000
AXPZ20 KNHC 180335
TWDEP 

TROPICAL WEATHER DISCUSSION      
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
0405 UTC TUE SEP 18 2007

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 
0330 UTC.

...SPECIAL FEATURES...

AN AREA OF LOW PRES...ASSOCIATED WITH A TROPICAL WAVE ALONG 106W 
FROM 6N TO 17N...IS ANALYZED WITH 1009 MB CENTERED NEAR 
13N106W.  SCATTERED MODERATE CONVECTION IS FROM 12 TO 15N 
BETWEEN 103W AND 108W.  A TROPICAL DEPRESSION COULD FORM DURING 
THE NEXT COUPLE OF DAYS AS IT MOVES WESTWARD AT 10 KT.

...TROPICAL WAVES...

TROPICAL WAVE IS ALONG 117W FROM 8N TO 20N IS MOVING WWD 5-10 
KT.  CONVECTION IS CONFINED TO THE ITCZ.  THE WAVE IS BEING 
SHEARED BY MODERATE NE TO ELY UPPER FLOW. 

A 1010 MB LOW IS CENTERED NEAR 14N128W ALONG THE ITCZ.  
SCATTERED MODERATE TO ISOLATED STRONG CONVECTION IS OVER A LARGE 
AREA FROM 12N TO 17N BETWEEN 121W AND 134W 

...ITCZ...

ITCZ AXIS IS CENTERED ALONG 11N85W 9N95W 13N106W 12N110W 16N120W 
10N140W. BESIDES FOR CONVECTION ASSOCIATED WITH THE SPECIAL 
FEATURE AND TROPICAL WAVES...SCATTERED MODERATE IS FROM 8N TO 
11N BETWEEN 100W AND 103W.  

...DISCUSSION...
AT THE SFC...MODERATE SUBTROPICAL RIDGING IS IN PLACE EXTENDING 
SW FROM A 1028 MB HIGH CENTER LOCATED NW OF THE AREA NEAR 
38N150W.  THE MAIN FEATURES ARE THE TROPICAL WAVES AND SURFACE 
LOWS DISCUSSED ABOVE.  A TIGHTENED PRESSURE GRADIENT BETWEEN THE 
SUBTROPICAL HIGH AND LOWS ALONG THE ITCZ IS ENHANCING NE TRADES 
ACROSS THE W PORTION OF THE REGION. 

IN THE MID AND UPPER LEVELS...AN UPPER LOW IS DRIFTING NW 
CENTERED NEAR OUR NW CORNER NEAR 30N138W.  AN UPPER LEVEL HIGH 
IS FURTHER E CENTERED NEAR 21N120W.  THIS HIGH IS RESPONSIBLE 
FOR PROVIDING THE NE/ELY SHEAR OVER THE TROPICAL WAVE ALONG 
117W.  A SHARP SHORTWAVE TROUGH EXTENDS SWD FROM THE WRN U.S. 
ACROSS NW MEXICO.  IN THE TROPICS A MOISTURE PLUME EXTENDS FROM 
8N TO 20N BETWEEN 80W AND 140W.  DRY STABLE AIR DOMINATES THE 
REMAINDER OF THE REGION N OF 20N AND W OF 110W ENHANCED BY A 
SOMEWHAT CONFLUENT PATTERN.

$$
FORMOSA