032 
AXNT20 KNHC 191736
TWDAT 

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 
205 PM EDT MON 19 JUL 2004

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...WEATHER OBSERVATIONS...RADAR...AND METEOROLOGICAL 
ANALYSIS. 

BASED ON 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
1715 UTC.

...TROPICAL WAVES...

TROPICAL WAVE INTRODUCED OFF THE AFRICAN COAST ALONG 19W S OF 18N 
MOVING W 5-10 KT. THE DAKAR SOUNDING SHOWS A WELL-DEFINED NE/SE WIND 
SHIFT ABOUT 24 HRS AGO IN A DEEP LAYER BETWEEN 900 AND 500 MB. THE 
WAVE HAS ONLY MOVED A COUPLE OF DEGREES SINCE YESTERDAY AND IS 
CREEPING SLOWLY WWD AS IT GETS "HUNG UP" BY LOW PRES OVER 
AFRICA...BUT IT SHOULD BEGIN TO PICK UP SOME SPEED AS IT ENCOUNTERS 
THE STRONGER ATLC ELY TRADES. TSTMS ARE LOCATED E OF THE WAVE 
AXIS...CENTERED AROUND A MID-LEVEL CIRCULATION WHICH MOVED OFF THE 
AFRICAN COAST THIS MORNING. SCATTERED MODERATE CONVECTION FROM 
8N-13N BETWEEN 15W-19W.

TROPICAL WAVE LOCATED 400 NM E OF THE WINDWARD ISLANDS...OR NEAR THE 
FRENCH GUIANA/SURINAME BORDER...ALONG 54W S OF 16N MOVING W 20-25 
KT. THIS MATCHES EXTREMELY WELL WITH THE CAYENNE SOUNDING WHICH 
SHOWS A WAVE PASSAGE BETWEEN 00Z AND 12Z TODAY...BUT ONLY IN THE 
MID-LEVELS BETWEEN 400 AND 700 MB AT LATITUDE 5N. SATELLITE IMAGERY 
SHOWS A WELL-DEFINED MID-LEVEL CIRCULATION RACING TOWARDS THE SRN 
WINDWARD ISLANDS...WITH TSTMS CLUSTERED CLOSELY NEAR THE CLOUD 
CENTER. HOWEVER...THE 09Z QUIKSCAT PASS SHOWS NO LOW-LEVEL CENTER 
WITH E/NE WINDS BLOWING THROUGH THE SYSTEM. SCATTERED MODERATE 
CONVECTION FROM 9.5N-14.5N BETWEEN 55W-59W. SHOWERS/TSTMS WILL BEGIN 
TO SPREAD NWWD ACROSS THE WINDWARD ISLANDS THIS EVENING...THEN 
ACROSS THE LEEWARD ISLANDS AND ERN GREATER ANTILLES EARLY TUE 
THROUGH THU.

E CARIBBEAN TROPICAL WAVE EXTENDING FROM CENTRAL VENEZUELA TO THE 
ANEGADA PASSAGE...TILTED ALONG 4N66W 20N63W MOVING W 15 KT. THE WAVE 
HAS WEAKENED CONSIDERABLY SINCE YESTERDAY...PERTURBATION NOTED S OF 
THE VIRGIN ISLANDS...EXTENDING N OF ANGUILLA. A N/S LINE OF 
SHOWERS/TSTMS WAS MOVING OVER THE WINDWARD/LEEWARD ISLANDS THIS 
MORNING BUT HAS SINCE WEAKENED TO ISOLATED SHOWERS FROM 17N-21N 
BETWEEN 61W-62W NEAR ANTIGUA AND BARBUDA. ISOLATED SHOWERS FROM 
10N-14N BETWEEN 61W-64W.

TROPICAL WAVE OVER CENTRAL AMERICA ALONG 85W S OF 17N MOVING W 10 
KT. THE WAVE AXIS PASSED BY SAN JOSE COSTA RICA EARLY THIS MORNING 
WITH A DEEP-LAYERED WIND SHIFT EXTENDING FROM THE SURFACE TO NEAR 
300 MB. A SWIRL OF CLOUDS/CONVECTION IS NOTED MOVING ACROSS THE GULF 
OF PAPAGAYO AND NICOYA PENINSULA...WITH NO SIGNIFICANT EFFECTS 
EXTENDING NWD INTO HONDURAS. WIDELY SCATTERED MODERATE CONVECTION S 
OF 12N BETWEEN 83W-87W.

...ITCZ...

ITCZ AXIS IS ALONG 15N10W 9N24W 8N40W 12N50W...CONTINUING ALONG 
9N56W 10N70W 8N80W. SCATTERED MODERATE CONVECTION WITHIN 120 NM OF 
THE AXIS BETWEEN 23W-47W. SCATTERED MODERATE WITHIN 120 NM N OF THE 
AXIS BETWEEN 78W-82W ALONG THE N COAST OF PANAMA.

...DISCUSSION...

GULF OF MEXICO AND W ATLC...
AN UNUSUALLY STRONG DEEP-LAYERED LONGWAVE TROUGH REMAINS PLANTED 
OVER THE E HALF OF THE UNITED STATES WITH A 70-80 KT SWLY UPPER 
LEVEL JET EXTENDING FROM SOUTH CAROLINA UP THE EAST COAST TO THE 
CANADIAN MARITIMES. A COLD FRONT HAS MOVED INTO THE N GULF EXTENDING 
FROM SW GA TO 28.5N90W THEN INLAND OVER S TX WITH WIDELY SCATTERED 
MODERATE/SCATTERED WEAK CONVECTION S OF THE BOUNDARY OVER THE N GULF 
AND FL FROM 26N-30N BETWEEN 80W-94W. WIDELY SCATTERED MODERATE 
CONVECTION IS ALSO LOCATED OVER THE N BAHAMAS AND W ATLC FROM 
24N-31N BETWEEN 73W-79W. ELSEWHERE...THE ATLC SUBTROPICAL RIDGE HAS 
BEEN PUSHED FAR TO THE S...EXTENDING FROM 30N62W ACROSS THE SRN 
BAHAMAS AND CUBA TO THE YUCATAN PENINSULA WITH MOSTLY CLEAR SKIES E 
OF 74W. 

WITH THE JET NOW ON THE E SIDE OF THE TROUGH AXIS...THE TROUGH WILL 
NOT DIG ANY FARTHER S. HOWEVER...A SWD-MOVING SHORTWAVE OVER E TX/LA 
WILL SUSTAIN THE CURRENT DEPTH OF THE TROUGH AND SHOWERS/TSTMS WILL 
CONTINUE OVER THE E GULF AND FL THROUGH WED...AND OVER THE W ATLC 
THROUGH THE WEEKEND. A LARGE AREA OF MODERATE/STRONG SUBSIDENCE AND 
DRY AIR OVER THE SOUTHEAST U.S. WILL CONTINUE TO PUSH SWD BEHIND THE 
FRONT...WITH CLEARING SKIES OVER THE GULF WATERS BY WED. 

CARIBBEAN...
A LARGE AREA OF DRY MID/UPPER LEVEL AIR SPANS THE ENTIRE LENGTH OF 
THE CARIBBEAN MOVING WWD IN DEEP ELY FLOW...AND VERY LITTLE TSTM 
ACTIVITY TO SPEAK OF. A GOOD AMOUNT OF MOISTURE IS LOCATED OVER THE 
FAR SW CARIBBEAN AND CNTRL AMERICA...WHICH HAS FAVORED TSTM 
DEVELOPMENT OVER COSTA RICA AND PANAMA NEAR A TROPICAL WAVE AND THE 
ITCZ. DEEPER MOISTURE WILL BEGIN TO MOVE FROM THE ATLC OVER THE 
LESSER ANTILLES TONIGHT AND TOMORROW USHERED IN BY AN APPROACHING 
TROPICAL WAVE. HEAVY SHOWERS/TSTMS MAY DEVELOP OVER PARTS OF THE 
LEEWARD ISLANDS BEGINNING TOMORROW AND SPREAD NWWD TO PUERTO RICO 
AND THE VIRGIN ISLANDS BY WED.

REMAINDER OF SUBTROPICAL ATLC...
A LARGE MID/UPPER LOW IS LOCATED ABOUT 300 NM SE OF BERMUDA...AND 
HAS BEGUN TO MOVE SLOWLY WWD NEAR 10 KT AFTER BEING STATIONARY OVER 
THE PAST DAY OR SO. A FEW MID/HIGH LEVEL CLOUDS...WITH POSSIBLY A 
FEW ISOLATED SHOWERS...ARE LOCATED NE OF THE LOW FROM 29N-32N 
BETWEEN 56W-62W BUT OTHERWISE A LARGE AREA OF DRY AIR EXTENDS E OF 
THE LOW ACROSS THE ATLC TO AFRICA. 1023 MB SFC HIGH PRES IS CENTERED 
OVER THE E ATLC NEAR 29N37W WITH A WEAKENING SFC TROUGH EMBEDDED 
WITHIN THE RIDGE ALONG 32N40W 28N49W 28N54W. A WEAK INVERTED 
MID/UPPER LEVEL TROUGH IS COLLOCATED WITH THE SFC FEATURE...BUT 
WIDESPREAD DRY AIR IS QUICKLY ERODING ASSOCIATED CLOUDINESS. FARTHER 
E...A SMALL MID/UPPER LOW JUST MOVED EWD PAST MADEIRA ISLAND NEAR 
34N16W WITH A WEAK TROUGH AXIS EXTENDING SWWD TO 26N30W.

TROPICAL ATLC...
AN UPPER LEVEL HIGH IS CENTERED ALONG THE COAST OF MAURITANIA NEAR 
20N17W WITH A BROAD RIDGE AXIS EXTENDING SWWD INTO THE ATLC NEAR 
13N40W. MOISTURE HAS INCREASED S OF THE RIDGE AXIS WITH CONVECTION 
BECOMING MORE SCATTERED ALONG THE ITCZ PRIMARILY E OF 45W. DRY AND 
STABLE AIR REMAINS N OF THE RIDGE...EXTENDING SWD INTO THE TROPICS W 
OF 45W...EXCEPT FOR AN AREA OF MOISTURE APPROACHING THE WINDWARD 
ISLANDS ALONG A TROPICAL WAVE. JUST TO THE E...AN INVERTED UPPER 
LEVEL TROUGH EXTENDS FROM ABOUT FRENCH GUIANA NWD TO 14N49W...MOVING 
WWD WITHIN DEEP ELY FLOW.

$$
BERG