000
AXNT20 KNHC 181038
TWDAT 

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
805 AM EDT WED JUL 18 2007

TROPICAL WEATHER DISCUSSION FOR NORTH AMERICA...CENTRAL 
AMERICA...THE GULF OF MEXICO...THE CARIBBEAN SEA...NORTHERN 
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...METEOROLOGICAL ANALYSIS... 
WEATHER OBSERVATIONS...AND RADAR.

BASED ON 0600 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
1015 UTC.

...TROPICAL WAVES...
TROPICAL WAVE IS SLIGHTLY TITLED ALONG 20N28W THROUGH A 1011 MB 
LOW NEAR 15N30W 9N31W MOVING W NEAR 20 KT. BROAD WELL DEFINED 
CIRCULATION ASSOCIATED WITH THE SURFACE LOW COVERING THE AREA 
FROM 11N-22N BETWEEN 27W-37W. NO ASSOCIATED DEEP CONVECTION. 

TROPICAL WAVE IS SLIGHTLY TILTED ALONG 18N54W 10N57W 3N57W 
MOVING W NEAR 20 KT. BROAD WAVE WITH LOW/MID LEVEL INVERTED-V 
CURVATURE COVERING THE AREA FROM 50W-65W. SCATTERED MODERATE/ 
ISOLATED STRONG CONVECTION IS WITHIN 90/120 NM OF LINE FROM 
15N52W TO THE COAST OF SOUTH AMERICA NEAR 11N63W INCLUDING THE 
WINDWARD ISLANDS...TRINIDAD AND TOBAGO. 

TROPICAL WAVE IS ALONG 84W S OF 19N MOVING W NEAR 20 KT. WAVE IS 
MOSTLY INLAND OVER CENTRAL AMERICA JUST TO THE E OF AN UPPER 
RIDGE ENHANCING SCATTERED MODERATE/ISOLATED STRONG CONVECTION 
FROM 14N-17N BETWEEN 82W-85W. 

...THE ITCZ...
ITCZ AXIS IS CENTERED ALONG 14N15W 15N22W 10N27W 7N41W 12N56W 
9N63W. SCATTERED MODERATE/STRONG CONVECTION IS WITHIN 120/150 NM 
OF THE AXIS FROM 43W-49W. SCATTERED MODERATE/ISOLATED STRONG 
CONVECTION IS WITHIN 60/75 NM OF THE AXIS FROM 28W-36W AND 
WITHIN 120 NM OF LINE FROM 10N49W TO 11N54W. CLUSTERS OF SIMILAR 
CONVECTION ARE FROM 6N-10N BETWEEN 50W-61W AND WITHIN 120 NM 
ALONG THE COAST OF AFRICA FROM 7N-10N. 
 
...DISCUSSION...
GULF OF MEXICO...
BROAD UPPER LEVEL LOW IS CENTERED OVER N/CENTRAL MEXICO COVERING 
TEXAS AND MEXICO N OF 21N. AN UPPER LEVEL RIDGE EXTENDS FROM S 
MEXICO ACROSS THE BAY OF CAMPECHE AND THE W GULF TO THE N GULF 
COAST NEAR 29N95W ENHANCING SCATTERED SHOWERS/THUNDERSTORMS S OF 
28N W OF 88W AND INDUCING A SURFACE TROUGH THAT EXTENDS ROUGHLY 
E/W FROM 25N88W ALONG 24N94W TO 22N98W. ANOTHER UPPER RIDGE 
EXTENDS FROM AN UPPER HIGH OFF THE E COAST OF THE FLORIDA 
PENINSULA TO OVER THE E GULF ENHANCING SCATTERED SHOWERS/ 
ISOLATED THUNDERSTORMS OVER S OF 28N E OF 88W. OTHERWISE A 
SURFACE RIDGE IS BEGINNING TO WEAKEN AND EXTENDS ALONG 29W/30N 
FROM THE W ATLC TO TEXAS. 

CARIBBEAN SEA...
THE UPPER RIDGE OVER THE W GULF OF MEXICO EXTENDS OVER THE FAR W 
CARIBBEAN W OF 87W. A CUT-OFF UPPER LOW REMAINS CENTERED OVER 
THE CAYMAN ISLANDS NEAR 19N80W COVERING THE AREA N OF 15N FROM 
73W-85W GENERATING SCATTERED SHOWERS/ISOLATED THUNDERSTORMS N OF 
17N FROM 80W-85W. AN UPPER RIDGE EXTENDS FROM OVER COLOMBIA/ 
PANAMA BORDER NW TO CENTRAL AMERICA NEAR 14N83W. THIS UPPER 
RIDGE COMBINED WITH THE ITCZ AXIS EXTENDING ACROSS S PANAMA AND 
COSTA RICA ARE GENERATING SCATTERED SHOWERS/THUNDERSTORMS S OF 
11N E OF 82W TO INLAND OVER COLOMBIA AND PANAMA. WEAK UPPER HIGH 
IS IN THE W TROPICAL ATLC E OF THE LEEWARD ISLANDS EXTENDING A 
RIDGE AXIS E ACROSS THE LEEWARD ISLANDS TO 15N72W AND IS BEING 
ECLIPSED BY THE TROPICAL WAVE E OF THE LESSER ANTILLES. DRY 
STABLE AIR COVERS THE E CARIBBEAN E OF 80W EXCEPT IN THE REGION 
OF THE WINDWARD ISLANDS WHERE THERE IS CONVECTION ASSOCIATED 
WITH THE TROPICAL WAVE. MODERATE/STRONG EASTERLY TRADE WINDS 
CONTINUE ACROSS THE CARIBBEAN. 

ATLANTIC OCEAN...
AN UPPER HIGH OFF THE E COAST OF THE FLORIDA PENINSULA NEAR 
28N79W AND COVERS THE W ATLC N OF 25N W OF 70W. THE CUT-OFF 
UPPER LOW OVER THE CAYMAN ISLANDS COVERS THE SW ATLC S OF 25N W 
OF 74W GENERATING SCATTERED SHOWERS/ISOLATED THUNDERSTORMS S OF 
30N W OF 78W ACROSS S FLORIDA INTO THE E GULF OF MEXICO. AN 
ELONGATED UPPER LOW IS NEAR 28N65W COVERING THE AREA N OF 23N 
FROM 60W-68W WITH A WEAK SURFACE TROUGH EXTENDING FROM 32N61W TO 
THE MONA PASSAGE GENERATING SCATTERED SHOWERS/ISOLATED 
THUNDERSTORMS WITHIN 120/150 NM OF LINE FROM 19N67W 25N63W TO 
32N61W. WEAK UPPER HIGH IS IN THE W TROPICAL ATLC E OF THE 
LEEWARD ISLANDS NEAR 18N61W EXTENDING A RIDGE AXIS E INTO THE 
CARIBBEAN AND NE TO 27N58W ENHANCING THE ABOVE SHOWER/ 
THUNDERSTORM ACTIVITY. WEAK NARROW UPPER TROUGH EXTENDS INTO THE 
N/CENTRAL ATLC ALONG 32N33W TO 23N45W BUT THE ASSOCIATED 
LOW/FRONTAL BOUNDARY ARE N OF THE REGION. ANOTHER UPPER RIDGE 
EXTENDS OFF THE COAST OF AFRICA OVER THE E ATLC E OF 30W. THE 
FIRST VISIBLE IMAGES OF THE DAY SHOW A LARGE SURGE OF AFRICAN 
DUST CONTINUING OVER THE E ATLC S OF A LINE FROM THE STRAIT OF 
GIBRALTAR 35N12W 30N22W 23N50W WITH SOME CLEARING S OF 14N E OF 
26W. THERE IS A TROPICAL WAVE/LOW IS EMBEDDED WITHIN THIS DUST. 
THE REMAINDER OF THE ATLC CONTINUES TO BE DOMINATED BY A SURFACE 
RIDGE ANCHORED BY A 1029 MB HIGH CENTERED N OF THE REGION NEAR 
36N50W AND EXTENDS TO OVER THE N GULF OF MEXICO. 

$$
WALLACE