000
AXPZ20 KNHC 211530
TWDEP 

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
1605 UTC SUN SEP 21 2008

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

BASED ON 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
1500 UTC.

...SPECIAL FEATURES...

A BROAD LOW PRESSURE SYSTEM IS LOCATED JUST OFF THE MEXICAN 
COAST NEAR 16N100W. THIS SYSTEM HAS BECOME SLIGHTLY LESS 
ORGANIZED OVER THE PAST 24 HOURS. NEVERTHELESS IT MAY DEVELOP 
INTO A TROPICAL CYCLONE OVER THE NEXT TWO DAYS AT IT TRACKS WNW. 
LOCALLY HEAVY RAINS ARE POSSIBLE ALONG THE MEXICAN COAST 
OVER THE NEXT COUPLE OF DAYS. THE LATEST SATELLITE IMAGERY 
INDICATES SCATTERED MODERATE TO STRONG CONVECTION N OF 14N 
BETWEEN 100W AND 106W. 

...TROPICAL WAVES...

A TROPICAL WAVE ALONG 88W N OF 07N INTO CENTRAL AMERICA IS 
MOVING W ABOUT 15 KT. A BROAD AREA OF CYCLONIC TURNING AT THE 
LOW LEVELS IS EVIDENT IN EARLY MORNING VISIBLE SATELLITE 
IMAGERY. MOST OF THE DEEP CONVECTION IS LOCATED ALONG AND W OF 
THE NICARAGUA AND COSTA RICA COASTLINES.

A TROPICAL WAVE ALONG 123W FROM 05N TO 16N IS MOVING W 5 TO 10 
KT. LOW-LEVEL CYCLONIC TURNING IS APPARENT WITHIN 3 TO 4 DEGREES 
EITHER SIDE OF THE WAVE AXIS FROM 08N TO 16N. CONVECTION IS TIED 
TO THE ITCZ AND LOCATED W OF THE WAVE AXIS.

...ITCZ...

ITCZ AXIS IS CENTERED ALONG 10N85W TO 11N100W TO 09N110W TO 
11N118W TO 09N140W. SCATTERED MODERATE TO STRONG CONVECTION IS 
LOCATED WITHIN 240 NM EITHER SIDE OF THE AXIS BETWEEN 84W AND 
89W. SCATTERED MODERATE TO STRONG CONVECTION IS LOCATED WITHIN 
120 NM EITHER SIDE OF THE AXIS BETWEEN 113W AND 126W. SCATTERED 
MODERATE CONVECTION IS LOCATED WITHIN 180 NM EITHER SIDE OF THE 
AXIS BETWEEN 136W AND 140W.

...DISCUSSION...

W OF 105W...
A WELL-DEFINED MIDDLE/UPPER LEVEL RIDGE CUTS EAST-WEST ACROSS 
THE DISCUSSION AREA W OF 105W WITH THE AXIS POSITIONED ALONG 
16N/17N. THIS FEATURE HAS MOVED LITTLE OVER THE PAST DAY OR SO. 
WATER VAPOR LOOP INDICATES STRONG SUBSIDENCE N OF THE RIDGE TO 
JUST BEYOND 32N. WINDS AT 300 MB FROM THE GFS MODEL INDICATE 
WESTERLY WINDS FROM 30 TO 35 KT FROM 22N TO 28N E OF 140W ACROSS 
BAJA CALIFORNIA AND ARE EXPECTED TO STRENGTHEN OVER THE NEXT 24 
TO 48 HOURS AS THE RIDGE MOVES SLOWLY N. OVER THE TROPICS S OF 
THE RIDGE SATELLITE CLOUD DRIFT WINDS INDICATE EASTERLY TO 
NORTHEASTERLY WINDS ALOFT AND MEASURE 15 TO 25 KT FROM 08N TO 
15N AND UP TO 15 KT HIGHER S OF 08N TO THE EQUATOR. AT THE 
SURFACE A TROUGH IS LOCATED ALONG 140W FROM 07N TO 14N AND A 
RIDGE AXIS EXTENDS FROM A 1025 MB HIGH CENTERED NEAR 35N143W TO 
30N130W TO 18N112W.

E OF 105W...
EASTERLY WINDS ALOFT COVER THE AREA E OF 105W WITH THE STRONGEST 
FLOW LOCATED S OF 08N TO THE EQUATOR. A 1215Z QUIKSCAT PASS 
INDICATES SOUTHWESTERLY TO WESTERLY WINDS OF 10 TO 15 KT OVER 
MOST OF THE AREA E OF 105W. 

$$
CAB