000
AXPZ20 KNHC 210907
TWDEP 

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
1005 UTC SUN SEP 21 2008

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

BASED ON 0600 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
0900 UTC.

...SPECIAL FEATURES...

A BROAD LOW PRESSURE SYSTEM IS CENTERED A COUPLE HUNDRED NM SE 
OF ACAPULCO MEXICO NEAR 14N97W. THIS SYSTEM SHOWED SOME SIGNS OF 
ORGANIZING EARLIER TONIGHT...BUT OVER THE PAST SEVERAL HOURS THE 
ASSOCIATED CONVECTION HAS BECOME STRETCHED AND SHAPELESS. THE 
LOW-LEVEL CENTER...IF THERE IS ONE...IS CHALLENGING TO LOCATE.  
MY BEST GUESS IS NEAR THE SOUTHERN EDGE OF BROKEN CONVECTION 
WHICH LIES N OF 14N BETWEEN 94W AND 102W. IR IMAGERY AND DOPPLER 
RADAR DATA FROM PUERTO ANGEL MEXICO SHOWS SOME AREAS OF HEAVY 
RAINS OVER THE PACIFIC COAST OF MEXICO...MAINLY BETWEEN THE GULF 
OF TEHUANTEPEC TO JUST W OF ACAPULCO. DUE TO THE SLOW MOTION OF 
THIS SYSTEM AND CLOSE PROXIMITY TO LAND...CONTINUED LOCALLY 
HEAVY RAINS ARE POSSIBLE ACROSS THESE AREAS OVER THE NEXT COUPLE 
OF DAYS. 

...TROPICAL WAVES...

TROPICAL WAVE IS OVER PORTIONS OF CENTRAL AMERICA ALONG 86W N OF 
06N MOVING W 15-20 KT. WELL DEFINED CYCLONIC TURNING IS EVIDENT 
IN THE LOW-LEVEL CLOUDS ACROSS THE CARIBBEAN PORTION OF THE 
WAVE. THE INTERACTION WITH A NARROW INVERTED UPPER TROUGH IS 
CAUSING SCATTERED MODERATE TO STRONG CONVECTION WITHIN 240 NM OF 
THE WAVE AXIS OVER THE EPAC WATERS. 

TROPICAL WAVE ALONG 97W/98W N OF 06N IS ASSOCIATED WITH THE 
SPECIAL FEATURE ABOVE.

TROPICAL WAVE PREVIOUSLY ALONG 108W HAS BEEN DROPPED FROM THE 
SFC ANALYSIS AS IT HAS NOT BE TRACKABLE FOR SEVERAL DAYS. BASED 
ON A 3-4 DAY SATELLITE LOOP...IT APPEARS THAT MUCH OF THE WAVE 
WAS ABSORBED BY THE BROAD NEARLY STATIONARY LOW PRESSURE SYSTEM 
(SPECIAL FEATURE).

TROPICAL WAVE ALONG 122W FROM 04N TO 15N IS DRIFTING W. THIS 
FEATURE HAS CHANGED AND MOVED LITTLE OVER THE PAST COUPLE OF 
DAYS. LOW-LEVEL CYCLONIC TURNING IS APPARENT WITHIN 300-400 NM 
OF THE WAVE AXIS. CONVECTION IS CONFINED TO THE INTERSECTION OF 
THE ITCZ. 

...ITCZ...

ITCZ AXIS IS CENTERED ALONG 10N85W TO 11N95W TO 09N110W TO 
11N120W TO 09N140W. SCATTERED MODERATE TO STRONG CONVECTION IS 
WITHIN 240 NM EITHER SIDE OF THE AXIS BETWEEN 84W AND 90W. 
SCATTERED MODERATE CONVECTION IS WITHIN 180 NM S OF THE AXIS 
BETWEEN 113W AND 125W.

...DISCUSSION...

W OF 110W...
MID TO UPPER RIDGING CENTERED NEAR 17N130W AND ASSOCIATED 
ABUNDANT DRY STABLE AIR DOMINATES THE PATTERN ALOFT. THE 
ATMOSPHERE IS MOST STABLE OVER THE NE AND NW WATERS WHERE UPPER 
CONFLUENCE IS NOTED DUE TO A PAIR OF TROUGHS N AND W OF THE 
ZONE. IN THE LOWER LEVELS...THE TIGHTENED PRESSURE GRADIENT NEAR 
THE BAJA COAST IS PRODUCING N TO NW 20 KT WINDS N OF 25N E OF 
120W...AS REVEALED BY 03Z QSCAT PASS. SIMILAR MAGNITUDE NE 
TRADES ARE OCCURRING OVER THE FAR SW WATERS FROM 11N-15N W OF 
133W ENHANCED BY A WEAK LOW-LEVEL TROUGH ALONG 143W. 

E OF 110W...
A LARGE MID TO UPPER HIGH OVER SOUTHERN MEXICO IS PRODUCING NE/E 
UPPER FLOW ACROSS MUCH OF THIS PORTION OF THE EPAC. WHILE 
WIDESPREAD MOISTURE IS APPARENT ON WATER VAPOR IMAGERY...DEEP 
CONVECTION IS MAINLY TIED TO THE TROPICAL WAVE ALONG 86W AND 
SPECIAL FEATURE NOTED ABOVE. THE LAST COUPLE SCATTEROMETER 
PASSES MISSED THE BROAD LOW PRES AREA...BUT BASED ON A PARTIAL 
PASS...20 KT WINDS ARE POSSIBLE NEAR THE ILL-DEFINED LOW AND 
GENERALLY 15-20 KT SW WINDS S OF THE ITCZ BETWEEN 94W AND 101W.

$$
CANGIALOSI