000
AXPZ20 KNHC 181653 AAA
TWDEP 

TROPICAL WEATHER DISCUSSION...UPDATED      
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
1605 UTC TUE SEP 18 2007

TROPICAL WEATHER DISCUSSION FOR THE EASTERN PACIFIC OCEAN
FROM THE EQUATOR TO 32N...EAST OF 140W. 

BASED ON 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
1500 UTC.

UPDATED TO INCLUDE NEWLY FORMED TROPICAL DEPRESSION.

...SPECIAL FEATURE...

TROPICAL DEPRESSION TWELVE-E CENTERED NEAR 13.4N 107.9W AT 
18/1700 UTC MOVING WNW AT 9 KT. ESTIMATED MINIMUM CENTRAL 
PRESSURE IS 1007 MB. MAXIMUM SUSTAINED WIND SPEED IS 25 KT WITH 
GUSTS TO 35 KT. SEE LATEST NHC FORECAST/ADVISORY UNDER AWIPS/WMO 
HEADERS MIATCMEP2/WTPZ22 KNHC FOR MORE DETAILS. THIS SYSTEM HAS 
BECOME BETTER ORGANIZED OVER THE MORNING HOURS WHICH WAS THE 
REASON FOR ISSUING THE SPECIAL ADVISORY. THE CLOUD STRUCTURE IS 
NOW MUCH MORE CIRCULAR AND ASSOCIATED DEEP CONVECTION HAS 
INCREASED AND GAINED CURVATURE. SCATTERED MODERATE TO STRONG IS 
IN A BAND WITHIN 180 NM N SEMICIRCLE. STRENGHTENING IS FORECAST. 

...TROPICAL WAVES...
TROPICAL WAVE ALONG 119W FROM 9N TO 19N MOVING W 10-15 KT. A 
1009 MB LOW IS ANALYZED ALONG THE WAVE AXIS NEAR 15N. MUCH OF 
THE ASSOCIATED CONVECTION IS SHEARED WELL TO THE W OF THE WAVE 
AXIS BY STRONG NE TO ELY UPPER FLOW ON THE S SIDE OF AN UPPER 
HIGH. THE EXCEPTION IS A SMALL AREA OF SCATTERED SHOWERS AND 
TSTMS WITHIN 90 NM OF THE WAVE S OF 12N.

...ITCZ...
ITCZ AXIS CENTERED ALONG 9N84W 13N104W 15N125W 10N140W. 
SCATTERED MODERATE ISOLATED STRONG IS WITHIN 140 NM N OF AXIS 
FROM 86W TO 90W. NUMEROUS STRONG FROM 13N TO 17N BETWEEN 121W 
AND 135W. 

...DISCUSSION...

THE TROPICAL BELT REMAINS SOMEWHAT ACTIVE W OF 105W WITH THREE 
LOW PRES SYSTEMS ANALYZED. TWO OF THESE ARE DISCUSSED ABOVE. THE 
SYSTEM THAT HAS THE BEST CHANCE TO DEVELOP IS THE SPECIAL 
FEATURE WHICH COULD BE A TROPICAL DEPRESSION LATER TODAY. THE 
OTHER LOW PRES SYSTEM IS LOCATED NEAR 14N130W MOVING W ABOUT 10 
KT OVER THE PAST 24 HOURS. IT IS CHALLENGING TO DETERMINE THE 
LOW LEVEL CENTER ON NIGHT CHANNEL VIS IMAGES DUE TO ABUNDANT 
DEEP CLOUDINESS OBSCURING THE LOW-LEVEL SIGNATURE. THIS LOW 
COUPLED WITH CONVERGENCE NEAR THE ITCZ IS GENERATING SCATTERED 
MODERATE/ISOLATED STRONG WITHIN 210 NM W OF THE LOW. THE LARGER 
SCALE PRES PATTERN ACROSS THE SUBTROPICS IS DOMINATED BY A 1030 
MB HIGH CENTERED NW OF THE AREA NEAR 38N151W. THE TIGHTENED 
GRADIENT BETWEEN THIS HIGH AND LOWS ALONG THE ITCZ HAVE BEEN 
MAINTAINING STRONG NELY TRADES W OF ABOUT 125W.

IN THE MID AND UPPER LEVELS...AN UPPER LOW CENTERED NEAR 31N138W 
IS DRIFTING N. AN UPPER RIDGE FURTHER SE IS PARKED NEAR 21N124W. 
THIS HIGH IS PROVIDING NE/ELY SHEAR OVER THE TROPICS W OF 115W. 
A SHORT WAVE TROUGH EXTENDS SWD INTO THE TROPICS FROM NEW MEXICO 
TO SOUTHERN BAJA. WATER VAPOR IMAGERY SHOWS A MOISTURE PLUME 
EXTENDING ACROSS THE AREA S OF 20N. DRY STABLE AIR DOMINATES THE 
REMAINDER OF THE REGION.

GAP WINDS...A HI-RES QSCAT PASS AROUND 12Z THIS MORNING REVEALED 
20-25 KT WINDS IN THE GULF OF TEHUANTEPEC...THIS IS ABOUT 5-10 
KT LIGHTER THAN THE PASS ABOUT 24-H AGO. THIS GAP EVENT IS 
ANTICIPATED TO DECREASE OVER THE NEXT 24-48 HOURS.

$$
CANGIALOSI