000
AXPZ20 KNHC 291625
TWDEP 

TROPICAL WEATHER DISCUSSION    
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
1605 UTC TUE MAY 29 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 
1600 UTC.

...SPECIAL FEATURES...

TROPICAL STORM ALVIN IS CENTERED NEAR 12.6N 114.2W AT 29/1500 
UTC MOVING W AT 4 KT. ESTIMATED MINIMUM CENTRAL PRESSURE IS 1004 
MB. MAXIMUM SUSTAINED WIND SPEED IS 35 KT WITH GUSTS TO 45 KT. 
SEE THE LATEST NHC FORECAST/ADVISORY UNDER AWIPS HEADER 
MIATCMAT1 FOR MORE DETAILS. NUMEROUS MODERATE TO STRONG 
CONVECTION REMAINS MOST CONSOLIDATED NEAR AND WITHIN 90 NM IN 
THE ERN SEMICIRCLE. CONVECTION IS MORE SCATTERED IN NATURE TO 
THE W OF THE CENTER. SOME INTENSIFICATION...TO A MID-GRADE 
TROPICAL STORM...IS EXPECTED OVER THE NEXT DAY OR TWO AS THE 
OCEANIC ENVIRONMENT REMAINS FAVORABLE AND THE SHEAR IS MODERATE. 

A LARGE AREA OF LOW PRES...ANALYZED 1009 MB NEAR 14N98W OR ABOUT 
200 NM SSW OF THE GULF OF TEHUANTEPEC...HAS BECOME BETTER 
ORGANIZED. THIS SYSTEM IS BEING MONITORED FOR FURTHER 
DEVELOPMENT AND A TROPICAL DEPRESSION MAY FORM DURING THE NEXT 
DAY OR SO. THIS SYSTEM MAY POSE AS A RAIN THREAT FOR MEXICO AS 
ITS MOISTURE SPREADS OVER COASTAL PORTIONS BETWEEN THE GULF OF 
TEHUANTEPEC AND ACAPULCO LATER TODAY OR TONIGHT. CURRENTLY 
...SCATTERED MODERATE CONVECTION IS MOST ORGANIZED IN A BANDED 
STRUCTURE WITHIN 120 NM IN THE S SEMICIRCLE.

...ITCZ...

ITCZ AXIS IS CENTERED ALONG 11N84W 15N93W 8N111W 8N126W 6N140W. 
SCATTERED MODERATE CONVECTION IS WITHIN 90 NM S OF AXIS BETWEEN 
87W-91W. CLUSTERS OF SCATTERED MODERATE ARE WITHIN 60 NM EITHER 
SIDE OF THE AXIS BETWEEN 121W-132W.

DISCUSSION...
A SHARP UPPER TROUGH IS PULLING INTO THE W PORTION OF THE 
DISCUSSION AREA WITH THE AXIS EXTENDING FROM AN UPPER LOW NEAR 
29N132W SW ALONG 20N140W AND THEN S OF THE HAWAIIAN ISLANDS. A 
SPRAWLING UPPER RIDGE IS CENTERED ACROSS THE TROPICS STRETCHING 
E-W ALONG 17N E OF 130W WITH SEVERAL SMALL UPPER HIGHS 
EMBEDDED IN THE RIDGE. AN UPPER JET LIES BETWEEN THESE FEATURES 
ORIGINATING NEAR THE BASE OF THE TROUGH AND EXTENDING NE ALONG 
16N140W 24N129W THEN BENDING E FROM 27N118W AND ACROSS THE SRN 
HALF OF BAJA CALIFORNIA. THIS JET IS ONLY PICKING UP A SWATH OF 
MID-HIGH LEVEL CLOUDS AND CARRYING IT WITHIN 180 NM TO ITS S AND 
E. WHILE ENHANCED CONFLUENCE ALOFT IS PROVIDING A VERY STABLE 
ENVIRONMENT N AND W OF THE JET. 

THE UPPER ATMOSPHERE ALOFT IN THE TROPICS IS ALSO MARGINALLY 
STABLE UNDER THE INFLUENCE OF THE UPPER RIDGE. HOWEVER...BOTH 
T.S. ALVIN AND THE AREA OF LOW PRES TO IT'S E HAVE BEEN ABLE TO 
SUSTAIN A FAIR AMOUNT OF CONVECTION THRU THE DAY SO FAR.

AT THE SFC...THE PRES GRADIENT IS WEAK AS A COLD FRONT 
...ASSOCIATED WITH THE UPPER TROUGH MENTIONED ABOVE...NEARS THE 
NW PORTION OF THE AREA BREAKING DOWN THE SUBTROPICAL HIGH. THIS 
HAS ALLOWED WINDS TO BE LIGHT ACROSS MUCH OF THE REGION N AND W 
OF TROPICAL STORM ALVIN. 

$$
CANGIALOSI