000
AXNT20 KNHC 211134
TWDAT 

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
805 AM EDT SAT JUL 21 2012

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 0600 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
1015 UTC.

...TROPICAL WAVES...

TROPICAL WAVE OFF THE COAST OF AFRICA EXTENDS FROM 18N19W TO 
10N20W MOVING NEAR 10 KT. WAVE IS ALONG THE LEADING EDGE OF A 
SURGE OF DEEP LAYER MOISTURE AS DEPICTED ON TOTAL PRECIPITABLE 
WATER IMAGERY. A MID LEVEL CYCLONIC CIRCULATION IS AT THE BASE 
OF THE WAVE AXIS WITH NO ASSOCIATED DEEP CONVECTION.

TROPICAL WAVE APPROACHING THE LESSER ANTILLES EXTENDS FROM 
17N53W TO 8N55W MOVING W NEAR 20 KT. WAVE REMAINS EMBEDDED 
WITHIN A BROAD SURGE OF DEEP LAYER MOISTURE AS DEPICTED ON TOTAL 
PRECIPITABLE WATER IMAGERY. CLUSTERS OF SCATTERED SHOWERS/ 
ISOLATED THUNDERSTORMS ARE WITHIN 60 NM EITHER SIDE OF THE WAVE 
AXIS BETWEEN 10N-13N.

TROPICAL WAVE IN THE W CARIBBEAN EXTENDS FROM THE SE GULF OF 
MEXICO NEAR 23N85W TO 15N79W MOVING W NEAR 30 KT. WAVE REMAINS 
EMBEDDED WITHIN A BROAD SURGE OF DEEP LAYER MOISTURE AS DEPICTED 
ON TOTAL PRECIPITABLE WATER IMAGERY. WAVE IS AT THE BASE OF AN 
UPPER LOW THAT COVERS THE W ATLC...THE SE GULF OF MEXICO...AND 
THE NW CARIBBEAN. ACTIVITY IN THE VICINITY IS ASSOCIATED WITH 
THE UPPER LEVEL FEATURE.

...ITCZ/MONSOON TROUGH...

THE MONSOON TROUGH EXTENDS ACROSS AFRICA INTO THE E TROPICAL 
ATLC NEAR 23N16W TO E OF THE TROPICAL WAVE NEAR 17N19W THEN 
RESUMES W OF THE WAVE NEAR 15N21W TO 9N38W WHERE THE ITCZ 
CONTINUES ALONG 6N48W S OF THE TROPICAL WAVE APPROACHING THE 
LESSER ANTILLES TO INLAND OVER SOUTH AMERICA NEAR 7N58W. 
CLUSTERS OF SCATTERED SHOWERS/ISOLATED THUNDERSTORMS FROM 3N-8N 
BETWEEN 44W-49W.

...DISCUSSION...

GULF OF MEXICO...
A BROAD UPPER RIDGE DOMINATES ALL BUT THE FAR S GULF ANCHORED 
OFF THE COAST OF LOUISIANA. SCATTERED SHOWERS/ISOLATED 
THUNDERSTORMS ARE ACROSS THE N GULF N OF 26N BETWEEN 
APALACHICOLA BAY FLORIDA AND GALVESTON TEXAS. AN UPPER LOW IS 
CENTERED JUST S OF CENTRAL CUBA COVERING THE SE GULF INTO THE W 
ATLC AND NW CARIBBEAN WITH AN UPPER TROUGH CONTINUING W ACROSS 
THE NW CARIBBEAN AND THE YUCATAN PENINSULA TO OVER THE BAY OF 
CAMPECHE AND S MEXICO. ISOLATED SHOWERS/THUNDERSTORMS DOT THE S 
GULF S OF A LINE FROM CEDAR KEY FLORIDA ALONG 24N90W TO TAMPICO 
MEXICO INCLUDING CUBA...S MEXICO...THE STRAITS OF FLORIDA...AND 
THE BAY OF CAMPECHE. A SURFACE RIDGE EXTENDS FROM THE W ATLC 
ACROSS CENTRAL FLORIDA TO A 1019 MB HIGH NEAR 27N87W TO BETWEEN 
TAMPICO MEXICO AND BROWNSVILLE TEXAS. SURFACE RIDGE WILL REMAIN 
NEARLY STATIONARY THROUGH SUN THEN WILL DRIFT N EARLY NEXT WEEK. 
HOWEVER THE WEAK PRESSURE PATTERN WILL PERSIST ACROSS MOST OF 
THE GULF THROUGH WED. TROPICAL WAVE CURRENTLY OVER THE W 
CARIBBEAN WILL MOVE ACROSS THE FAR S GULF.

CARIBBEAN SEA...
AN UPPER LOW IS CENTERED JUST OFF THE S COAST OF CENTRAL CUBA 
COVERING THE CARIBBEAN N OF 16N W OF 74W INTO THE GULF OF MEXICO 
AND THE W ATLC GENERATING SCATTERED SHOWERS/THUNDERSTORMS N OF 
20N TO CUBA BETWEEN 80W-84W. AN UPPER RIDGE ANCHORED OVER THE 
CENTRAL ATLC COVERS THE E CARIBBEAN N OF 13N E OF 74W. CLUSTERS 
OF SCATTERED SHOWERS/ISOLATED THUNDERSTORMS ARE N OF 17N E OF 
70W INCLUDING THE E DOMINICAN REPUBLIC...PUERTO RICO...AND THE 
VIRGIN/LEEWARD ISLANDS. A SECOND UPPER RIDGE IS ANCHORED JUST S 
OF PANAMA IN THE E PACIFIC REGION. THE MONSOON TROUGH EXTENDS 
FROM COLOMBIA NEAR 9N75W ACROSS THE SW CARIBBEAN TO OVER COSTA 
RICA NEAR 10N84W GENERATING SCATTERED SHOWERS/ISOLATED 
THUNDERSTORMS ACROSS THE SW CARIBBEAN S OF 12N W OF 75W TO 
INLAND OVER COLOMBIA TO COSTA RICA. THE STRONG SURFACE RIDGE 
OVER THE ATLC IS PRODUCING A TIGHT PRESSURE GRADIENT OVER THE 
CARIBBEAN TO MAINTAIN FRESH TO STRONG TRADE WINDS AND GENERATE 
SCATTERED SHOWERS/ISOLATED THUNDERSTORMS OVER THE W CARIBBEAN 
WITHIN 60 NM ALONG THE N COAST OF JAMAICA AND FROM 14N-20N W OF 
80W TO INLAND OVER THE YUCATAN PENINSULA LEAVING THE REMAINDER 
OF THE CARIBBEAN WITH FAIR WEATHER THIS MORNING. TRADE WINDS 
WILL REMAIN ACROSS MOST OF THE REGION THROUGH WED. TROPICAL WAVE 
OVER THE W CARIBBEAN WILL W OF THE MOVE OVER CENTRAL AMERICA 
SUN. ANOTHER TROPICAL WAVE WILL ENTER THE E CARIBBEAN SUN THEN 
INTO THE W CARIBBEAN THROUGH WED.

ATLANTIC OCEAN...
THE UPPER LOW OVER THE NW CARIBBEAN EXTENDS OVER THE W ATLC W OF 
74W WHILE AN UPPER RIDGE COVERS THE REMAINDER OF THE W ATLC INTO 
THE CENTRAL ATLC AND ANCHORED IN THE CENTRAL ATLC NEAR 27N63W. 
SCATTERED SHOWERS/ISOLATED THUNDERSTORMS ARE S OF 27N W OF 74W 
TO OVER CUBA AND THROUGH THE STRAITS OF FLORIDA. CLUSTERS OF 
SCATTERED SHOWERS/ISOLATED THUNDERSTORMS ARE WITHIN 120 NM OF 
LINE FROM 15N56W ALONG 19N63W TO 19N70W THE LEEWARD/VIRGIN 
ISLANDS...PUERTO RICO...AND E DOMINICAN REPUBLIC. THE ATLC BASIN 
IS DOMINATED BY A LARGE SURFACE RIDGE ANCHORED BY A 1024 MB HIGH 
S OF THE AZORES WITH A RIDGE AXIS EXTENDING THROUGH A 1025 MB 
HIGH NEAR 32N47W ALONG 30N70W ACROSS CENTRAL FLORIDA INTO THE 
GULF OF MEXICO GIVING THE REMAINDER OF THE ATLC FAIR WEATHER 
THIS MORNING. SATELLITE IMAGERY SHOWS A PLUME OF SAHARAN DUST 
COVERING THE CENTRAL AND W ATLC FROM 20N-32N BETWEEN 50W-75W 
WITH ANOTHER PLUME COVERING THE E ATLC FROM 13N-32N E OF 40W. 
SURFACE RIDGE WILL REMAIN NEARLY STATIONARY THEN DRIFT N BY MON 
THROUGH WED.

FOR ADDITIONAL INFORMATION PLEASE VISIT
HTTP://WWW.HURRICANES.GOV/MARINE

$$
PAW