000
AXPZ20 KNHC 302114
TWDEP 

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
2205 UTC TUE SEP 30 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 2115 UTC.

...SPECIAL FEATURES...

LOW PRES 1009 MB IS LOCATED AT 11N97.5W...ALONG THE INTERSECTION 
OF THE ITCZ AND A TROPICAL WAVE N OF 07N ALONG 97W/98W MOVING W 
AT 7 KT. VISIBLE SATELLITE IMAGERY SHOWS CYCLONIC LOW LEVEL 
TURNING AT THE LOW CENTER. STRONG NE WINDS THROUGH THE GULF OF 
TEHUANTEPEC CONTINUE SW TO N OF THE LOW CENTER ENHANCING 
VORTICITY. THE LOW IS CENTERED ON THE EASTERN EDGE OF AN UPPER 
RIDGE THAT IS CENTERED JUST S OF BAJA CALIFORNIA...ALLOWING FOR 
EASTERLY SHEAR OVER THE AREA. THUS THE MAJORITY OF THE 
CONVECTION IS W OF THE LOW CENTER. SCATTERED MODERATE TO 
ISOLATED STRONG CONVECTION IS FROM 07N TO 13N BETWEEN 96W AND 
102W...AND FROM 12N TO 14N BETWEEN 94W AND 97W. THE SHEAR IS 
WEAK ENOUGH HOWEVER TO ALLOW FOR FURTHER DEVELOPMENT AND GLOBAL 
MODELS CONTINUE TO SUGGEST THAT THIS FEATURE WILL HOLD TOGETHER 
AS IT MOVES IN A GENERAL WESTWARD DIRECTION OVER THE NEXT FEW 
DAYS WITH A MEDIUM POTENTIAL OF IT UNDERGOING SOME SLOW 
DEVELOPMENT.

LOW PRES 1008 MB IS LOCATED AT 15N114W. A TROPICAL WAVE IS W OF 
THE LOW CENTER ALONG 117W FROM 08N TO 20N. THE WAVE/LOW COMPLEX 
IS MOVING W AT 10 KT. SCATTERED MODERATE TO STRONG CONVECTION IS 
W OF THE LOW CENTER FROM 13N TO 19N BETWEEN 114W AND 119W. SLOW 
DEVELOPMENT OF THIS SYSTEM IS POSSIBLE WITHIN THE NEXT 48 HOURS 
AS UPPER LEVEL WINDS DIMINISH.    

...TROPICAL WAVES...

TROPICAL WAVE ALONG 91W N OF 06N IS MOVING W ABOUT 10 KT. THE 
ITCZ TRAVERSES THE WAVE AXIS AS FAR N AS 12N WITH SW SURFACE 
FLOW...THAT DISRUPTS THE USUAL INVERTED-V SURFACE FLOW OF THE 
WAVE. SCATTERED MODERATE CONVECTION IS HOWEVER ON THE WAVE AXIS 
FROM 08N TO 10N BETWEEN 87W AND 92W.     

...ITCZ...

ITCZ AXIS IS CENTERED ALONG 09N80W 11N90W TO 12N96W TO 11N100W 
TO 14N110W TO 10N120W TO 12N137W TO 10N140W. BESIDES THE 
CONVECTION MENTIONED IN THE SPECIAL FEATURE AND TROPICAL WAVE 
SECTIONS... SCATTERED MODERATE CONVECTION IS S OF PANAMA FROM 
04N TO 07N BETWEEN 80W AND 84W. SCATTERED MODERATE CONVECTION IS 
FROM 13N TO 16N BETWEEN 104W AND 109W. SIMILAR CONVECTION IS 
FROM 07N TO 12N BETWEEN 110W AND 124W...AND FROM 07N TO 11N 
BETWEEN 130W AND 140W.

...DISCUSSION...

E OF 110W...20 TO 30 KT WINDS ACROSS THE GULF OF TEHUANTEPEC AND 
CONTINUE SW TO THE LOW NEAR 11N97.5W. MOST GLOBAL MODELS 
INDICATE THIS LOW TO DEVELOP...AND FOR THE GULF OF TEHUANTEPEC 
TO PERSIST FOR AT LEAST THE NEXT 2 TO 3 DAYS. ELSEWHERE S OF THE 
ITCZ MODERATE TO FRESH S TO SW CROSS EQUATORIAL FLOW PERSISTS. 
EXPECT WEAKENING EAST SHEAR OVER THE LOW NEAR 11N97.5W. ALSO 
EXPECT CONSIDERABLE POTENTIAL PRECIPITATION OVER THE AREA N OF 
05N.    

W OF 110W...DIVERGENT SE FLOW ALOFT AROUND THE SOUTHERN EDGE OF 
AN UPPER ANTICYCLONE NEAR 20N110W IS ENHANCING CONVECTION ALONG 
THE SPECIAL FEATURE ALONG 115W MENTIONED ABOVE. SLOW DEVELOPMENT 
IS EXPECTED...AS IT MOVES W WITH LESS VERTICAL WIND SHEAR. 
ELSEWHERE DEEP LAYER MOISTURE REMAINS MINIMAL OUTSIDE OF THE 
ITCZ. A WEAK 1012 MB SURFACE LOW IS CENTERED ALONG THE ITCZ NEAR 
12N137W. THIS LOW WILL CONTINUE TO FILL AS IT MOVES W. FURTHER 
TO THE NORTH...A VIGOROUS UPPER TROUGH CONTINUES TO DIG INTO 
FORECAST AREA ALONG ROUGHLY 140W N OF 15N. AN ASSOCIATED COLD 
FRONT EXTENDS FROM 32N132W TO 24N140W. SCATTEROMETER AND SHIP 
OBSERVATION SHOW A BAND OF 20 TO 25 KT SW WINDS WITHIN 150 NM E 
OF THE FRONT. THESE WINDS ARE EXPECTED TO GRADUALLY DIMINISH 
THROUGH THE NEXT COUPLE OF DAYS AS THE SUPPORTING UPPER DYNAMICS 
LIFT OUT TO THE NW. SHIP OBSERVATIONS CONFIRM THE WAVEWATCH 
MODEL SHOWING LONG PERIOD NW SWELL TO 11 FT...EXPECTED TO 
CONTINUE TO PROPAGATE INTO THE AREA GENERALLY N OF 15N W OF 125W 
THROUGH THE REMAINDER OF THE WEEK. 

$$
FORMOSA