000
AXPZ20 KNHC 182106
TWDEP 

TROPICAL WEATHER DISCUSSION     
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
2205 UTC TUE SEP 18 2007

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 
2045 UTC.

...SPECIAL FEATURE...

TROPICAL DEPRESSION TWELVE-E CENTERED NEAR 13.6N 107.9W AT 
18/2100 UTC MOVING WNW AT 10 KT. ESTIMATED MINIMUM CENTRAL 
PRESSURE IS 1006 MB. MAXIMUM SUSTAINED WIND SPEED HAS INCREASED 
TO 30 KT WITH GUSTS TO 40 KT. SEE LATEST NHC FORECAST/ADVISORY 
UNDER AWIPS/WMO HEADERS MIATCMEP2/WTPZ22 KNHC FOR MORE DETAILS. 
THIS SYSTEM HAS BECOME BETTER ORGANIZED THROUGHOUT THE DAY. THE 
CLOUD STRUCTURE IS INCREASINGLY CIRCULAR AND ASSOCIATED DEEP 
CONVECTION HAS EXPANDED AND GAINED CURVATURE. SCATTERED MODERATE 
TO STRONG IS IN BANDED STRUCTURES WITHIN 210 NM N AND 90 NM S 
SEMICIRCLES. STRENGTHENING IS FORECAST IN THE SHORT TERM. 

...TROPICAL WAVES...
TROPICAL WAVE ALONG 122W FROM 7N TO 20N MOVING W 10-15 KT. THE 
1009 MB LOW ANALYZED ALONG THE WAVE AXIS EARLIER HAS BEEN 
DROPPED FROM THE ANALYSIS BASED ON VISIBLE IMAGERY. 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. A 
MID-LEVEL SYSTEM...VORTICITY MAXIMUM...APPEARS TO BE FUELING 
THIS CONVECTION ALONG THE ITCZ W OF THE WAVE AXIS.

...ITCZ...
ITCZ AXIS CENTERED ALONG 10N84W 8N95W 11N105W 14N120W 15N130W 
10N140W. SCATTERED MODERATE CONVECTION IS FROM 8N TO 12N BETWEEN 
87W AND 92W. SCATTERED MODERATE IS FROM 9N TO 11N BETWEEN 116W 
AND 120W. NUMEROUS STRONG IS FROM 12N TO 17N BETWEEN 123W AND 
138W. 

...DISCUSSION...

THE TROPICAL BELT REMAINS SOMEWHAT ACTIVE W OF 105W ENHANCED BY 
THE TROPICAL DEPRESSION AND A TROPICAL WAVE. THESE ARE DISCUSSED 
ABOVE. THE OTHER LOW PRES SYSTEM PREVIOUSLY ANALYZED NEAR 
14N130W HAS BEEN DROPPED FROM THE SFC ANALYSIS BASED ON QSCAT 
AND VIS IMAGES WHICH INDICATE LITTLE SFC TURNING. HOWEVER 
...EVEN THOUGH THIS SYSTEM IS NOT AT THE SFC THERE IS STILL GOOD 
VORTICITY HELPING TO SUSTAIN CONVECTION WITHIN THE ITCZ. THE 
LARGER SCALE PRES PATTERN ACROSS THE SUBTROPICS IS DOMINATED BY 
A 1030 MB HIGH CENTERED NW OF THE AREA NEAR 39N152W. THE 
TIGHTENED GRADIENT BETWEEN THIS HIGH AND LOW PRES TROUGHING 
ALONG THE ITCZ IS MAINTAINING STRONG NELY TRADES W OF ABOUT 125W.

IN THE MID AND UPPER LEVELS...A WEAKENING UPPER LOW IS PULLING 
OFF TO THE NE CENTERED NEAR 32N136W. AN UPPER RIDGE LIES FURTHER 
SE PARKED NEAR 22N124W. 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 BELOW 20 KT WITHIN THE NEXT 24 HOURS.

$$
CANGIALOSI