000
AXPZ20 KNHC 282209
TWDEP 

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
2205 UTC SUN MAY 28 2006

TROPICAL WEATHER DISCUSSION FOR THE EASTERN PACIFIC OCEAN FROM 
THE EQUATOR TO 32N...EAST OF 140W. THE FOLLOWING INFORMATION IS 
BASED ON SATELLITE IMAGERY...WEATHER OBSERVATIONS...RADAR...AND 
METEOROLOGICAL ANALYSIS.

BASED ON 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
2145 UTC.

...SPECIAL FEATURE...

TROPICAL STORM ALETTA IS ESTIMATED NEAR 15.8N 101.0W AT 2100 
UTC. THIS POSITION IS ABOUT OR ABOUT 105 MILES...170 
KM...SOUTHWEST OF ACAPULCO MEXICO. ALETTA IS NEARLY STATIONARY 
OR DRIFTING SLOWLY N AT 2 KT. ESTIMATED MINIMUM CENTRAL PRESSURE 
IS 1002 MB. MAXIMUM SUSTAINED WIND SPEED IS 40 KT WITH GUSTS TO 
50 KT. NUMEROUS MODERATE TO STRONG WITHIN 150 NM  OVER E 
SEMICIRCLE. STRONG W SHEAR IS CONTINUING TO SUPPRESS CONVECTION 
OVER THE W SEMICIRLE. SEE LATEST NHC FORECAST/ADVISORY UNDER 
AWIPS/WMO HEADERS MIATCMEP1/WTPZ21 KNHC FOR MORE DETAILS. 

...TROPICAL WAVES...

A TROPICAL WAVE ALONG 93W N OF 2N HAS MOVED W 10 KT THE PAST 72 
HOURS. SCATTERED MODERATE AND ISOLATED STRONG CONVECTION NOTED 
WITHIN 60 NM OF THE WAVE AXIS AT 7N

..ITCZ...

ITCZ AXIS IS CENTERED ALONG...7N78W 7N93W 13N104W 7N120W 3N140W. 
SCATTERED MODERATE ISOLATED STRONG FROM 2N TO 10N E OF 99W AND 
WITHIN 120 NM EITHER SIDE OF LINE 13N101W 13N112W 7N122W AND 
WITHIN 90 NM EITHER SIDE OF LINE 5N134W 5N140W.

...DISCUSSION...

AN UPPER CYCLONE IS NEARLY STATIONARY OVER THE NW CONUS. A  
NEGATIVE TILT SHORTWAVE TROUGH EXTENDS SSE INTO THE DISCUSSION 
AREA ALONG 32N114W TO A BASE OVER COASTAL OLD MEXICO AT 
18N104W...JUST NW OF THE TROPICAL STORM. DRY UPPER AIR IS 
INDICATED ALONG A 300 NM WIDE BAND DEFINED BY POINTS 18N150W 
24N130W 29N103W. ANOTHER BAND OF DRY AIR IS INDICATED WITHIN 180 
NM EITHER SIDE OF LINE 10N122W 20N114W WHERE IT MERGES WITH THE 
PREVIOUSLY DESCRIBED AREA. AT THE LOW LEVELS A RIDGE EXTENDS 
ALONG 30N140W TO 13N100W WITH SCATTERED TO BROKEN STRATOCUMULUS 
N OF 12N W OF 118W.

AN UPPER ANTICYCLONE IS QUASI STATIONARY NEAR 10N115W WITH ITS 
ENVELOPE OF ANTICYCLONIC FLOW DOMINATING THE DISCUSSION AREA N 
OF THE ITCZ TO 22N BETWEEN 140W AND 110W TO ANOTHER SMALL 
ANTICYCLONE NOTED NEAR 12N106W...WITH ITS RIDGE EXTENDING E TO A 
CREST AT 12N96W. DEBRIS MOISTURE FROM ITCZ CONVECTION W OF 133W 
IS ADVECTED NE AND REMAINS UNDER THE RIDGE W OF 120W. UPPER 
DIFFLUENCE UNDER THE RIDGE TO THE E OF 120W IS ENHANCING 
CONVECTION ALONG THE ITCZ BETWEEN 120W AND 104W...BUT THE DEBRIS 
MOISTURE REMAINS UNDER THE UPPER RIDGE. A RIDGE ALSO EXTENDS NE 
FROM THE ANTICYCLONE AT 12N106W ACROSS THE TROPICAL STORM 
CRESTING OVER THE GULF OF MEXICO ALONG POINTS 25N100W 27N89W.

AN UPPER ANTICYCLONE IS CENTERED OVER S AMERICA AT 6S74W WITH A 
RIDGE EXTENDING NW ACROSS THE EQUATOR AT TO A CREST AT 9N95W. 
UPPER DIFFLUENCE UNDER THE RIDGE IS ALSO ENHANCING CONVECTION 
ALONG THE ITCZ BETWEEN 98W AND 76W BUT THE DEBRIS MOISTURE 
REMAINS IN ROUGHLY THE SAME AREA TO THE N BUT IS SPREADING S AND 
EVENTAUULAY EVAPORATING ALONG THE EQUATOR BETWEEN 80W AND 102W. 

$$
NELSON