000
AXNT20 KNHC 210605
TWDAT 

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
205 AM EDT FRI AUG 21 2009

TROPICAL WEATHER DISCUSSION FOR NORTH AMERICA...CENTRAL 
AMERICA...GULF OF MEXICO...CARIBBEAN SEA...NORTHERN SECTIONS
OF SOUTH AMERICA...AND ATLANTIC OCEAN TO THE AFRICAN COAST
FROM THE EQUATOR TO 32N. THE FOLLOWING INFORMATION IS BASED
ON SATELLITE IMAGERY...METEOROLOGICAL ANALYSIS...WEATHER 
OBSERVATIONS...AND RADAR.

BASED ON 0000 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
0345 UTC.

...SPECIAL FEATURES...
HURRICANE BILL IS CENTERED NEAR 25.5N 64.9W OR ABOUT 405 NM S OF 
BERMUDA AND ABOUT 805 NM SE OF CAPE HATTERAS NORTH CAROLINA 
MOVING NW AT 16 KT. THE LATEST MINIMUM CENTRAL PRESSURE JUST 
REPORTED BY AN AIR FORCE RESERVE HURRICANE HUNTER AIRCRAFT IS 
951 MB. MAXIMUM SUSTAINED WIND SPEED IS 105 KT WITH GUSTS TO 130 
KT. SEE THE LATEST FORECAST/ADVISORY UNDER AWIPS/WMO HEADERS 
TCMAT3/WTNT23 KNHC FOR MORE DETAILS. SCATTERED MODERATE/ISOLATED 
STRONG CONVECTION IS WITHIN 120 NM OF THE CENTER IN THE E 
SEMICIRCLE WITH SCATTERED MODERATE CONVECTION COVERING THE 
REMAINDER OF THE AREA FROM 23N-29N BETWEEN 58W-63W. 

...TROPICAL WAVES...
TROPICAL WAVE IS ALONG 25W/26W S OF 16N MOVING W NEAR 10 KT. 
WAVE IS BEGINNING TO LAG THE DEEP LAYER MOISTURE MAXIMUM 
OBSERVED IN TOTAL PRECIPITABLE WATER IMAGERY BUT STILL RETAINS 
THE LOW/MID LEVEL CURVATURE. THIS WAVE REMAINS WITHIN AN AREA OF 
RATHER DRY UPPER AIR WITH SCATTERED SHOWERS WITHIN 30 NM OF 
14.5N FROM 24W-27W. 

TROPICAL WAVE REMAINS TILED EXTENDING FROM 16N54W TO 8N50W 
MOVING W 15-20 KT. WAVE REMAINS EMBEDDED WITHIN AN AREA DEEP 
LAYER MOISTURE MAXIMUM OBSERVED IN TOTAL PRECIPITABLE WATER 
IMAGERY AND IS WELL DEFINED IN THE LOW/MID LEVELS. HOWEVER...DUE 
TO RATHER DRY UPPER AIR THERE IS ONLY ISOLATED SHOWERS WITHIN 30 
NM OF 12.5N FROM 51W-57W. 

TROPICAL WAVE THAT WAS ALONG 90W WAS RELOCATED TO ALONG 94W/95W 
S OF 19N MOVING W 10-15 KT BASED ON A LOW/MID LEVEL ROTATION IN 
THE E PACIFIC REGION AS OBSERVED ON SATELLITE IMAGERY. ISOLATED 
SHOWERS ARE ALONG THE IMMEDIATE COAST OF MEXICO S OF 19N FROM 
93W-94W. 

...THE ITCZ...
THE ITCZ AXIS IS CENTERED ALONG 13N16W 9N35W 11N48W 9N55W 
10N62W. CLUSTERS OF SCATTERED MODERATE/STRONG CONVECTION ARE 
WITHIN 60 NM OF 12N FROM 27W-30W. CLUSTERS OF SCATTERED 
MODERATE/ISOLATED STRONG CONVECTION ARE FROM 10N-15N E OF 22W TO 
INLAND OVER W AFRICA...FROM 7N-10N BETWEEN 28W-34W...AND WITHIN 
90 NM OF THE ITCZ AXIS FROM 44W-59W. 

...DISCUSSION...

GULF OF MEXICO...
AN UPPER RIDGE EXTENDS FROM OVER CENTRAL MEXICO NE ALONG THE 
COAST OF TEXAS ACROSS THE LOWER MISSISSIPPI VALLEY TO THE 
CAROLINAS PROVIDING UPPER DIFFLUENCE ACROSS THE N GULF TO 
GENERATE SCATTERED SHOWERS/ISOLATED THUNDERSTORMS N OF 27N E OF 
93W AND WITHIN 60 NM ALONG THE COAST OF THE FLORIDA PENINSULA N 
OF THE FLORIDA KEYS. THE SURFACE RIDGE FROM THE W ATLC CONTINUES 
TO BUILD ACROSS THE E GULF. THE REMAINDER OF THE GULF IS 
TRANQUIL TONIGHT AS CLEAR SKIES PREVAIL. 

CARIBBEAN SEA...
AN UPPER LOW REMAINS OVER THE YUCATAN NEAR 17N89W COVERING THE 
NW CARIBBEAN. AN UPPER RIDGE EXTENDS FROM E PANAMA TO E CUBA 
ALONG 78W PROVIDING UPPER LEVEL DIFFLUENCE TO GENERATE SCATTERED 
SHOWERS/ISOLATED THUNDERSTORMS S OF 12N FROM COLOMBIA TO 
NICARAGUA. FRESH TO STRONG EASTERLY TRADE WINDS CONTINUE ACROSS 
THE AREA. DRY STABLE AIR IS ACROSS THE REMAINDER OF THE AREA E 
OF 80W LIMITING ANY DEEP LAYERED SHOWERS. HOWEVER...SOME LOW 
LEVEL ISOLATED SHOWERS ARE ACROSS THE NE CARIBBEAN N OF 17N E OF 
74W ACROSS HISPANIOLA...PUERTO RICO AND THE VIRGIN ISLANDS. 

ATLANTIC OCEAN...
THE MAIN FOCUS FOR THE ATLC CONTINUES TO BE HURRICANE BILL. 
NORTHERLY UPPER FLOW COVERS THE W ATLC W OF HURRICANE BILL AS A 
WEAK UPPER LOW IS MOVING TOWARD THE BAHAMA ISLANDS NEAR 27N74W 
GENERATING ISOLATED SHOWERS S OF 28N E OF 70W. OTHERWISE THE 
ATLC BASIN IS DOMINATED BY A SURFACE RIDGE ANCHORED BY A WEAK 
1018 MB HIGH OVER THE SE US AND IN THE E ATLC BY A 1030 MB HIGH 
NEAR THE AZORES WITH A WEAKNESS OVER THE CENTRAL ATLC DUE TO 
HURRICANE BILL. 

$$
WALLACE