000
AXPZ20 KNHC 180323
TWDEP 

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
0405 UTC SAT OCT 18 2008

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.

...ITCZ...
ITCZ AXIS IS CENTERED ALONG 11N86W TO 12N93W TO 09N100W TO 
10N110W TO 09N121W TO 12N134W TO 09N140W. SCATTERED MODERATE 
CONVECTION WITHIN 120 NM S OF AXIS BETWEEN 105W AND 107W. 
SCATTERED MODERATE CONVECTION WITHIN 90 NM S OF AXIS W OF 138W. 

...DISCUSSION...
A VIGOROUS SHORTWAVE TROUGH RUSHING THROUGH THE MIDWEST WILL DIG 
INTO THE EAST CENTRAL CONUS TODAY HAS INTRODUCED A COLD FRONT 
INTO NORTHERN AND CENTRAL MEXICO AS WELL AS THE ADJACENT GULF 
WATERS. THE DIFFERENCE BETWEEN HIGH PRESSURE BUILDING BEHIND THE 
FRONT AND BROAD LOW PRESSURE EXTENDING FROM THE CENTRAL 
CARIBBEAN INTO THE MAIN DEVELOPMENT REGION OF THE TROPICAL EAST 
PACIFIC HAS RESULTED IN AN ENHANCED NORTH-SOUTH PRESSURE 
GRADIENT ACROSS THE ISTHMUS OF TEHUANTEPEC. THIS...IN TURN...HAS 
RESULTED IN THE BEGINNING OF A GAP WIND EVENT DOWSTREAM OF THE 
GULF OF TEHUANTEPEC...WITH EARLIER QUIKSCAT AND ASCAT DATA 
INDICATING WINDS OF UP TO 30 KT ALREADY. THE GAP WINDS SHOULD 
CONTINUE TO MATURE DURING THE NEXT 24 HOURS AND REACH GALE FORCE 
EARLY SUN...WITH 20 TO PERHAPS 30 KT WINDS EXPANDING SSW FROM 
THE GULF TO NEARLY 11N96.5W. SEAS SHOULD BUILD TO AS HIGH AS 11 
FT. AS HIGH PRESSURE OVER THE SOUTHERN CONUS AND MEXICO WEAKENS 
LATE SUN...WINDS SHOULD DROP BELOW GALE FORCE AND CONTINUE TO 
GRADUALLY ABATE GOING INTO MON.

ELSEWHERE...A BROAD MONSOON-TROUGH-LIKE FEATURE EXTENDS FROM THE 
NORTH CENTRAL CARIBBEAN THROUGH THE GULF OF HONDURAS AND CENTRAL 
AMERICA TO THE MAIN DEVELOPMENT REGION OF THE TROPICAL EAST 
PACIFIC. WITHIN THE TROUGH...SEVERAL SEPARATE AREAS OF LOW 
PRESSURE ARE APPARENT...ONE VERY CLOSE TO THE COAST OF BELIZE 
AND THE OTHER NEAR 12N94W. SATELLITE PICTURES SHOW A TIGHTER 
LOW- TO MID-LEVEL TURNING AT THE LATTER LOCATION AND A FAIR 
AMOUNT OF RATHER DISORGANIZED CONVECTION SCATTERED ABOUT BETWEEN 
09N AND 15N W OF 98W. GLOBAL MODELS PERSIST THE CONVECTION AND 
SURFACE LOW NEAR 12N94W AND MOVE IT SLOWLY W TO WNW OVER THE 
NEXT FEW DAYS...WITH NO SIGNS OF APPRECIABLE DEVELOPMENT. THE 
PRESENCE OF BOTH SYSTEMS AND DEEP EASTERLIES ALOFT IN AN 
UNSTABLE ENVIRONMENT SUGGESTS THE POTENTIAL FOR FREQUENT AND 
PERSISTENT HEAVY RAINS FROM CENTRAL AMERICA THROUGH MUCH OF 
SOUTHERN MEXICO...WITH THE THREAT OF POSSIBLE FLOODING AND 
MUDSLIDES. 

FINALLY...LONG PERIOD NW SWELL COMING OUT OF THE NORTH CENTRAL 
AND NORTH PACIFIC IS ON THE DECREASE BUT STILL COVERS MUCH OF 
THE NW HALF OF THE DISCUSSION AREA. MEANWHILE...TO THE SW...A 
NEW GROUP OF LONG PERIOD SW SWELL FROM THE SUBTROPICAL AND 
MID-LATITUDE SOUTHERN HEMISPHERE IS ARRIVING OVER THE SOUTHERN 
HALF OF THE DISCUSSION AREA AND WILL BE ON THE INCREASE THIS 
WEEKEND.  EXPECT SEAS TO BUILD UP TO 8 TO 10 FT ACROSS THE 
REGION AND PEAK LATE SUN AND MON.

$$
KIMBERLAIN