OF SOUTH AMERICA...AND ATLC 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
0945 UTC.

...TROPICAL WAVES...

TROPICAL WAVE ABOUT 490 NM WSW OF THE CAPE VERDE ISLANDS IS
ALONG 32W S OF 13N MOVING W 10 KT. WAVE IS LOW AMPLITUDE AT THE
BASE OF A MID/UPPER TROUGH WHICH IS PRODUCING WESTERLY SHEAR.
THIS IS PREVENTING ANY FURTHER DEVELOPMENT AND NO ASSOCIATED
DEEP CONVECTION.

TROPICAL WAVE LOCATED ABOUT 550 NM E OF BARBADOS ALONG 50W S OF
17N MOVING W 10-15 KT. WAVE IS LOW AMPLITUDE WITH A LITTLE
WESTERLY SHEAR. CLUSTERS OF SCATTERED MODERATE/ISOLATED STRONG
CONVECTION ARE FROM 10N-14N BETWEEN 45W-50W.

TROPICAL WAVE IS ALONG 59W/60W S OF 20N DRIFTING WEST. LOW LEVEL
CIRCULATION IS OBSERVED ALONG THE WAVE NEAR 16N. UPPER LEVEL
DIVERGENCE HAS FORMED WHERE THE FLOW SPLITS BETWEEN A MID/UPPER
LEVEL TROUGH TO THE W AND RIDGE TO THE E. THIS MAKES THE AXIS
PLACEMENT DIFFICULT TO DETERMINE. SCATTERED STRONG CONVECTION IS
FROM 9N-15N BETWEEN 52W-58W. LARGE CLUSTERS OF SCATTERED
MODERATE/STRONG CONVECTION ARE FROM 15N-21N BETWEEN 48W-57W.

...ITCZ...

ITCZ AXIS IS CENTERED ALONG 17N10W 8N20W 8N38W 13N48W THEN IS
DISTORTED BY THE MID/UPPER LEVEL TROUGH OVER THE CARIBBEAN AND
THE INDUCED RIDGE TO E. SCATTERED MODERATE/STRONG CONVECTION IS
WITHIN 75 NM OF LINE 7N36W-8N40W. SCATTERED MODERATE/ISOLATED
STRONG CONVECTION IS WITHIN 60 NM OF LINE 12N19W-8N23W...
12N22W-10N27W...WITHIN 45 NM OF LINE 10N27W-9N34W...AND WITHIN
75 NM OF LINE 8N40W-11N45W.

...DISCUSSION...

GULF OF MEXICO...
A 1010 MB LOW REMAINS OFF THE COAST OF MEXICO NEAR 21N96W ALONG
A STATIONARY SURFACE TROUGH WHICH IS ALSO OFF THE MEXICAN
COAST FOR THE PAST FEW DAYS. SATELLITE IMAGERY HAS SUGGESTED
THAT A LOW/MID LEVEL CIRCULATION HAS BECOME BETTER DEFINED AND
WIDESPREAD THUNDERSTORMS CONTINUE OVER MUCH OF THE W GULF.
SCATTERED STRONG CONVECTION IS WITHIN 75 NM OF LINE 21N92W-
24N97W. SCATTERED MODERATE/ISOLATED STRONG CONVECTION IS WITHIN
100 NM OF LINE 21N91W-26N94W. SCATTERED SHOWERS/THUNDERSTORMS
DOT THE REMAINDER OF THE W GULF W OF 90W. FARTHER N...A
DISSIPATING STATIONARY FRONT EXTENDS ACROSS S FLORIDA TO NE
TEXAS AS STRONG A HIGH CONTINUES TO BUILD S OVER THE SE COAST OF
THE UNITED STATES. A BROAD UPPER LEVEL HIGH IS CENTERED OVER THE
YUCATAN PENINSULA NEAR CENTRAL GUATEMALA/BELIZE WITH A RIDGE
THAT EXTENDS N OVER THE MISSISSIPPI VALLEY INTO CANADA. THIS IS
BRINGING ABUNDANT MOISTURE OVER THE W GULF ACROSS THE E GULF AND
FLORIDA JUST INTO THE W ATLC INCLUDING THE N BAHAMAS. THIS
SCENARIO WILL CONTINUE THROUGH THE WEEKEND AS THE SURFACE LOW
MOVES N AND REPLACES THE DISSIPATING STATIONARY FRONTAL BOUNDARY.

CARIBBEAN...
THE DOMINANT FEATURE OVER THE AREA CONTINUES TO BE THE LARGE
MID/UPPER LEVEL TROUGH WHICH EXTENDS FROM THE S AMERICAN COAST N
OVER THE CENTRAL/WESTERN ATLC BETWEEN THE LEEWARD ISLANDS AND
THE W CARIBBEAN E OF 75W. THE MAIN TROUGH AXIS EXTENDS ACROSS
PUERTO RICO SW TO THE GUAJIRA PENINSULA OF COLOMBIA. STRONG
SUBSIDENCE BEHIND THIS AXIS IS PRODUCING MOSTLY DRY CONDITIONS
FOR THE CARIBBEAN FROM 68W-84W WITH THE EXCEPTION OF A FEW LOW
LEVEL ISOLATED SHOWERS. ELSEWHERE...UPPER LEVEL RIDGING AND MORE
ABUNDANT MOISTURE OVER CENTRAL AMERICA CONTINUES TO PRODUCE
SCATTERED MODERATE/STRONG CONVECTION INLAND OVER BELIZE AND
GUATEMALA AND IN THE E PACIFIC REGION.

SUBTROPICAL ATLANTIC...
A MID/UPPER LEVEL TROUGH IS MOVING OFF THE E COAST OF THE UNITED
STATES WITH A WEAKENING STATIONARY FRONT ENTERING THE W ATLC
NEAR 32N65W EXTENDING SW ACROSS CENTRAL FLORIDA. THE FRONT IS
BRINGING IN GENERALLY DRY AIR MASS EXTENDING N OF PUERTO RICO
AND HISPANIOLA WITH ONLY LOW CLOUDS WITH ISOLATED SHOWERS ALONG
THE FRONTAL BOUNDARY. HOWEVER...STRONG UPPER LEVEL RIDGING IS
BUILDING OVER THE CENTRAL ATLC TO THE E OF THE DEEP TROUGH
EXTENDING TO OVER THE TROPICAL ATLC. THIS IS PUMPING A GOOD
AMOUNT OF MOISTURE N INTO THE TROPICS. A WEAK SURFACE TROUGH IS
EMBEDDED BENEATH THIS FLOW FROM 21N61W 30N57W. SCATTERED
SHOWERS/STRONG THUNDERSTORMS ARE FROM 20N-31W BETWEEN 47W-62W.
FARTHER E...A BROAD MID/UPPER TROUGH COVERS MUCH OF THE AREA E
OF 35W. MODERATE SUBSIDENCE IN THE MID/UPPER LEVELS IS KEEPING
THE AREA MOSTLY DRY.

TROPICAL ATLANTIC...
STRONG UPPER LEVEL RIDGING IS E OF THE LESSER ANTILLES FROM 15N
N INTO THE TROPICS...WITH FAIRLY SOLID WESTERLY FLOW STREAMING
E/SE S OF 15N. UPPER LEVEL DIVERGENCE HAS FORMED WHERE THESE TWO
FLOWS HAVE SPLIT...FOCUSING THUNDERSTORM ACTIVITY TO THE E OF
THE TROPICAL WAVE APPROACHING THE ISLANDS. E OF 40W... BROAD
CYCLONIC/WESTERLY FLOW EXTENDS S TO THE LATITUDE OF THE CAPE
VERDE ISLANDS...THUS CREATING A NARROW RIDGE AXIS ALONG 10N.

$$
WALLACE



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