000
AXPZ20 KNHC 160935
TWDEP 

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
1005 UTC WED SEP 16 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 
0845 UTC.

...SPECIAL FEATURE...

A SURFACE LOW LIES NEAR 19N114W 1010 MB DRIFTING NW 5 KT. 
SCATTERED MODERATE TO STRONG CONVECTION IS WITHIN 100 NM OF THE 
POINT 18.5N113.5W. AN EARLIER QUIKSCAT PASS SHOWED THAT THE LOW 
IS ELONGATED NE TO SW WITH SW FLOW AT 20 TO 25 KT FEEDING 
TROPICAL MOISTURE INTO THE SYSTEM. CONDITIONS WILL REMAIN 
FAVORABLE FOR FURTHER DEVELOPMENT...AND IT COULD DEVELOP INTO A 
TROPICAL CYCLONE BEFORE REACHING COOLER WATERS IN A COUPLE OF 
DAYS.  

...TROPICAL WAVE...

TROPICAL WAVE ALONG 123W FROM 06N TO 15N MOVING WEST AROUND 10 
KT. THERE IS NO SIGNIFICANT CONVECTION ASSOCIATED WITH THE WAVE 
AT THIS TIME.

...THE ITCZ...

THE INTERTROPICAL CONVERGENCE ZONE IS ALONG THE LINE FROM 06N77W 
TO 07N105W TO 09N120W TO 08N140W. SCATTERED MODERATE WITH 
ISOLATED STRONG CONVECTION IS WITHIN 60 NM EITHER SIDE OF THE 
ITCZ AXIS W OF 125W.

...DISCUSSION...

N OF 20N...A SURFACE RIDGE...ANCHORED ON A 1020 MB HIGH PRES 
NEAR 30N128W CONTINUES TO BUILD SOUTHWARD OVER N WATERS. THE 
REGION IS MARKED BY MODERATE TO STRONG SUBSIDENCE WITH BROKEN 
STRATOCUMULUS CLOUDS COVERING THE AREA E OF 130W. PRES GRADIENT 
BETWEEN THIS RIDGE AND A SFC TROUGH OVER WESTERN MEXICO IS 
PRODUCING NW WINDS OF 20 KT AND SEAS TO 8 FT N OF 30N WITHIN 120 
NM OF THE BAJA CALIFORNIA PENINSULA. VIS SATELLITE IMAGERY IS 
STILL SHOWING A SWIRL OF LOW CLOUDS NEAR 22N140W ASSOCIATED WITH 
THE REMNANTS OF LINDA WHICH HAVE BEEN DEGRADED TO A SURFACE 
TROUGH FROM 26N138W TO 22N140W. AN EARLIER QSCAT SHOWED THE WIND 
SHIFT ASSOCIATED WITH THE TROUGH. WINDS HAVE DIMINISHED BELOW 20 
KT WITH THIS FEATURE. THE LEADING EDGE OF A COLD FRONT IS 
APPROACHING THE FAR NW CORNER OF THE AREA. A DEEP-LAYER TROUGH 
SUPPORTS THIS FRONTAL SYSTEM. THE FRONT WILL MOVE INTO NW WATERS 
OVERNIGHT AND IS EXPECTED TO DISSIPATE BY THU MORNING. 
SIGNIFICANT WAVE HEIGHTS WILL BUILD INTO THE 8 TO 10 FT RANGE IN 
NW SWELL WED AND THU OVER NW WATERS.

S OF 20N...ASIDE FROM THE AFOREMENTIONED SPECIAL FEATURE...THE 
TROPICAL WAVE...AND THE CONVECTION ALONG THE ITCZ...CONDITIONS 
ARE RELATIVELY QUIET OVER THE REMAINDER OF THE AREA. A DIFFLUENT 
PATTERN ALOFT ASSOCIATED WITH AN UPPER-LEVEL ANTICYCLONE 
CENTERED OVER WESTERN CUBA IS HELPING TO INDUCE CONVECTION OVER 
THE FAR EPAC WATERS AND ALONG THE ITCZ PARTICULARLY E OF 95W. 
ANOTHER SURFACE TROUGH IS ANALYZED NEAR 140W AND IS THE REMNANT 
OF LINDA MOVING WEST OF THE AREA. AN ASCAT PASS FROM AROUND 1900 
UTC REVEALED THE PRESENCE OF THIS FEATURE. SCATTERED MODERATE TO 
ISOLATED STRONG CONVECTION IS NOTED NEAR THE INTERSECTION OF THE 
TROUGH AND THE ITCZ AXIS.

$$
LL/GR/JSC