000
AXPZ20 KNHC 212148
TWDEP 

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
2205 UTC SUN SEP 21 2008

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

BASED ON 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
2100 UTC.

...SPECIAL FEATURES...

A BROAD LOW PRESSURE SYSTEM IS LOCATED JUST OFF THE MEXICAN 
COAST NEAR 17N102W. 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 NUMEROUS MODERATE SCATTERED STRONG CONVECTION FROM 16N 
TO 19N BETWEEN 101W AND 105W.

...TROPICAL WAVES...

A TROPICAL WAVE ALONG 87W N OF 09N INTO CENTRAL AMERICA IS 
MOVING W ABOUT 10 KT. A BROAD AREA OF CYCLONIC TURNING AT THE 
LOW LEVELS IS EVIDENT IN THE LATEST VISIBLE SATELLITE IMAGERY. 

A TROPICAL WAVE ALONG 121W/122W FROM 05N TO 16N IS MOVING W 5 TO 
10 KT. A 1011 MB LOW IS ATTACHED TO THE WAVE AT 12N. 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 09N84W TO 10N100W TO 09N110W TO 
12N121W TO 09N140W. SCATTERED MODERATE CONVECTION IS LOCATED 
FROM 180 TO 360 NM S OF THE AXIS BETWEEN 86W AND 89W. SCATTERED 
MODERATE ISOLATED STRONG CONVECTION IS LOCATED WITHIN 90 NM N OF 
THE AXIS BETWEEN 122W AND 126W. SCATTERED MODERATE CONVECTION IS 
LOCATED WITHIN 120 NM N AND 180 NM S OF THE AXIS BETWEEN 132W 
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 18Z RUN OF 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 1026 MB HIGH CENTERED NEAR 
35N143W TO 30N130W TO 20N112W.

E OF 105W...
EASTERLY WINDS ALOFT COVER THE AREA E OF 105W WITH THE STRONGEST 
FLOW LOCATED S OF 08N TO THE EQUATOR. 

$$
CAB