000
AXNT20 KNHC 201749
TWDAT 

TROPICAL WEATHER DISCUSSION           
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
205 PM EDT SUN AUG 20 2006

TROPICAL WEATHER DISCUSSION FOR NORTH AMERICA...CENTRAL 
AMERICA...THE GULF OF MEXICO...THE CARIBBEAN SEA...NORTHEASTERN 
SECTIONS OF SOUTH AMERICA...AND THE 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...
TROPICAL WAVE IS IN THE E ATLC ALONG 32W S OF 20N MOVING W 
20 KT. THE SFC LOW THAT WAS PREVIOUSLY ANALYZED ON THIS WAVE HAS 
BEEN DROPPED AS THE CIRCULATION APPEARS TO HAVE OPENED. BROAD 
LOW-MID LEVEL TURNING IS NOTED ABOUT THE WAVE AXIS. THIS WAVE IS 
EMBEDDED IN A REGION OF SAHARAN DUST WHICH IS LIKELY LIMITING 
ANY CONVECTION NEAR THE AXIS N OF 11N. SCATTERED MODERATE 
CONVECTION IS EMBEDDED IN THE ITCZ FROM 5N-11N BETWEEN 28W-40W. 

TROPICAL WAVE IS IN THE CNTRL ATLC ALONG 47W S OF 19N MOVING 
W 15-20 KT. THIS WAVE HAS THE STRUCTURE OF A SURGE AND APPEARS 
TO BE JUST THAT AS SAHARAN DUST IS WIDESPREAD BEHIND THE 
ANALYZED AXIS. SIMILARLY TO THE WAVE IN THE E ATLC...SHOWERS AND 
TSTMS ARE CONFINED TO THE ITCZ FROM 7N-11N BETWEEN 43W-52W.
    
TROPICAL WAVE IS IN THE E CARIBBEAN ALONG 66W S OF 18N MOVING 
W 10-15 KT. WEAK WAVE SIGNATURE IS NOTED IN THE AREA. ONLY 
ISOLATED SHOWERS ARE WITHIN 300 NM EITHER SIDE OF THE WAVE AXIS. 
MORE NUMEROUS SHOWERS EXTEND TO THE N OF THE WAVE IN THE ATLC 
ANALYZED AS A SFC TROF.
    
...THE ITCZ...
ITCZ AXIS IS CENTERED ALONG 12N15W 10N34W 9N46W 8N59W ACROSS THE 
N PORTION OF SOUTH AMERICA AND PANAMA INTO THE E PACIFIC REGION. 
BESIDES FOR THE CONVECTION ASSOCIATED WITH THE TROPICAL 
WAVES....SCATTERED MODERATE IS E OF 18W FROM 7N-13N. THIS 
ACTIVITY IS AHEAD OF THE NEXT TROPICAL WAVE TO MOVE OFF THE 
COAST OF AFRICA...THE AXIS IS WELL-DEFINED CURRENTLY ALONG 
13W/14W. SCATTERED SHOWERS AND TSTMS ARE FROM 8N-11N BETWEEN 
56W-60W.

...DISCUSSION...
GULF OF MEXICO...
SCATTERED SHOWERS AND TSTMS HAVE BECOME MORE WIDESPREAD LATE 
THIS MORNING AND EARLY AFTERNOON IN THE SE GULF FROM 24N-27N E 
OF 86W ACROSS S FLORIDA. THIS ACTIVITY IS MAINLY TRIGGERED BY 
UPPER DIFFLUENCE ON THE S SIDE OF AN UPPER LOW CENTERED ABOUT 
150 NM ESE OF TAMPA. A SMALLER DRIER UPPER LOW IS LOCATED IN THE 
W BAY OF CAMPECHE NEAR 21N97W. THE N CENTRAL AND WRN GULF IS 
COVERED BY A SPRAWLING MID-UPPER RIDGE ACROSS THE SRN U.S. AT 
THE SFC...A TROF EXTENDS FROM A 1013 MB LOW OVER SRN GEORGIA 
ACROSS THE FL PANHANDLE TO 28N90W. ISOLATED TO SCATTERED SHOWERS 
HAVE DEVELOPED WITHIN 60 NM OF THE BOUNDARY...ESPECIALLY NEAR 
THE E GULF UPPER LOW. OTHERWISE...A WEAK PRES PATTERN LIES IN 
THE REGION KEEPING WINDS LIGHT AND VARIABLE. LITTLE CHANGE IN 
THE PRES PATTERN IS EXPECTED OVER THE NEXT FEW DAYS. THE 
GREATEST CHANCE OF RAIN WILL CONTINUE TO BE IN THE E GULF THRU 
THE DAY AND TONIGHT. GFS INDICATES TROPICAL MOISTURE CURRENTLY 
IN THE SW CARIBBEAN MOVING INTO THE SE GULF ON TUE.

CARIBBEAN SEA...
THE MOST ACTIVE WEATHER IN THE AREA IS IN THE SW CARIBBEAN WHERE 
NUMEROUS SHOWERS AND TSTMS HAVE DEVELOPED FROM 11N-17N BETWEEN 
77W-81W. THIS ACTIVITY IS HIGHLY CONTRIBUTED TO UPPER DIFFLUENCE 
AT THE BASE OF A BROAD UPPER TROUGH IN THE WRN CARIBBEAN. A SFC 
TROUGH OR TROPICAL WAVE WILL BE ADDED TO THE 18Z MAP TO REFLECT 
WIND SHIFTS IN THE VICINITY SEEN AT THE SFC. SCATTERED SHOWERS 
AND TSTMS EXIST FROM 18N-20N BETWEEN 77W-84W. THE TROPICAL WAVE 
IN THE ERN CARIBBEAN IS PRODUCING VERY LITTLE SHOWER 
ACTIVITY...IN FACT BESIDES FOR THE CONVECTION OUTLINED ONLY 
ISOLATED TO SCATTERED SHOWERS DOT THE REMAINDER OF THE 
CARIBBEAN. IN THE UPPER LEVELS...A RIDGE COVERS THE ERN AND 
CENTRAL CARIBBEAN WITH WIDESPREAD DRY STABLE AIR E OF 62W. TRADE 
WINDS ARE GENERALLY 15-20 KT ACROSS THE SEA WITH THE STRONGEST 
WINDS FROM 12N TO 17N BETWEEN 68W AND 77W. GFS INDICATES TRADES 
INCREASING SLIGHTLY AND EXPANDING W OVER THE NEXT COUPLE OF 
DAYS. THE DEEP MOISTURE IN THE SW CARIBBEAN WILL MOVE TO THE WNW 
AT 10-15 KT...WHILE THE TROPICAL WAVE IN THE CNTRL ATLC 
INCREASES MOISTURE TO THE ERN ISLANDS LATE TUE.

ATLANTIC OCEAN...
AN ILL-DEFINED UPPER LEVEL PATTERN LIES ABOVE THE WRN AND CNTRL 
ATLC WITH SEVERAL UPPER LOWS EMBEDDED. THE WRN-MOST UPPER LOW IS 
CENTERED N OF THE BAHAMAS NEAR 28N78W. UPPER DIFFLUENCE ON THE S 
SIDE OF THE CIRCULATION IS ENHANCING SCATTERED SHOWERS AND TSTMS 
ACROSS THE W BAHAMAS W TO THE E GULF. ANOTHER UPPER LOW IS 
CENTERED 300 NM SE OF BERMUDA NEAR 30N61W. THIS UPPER LOW HAS A 
SFC REFLECTION AS A TROF ALONG 21N64W 29N55W. SCATTERED SHOWERS 
AND ISOLATED TSTMS ARE MAINLY WITHIN 180 NM EITHER SIDE OF THE 
TROF AXIS. ANOTHER UPPER LOW IS IN THE CNTRL ATLC NEAR 23N42W. 
THIS FEATURE IS RATHER DRY PRODUCING LITTLE WEATHER. THE E ATLC 
IS COVERED BY A MID-UPPER RIDGE WITH THE HIGH CENTER N OF THE 
CAPE VERDE ISLANDS NEAR 23N21W WITH RIDGING EXTENDING SW TO 
12N33W. MODERATE TO STRONG SUBSIDENCE LIES UNDER THE RIDGE. A 
SHIELD OF SAHARAN DUST LIES ACROSS THE ATLC E OF 48W FROM 
11N-25N...BEHIND THE CNTRL ATLC TROPICAL WAVE BASED UPON THE 
HAZY LOOK ON VISIBLE IMAGES AND CIMSS SAL TRACKING PRODUCT. 
IT IS TYPICAL FOR WAVES TO ACT HAS LEADING EDGES OF DUST 
OUTBREAKS. AT THE SFC...A SURFACE RIDGE DOMINATES THE ATLC WITH 
THE SURFACE HIGHS N OF THE REGION.

$$
CANGIALOSI