000
AXPZ20 KNHC 240954
TWDEP 

TROPICAL WEATHER DISCUSSION 
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
1005 UTC SAT OCT 24 2009

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 
0915 UTC.

...TROPICAL LOW...
AN ELONGATED LOW TO MID LEVEL TROUGH PERSISTS EARLY THIS MORNING 
FROM THE TROPICAL EPAC NEAR 09N89W NE ACROSS COSTA RICA AND INTO 
THE EXTREME SW CARIBBEAN...THEN NNE ACROSS JAMAICA...EAST 
CENTRAL CUBA AND ON THROUGH THE NW BAHAMAS. A VIGOROUS UPPER 
LEVEL CYCLONE CENTERED OVER EASTERN CUBA WAS HELPING TO DEEPEN 
THE NORTHERN EXTENSION OF THIS TROUGH. ACROSS THE EPAC. LATE 
AFTERNOON VISIBLE IMAGERY YESTERDAY SHOWED A SMALL CYCLONIC 
SWIRL NEAR 09N87W...ON THE FAR W END OF THIS TROUGH. 
OVERNIGHT...CONVECTION OCCURRING ON THE S SIDE OF THIS TROUGH IN 
THE EPAC HAS MERGED AND CONGEALED INTO A MODEST SIZED CLUSTER 
OVER AND JUST TO THE E OF THIS SURFACE LOW...PREVIOUSLY ANALYZED 
AT 1007 MB. UPPER DIVERGENCE ACROSS THIS AREA IS HELPING TO 
SUSTAIN DEEP CONVECTION ACROSS THE LOW TO THE W COAST OF COSTA 
RICA...AND IS EXPECTED TO CONTINUE THROUGH TONIGHT. THIS MAY 
ALLOW FOR SOME IMPROVED ORGANIZATION OF THE LOW. SEVERAL OTHER 
CYCLONIC LOW TO MID LEVEL SWIRLS WERE EVIDENT OVERNIGHT ALONG 
THE ELONGATED TROUGH...ON BOTH SIDE OF CENTRAL AMERICA. 

...ITCZ...
THE INTERTROPICAL CONVERGENCE ZONE AXIS EXTENDS 09N76W TO 08N84W 
TO 13N108W TO 09N140W. SCATTERED MODERATE WITHIN 120 NM OF AXIS 
BETWEEN 95 AND 105W...AND W OF 110W. 

...DISCUSSION...
A L/W UPPER TROUGH DOMINATES THE N HALF OF THE AREA TODAY... 
EXTENDING FROM THE WESTERN GREAT LAKES SW THROUGH CENTRAL TEXAS 
AND NORTHERN MEXICO THEN NEARLY WWD ALONG 24N...WHERE A FEW 
WAVES HAVE BEGUN TO DEVELOP WITHIN THE TROUGH AXIS...THEN TO A 
LARGE UPPER CYCLONE CENTERED NEAR 19N145W. THE BASE OF THE UPPER 
TROUGH IS BROAD AND RELATIVELY FLAT YIELDING WNW TO WSW UPPER 
LEVEL FLOW FROM 15N TO 25N BETWEEN 130W AND THE W COAST OF 
MEXICO. S OF THIS WLY FLOW ALOFT...NARROW UPPER LEVEL RIDGING 
EXTENDED NEARLY W TO E ALONG ABOUT 10N...AND DIRECTLY OVER THE 
ITCZ WHERE IT WAS ACTING TO VENTILATE CONVECTION NICELY. THE 
LARGE UPPER CYCLONE E OF THE HAWAIIAN ISLANDS WAS PRODUCING 
ANTICYCLONIC AND STRONGLY DIVERGENT FLOW OVER THE ITCZ BETWEEN 
145W AND 130W...WHERE SST'S ARE ANOMALOUSLY WARM...AND WHERE 
CONVECTION HAS BEEN VERY ACTIVE UNTIL THE PAST FEW HOURS. A 
NARROW AND ELONGATED UPPER RIDGE WAS SANDWICHED BETWEEN THE SE 
SIDE OF THE N AMERICAN L/W TROUGH AND THE UPPER LOW OVER 
CUBA...AND EXTENDED FROM AN UPPER HIGH ALONG THE E COAST OF THE 
YUCATAN PENINSULA TO THE GULF OF TEHUANTEPEC.       

AT THE LOW LEVELS A 1028 HIGH WAS CENTERED N OF THE AREA NEAR 
35N138W WITH A RIDGE EXTENDING SE TO NEAR 20N114W. THE GRADIENT 
NE OF THE RIDGE IS SUPPORTING NORTHERLY WINDS 20-25 KT FROM THE 
COAST OF CENTRAL CALIFORNIA DUE S INTO THE FORECAST AREA W OF 
122W...WHICH MERGES WITH THE WIND FIELD PRODUCED BY GRADIENT SE 
THROUGH SW OF THE RIDGE...ALSO NE TRADES AT 20 TO 25 KT. N TO NW 
AND SOUTHERN HEMI S TO SW SWELLS ARE MERGING OVER THE 
SUBTROPICAL WATERS PRODUCING AREAS OF CONFUSED SEAS. SEAS WILL 
GENERALLY BE ON A SUBSIDING TREND DURING THE NEXT 24 HOURS.

$$
STRIPLING