000
AXPZ20 KNHC 210316
TWDEP 

TROPICAL WEATHER DISCUSSION      
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
0405 UTC SAT JUL 21 2007

TROPICAL WEATHER DISCUSSION FOR THE EASTERN PACIFIC OCEAN
FROM THE EQUATOR TO 32N...EAST OF 140W. 

BASED ON 0000 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
0300 UTC.

...TROPICAL WAVES...

TROPICAL WAVE 96W/97W S OF 16N MOVING W 10 KT WITH A 1009 MB LOW 
ALONG THE AXIS NEAR 11N96W. THE LOW-LEVEL CENTER NOTED EARLIER 
IN VISIBLE IMAGERY HAS NOW BEEN COVERED BY THE EDGES OF A DEEP 
CONVECTIVE CLUSTER AND UPPER LEVEL CIRRUS. ALSO WITHIN THE PAST 
6 HRS...THE CONVECTIVE ORGANIZATION HAS CHANGED SUCH THAT THE 
STRONGEST ACTIVITY IS BECOMING CLUSTERED NEAR THE CENTER WITH 
POSSIBLE BANDING INSTEAD OF SURROUNDING IT BY MORE THAN 100 NM 
AWAY FROM THE CENTER. SCATTERED MODERATE/STRONG CONVECTION FROM 
9N-13N BETWEEN 95W-99W. SCATTERED MODERATE FROM 6N-16N BETWEEN 
100W-106W.

TROPICAL WAVE ALONG 122W S OF 16N MOVING W 15 KT. THE WAVE IS 
EMBEDDED WITHIN THE EXTENDED NE/SW ORIENTED ITCZ AXIS...AND 
THERE IS NO CLEAR INDICATION OF ITS EXACT POSITION. SHOWERS/ 
TSTMS ORIENTED ALONG THE ITCZ.

...ITCZ...

ITCZ AXIS IS CENTERED ALONG 8N77W 10N96W 6N103W THEN FROM 
20N109W 10N120W 5N135W 9N140W. SCATTERED MODERATE/ISOLATED 
STRONG CONVECTION WITHIN 120 NM OF AXIS BETWEEN 78W-88W. 
SCATTERED MODERATE 60 NM OF AXIS BETWEEN 113W-119W. WIDELY 
SCATTERED SHOWERS/TSTMS ELSEWHERE WITHIN 120 NM OF AXIS BETWEEN 
107W-135W.

...DISCUSSION...

E OF 105W...
SEE TROPICAL WAVES FOR CONVECTIVE DISCUSSION ON SURFACE LOW SSW 
OF THE GULF OF TEHUANTEPEC. THE SYSTEM LIES JUST W OF A SMALL 
UPPER LEVEL TROUGH ALONG 92W AND THE WIND SHEAR PRODUCT FROM 
UW-CIMSS INDICATES THAT THERE IS ABOUT 15 KT OF NORTHEASTERLY 
VERTICAL SHEAR OVER THE LOW...WITH THE STRONGEST SHEAR LOCATED 
ABOUT 10 DEG W OF THE TROPICAL WAVE. AS A RESULT OF THE 
FAVORABLE ENVIRONMENT...THE SYSTEM APPEARS TO BE GAINING SOME 
ORGANIZATION. ELSEWHERE...AN UPPER RIDGE AXIS LIES ACROSS THE 
SRN CARIBBEAN ALONG 11N AND PROTRUDES WWD ACROSS COSTA RICA AND 
NICARAGUA TO 10N90W. UPPER DIFFLUENCE ON THE IMMEDIATE S SIDE OF 
THE RIDGE AXIS IS HELPING CONVECTION TO FORM ALONG THE ITCZ WITH 
SOME OF THE ACTIVITY AFFECTING PANAMA AND COSTA RICA. FARTHER 
N...A STRONG UPPER HIGH OVER NE MEXICO NORTHEASTERLY STEERING 
FLOW OVER MUCH OF SRN MEXICO. AS A RESULT...MANY OF THE TSTMS 
WHICH FORMED OVER THE MEXICAN MOUNTAINS ARE NOW MAKING THEIR WAY 
TO THE PACIFIC COAST BETWEEN ACAPULCO AND MANZANILLO.

W OF 105W...
THE MOST STRIKING FEATURE AT THE MOMENT IS THE NWD EXTENSION OF 
THE ITCZ WHICH STRETCHES FROM 6N130W IN THE DEEP TROPICS NE TO 
THE COAST OF MEXICO ROUGHLY NEAR MAZATLAN. BROAD S/SW FLOW FEEDS 
INTO THE AXIS WITH MOISTURE BEING DRAWN NWD INTO SRN PARTS OF 
THE GULF OF CALIFORNIA. AS A RESULT...SCATTERED SHOWERS ARE 
MOVING INLAND FROM MAZATLAN NWD INTO NW MEXICO. A MID/UPPER LOW 
LOCATED JUST W OF BAJA CALIFORNIA NEAR 25N115W IS ALSO HELPING 
TO PULL THE DEEP TROPICAL MOISTURE NWD TOWARDS LAND. ELSEWHERE 
THE WEATHER IS QUITE TRANQUIL. AN UPPER TROUGH ALONG THE W COAST 
OF THE UNITED STATES HAS WEAKENED THE SUBTROPICAL RIDGE AND THUS 
THE TRADES ARE CURRENTLY IN A WEAKENED STATE.

$$
BERG