000
AXPZ20 KNHC 041000
TWDEP 

TROPICAL WEATHER DISCUSSION   
NWS NATIONAL HURRICANE CENTER MIAMI FL
1005 UTC WED MAY 04 2011

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

BASED ON 0600 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
0930 UTC.

...ITCZ...

THE INTERTROPICAL CONVERGENCE ZONE AXIS IS CENTERED ALONG 6N78W
5N90W 8N101W 7N115W 5N130W 3N140W. SCATTERED MODERATE/ISOLATED
STRONG CONVECTION EXISTS FROM 3N-10N BETWEEN 107W-117W. SCATTERED
MODERATE/ISOLATED STRONG CONVECTION IS WITHIN 60 NM N OF AXIS 
BETWEEN 80W-87W. SCATTERED MODERATE CONVECTION IS WITHIN 60 NM S 
OF AXIS BETWEEN 121W-123W.

...DISCUSSION...

AN UPPER LEVEL CYCLONE IS FILLING NEAR 27N131W WITH A NEGATIVE 
TILT TROUGH AXIS EXTENDING SE TO A BASE NEAR 21N117W. TO ITS E
BROAD MID/UPPER LEVEL RIDGING IS PRESENT TO EASTWARD OVER 
MEXICO...WITH THE ASSOCIATED ANTICYCLONE ANCHORED OVER SE
GUATEMALA NEAR 15N91W. SWLY FLOW BETWEEN THE ANTICYCLONE AND 
TROUGH IS FUNNELING EXTENSIVE UPPER LEVEL MOISTURE IN THE FORM 
OF BROKEN CIRRUS CLOUDS NNE TO ACROSS NORTHERN AND WESTERN MEXICO
N OF 19N. UPPER LEVEL DIFFLUENCE NOTED TO THE SW OF THE 
ANTICYCLONE...AND SE OF THE TROUGH CONTINUES TO AID IN THE 
DEVELOPMENT OF CONVECTION AS FOUND IN THE DEEP TROPICS GENERALLY 
S OF 13N...AND BETWEEN 95W AND 111W. BOTH THE TROUGH AND 
ANTICYCLONE WILL GRADUALLY SHIFT EASTWARD OVER THE NEXT 24 TO 48 
HOURS AS A SHORTWAVE RIDGE OVER THE FAR WESTERN PORTION FROM 
18N132W TO 26N141W SLIDES TO THE CENTRAL PORTION AS HIGHLY 
AMPLIFIED FAST MOVING RIDGE/TROUGH/RIDGE FEATURES TRACK FROM W 
TO E TO THE N OF THE DISCUSSION AREA. WLY FLOW IS NOTED OVER 
MUCH OF THE AREA S OF 20N...AND IS ADVECTING UPPER LEVEL 
MOISTURE IN THE FROM OF SCATTERED TO BROKEN CIRRUS INTO THE 
CENTRAL SECTION OF THE AREA.

OVERALL THE UPPER LEVELS ARE MOSTLY MOIST AS SEEN ON WATER VAPOR 
IMAGERY...WHILE OVER THE EASTERN PORTION OF THE AREA THE 
ATMOSPHERE IS RATHER DRY AND STABLE UNDER MODERATE SUBSIDENCE 
SEEN TO THE E OF ABOUT 95W. IN THE FAR EASTERN PORTION...THE 
TAIL END OF A CENTRAL CARIBBEAN SEA UPPER LEVEL TROUGH STRETCHES 
SW TO OVER COSTA RICA...AND TO NEAR 4N87W. THE TROUGH IS KEEPING 
ITCZ-RELATED CONVECTION TO ITS E QUITE ACTIVE. THIS TROUGH IS 
FORECAST TO CONTINUE TO MOVE EAST DURING THE NEXT 24-36 HOURS.

AT THE LOW LEVELS...FLOW IS DOMINATED BY A 1035 MB SURFACE HIGH 
WELL N OF THE DISCUSSION AREA NEAR 43N131W THAT EXTENDS A RIDGE
THROUGH 32N133W TO 25N127W TO NEAR 21N121W. THE PRES DIFFERENCE
BETWEEN THE RIDGE AND LOWER PRES TO ITS S NEAR THE ITCZ IS ENOUGH
TO INDUCE NE 20 KT TRADE WINDS N OF 8N AND W OF 130W. SEAS THERE
ARE UP TO 9 FT. THIS AREA OF TRADES IS FORECAST TO GRADUALLY 
DIMINISH OVER THE NEXT 24 TO 48 HOURS AS THE HIGH MOVES SW AND 
WEAKENS. 

A WEAK TROUGH MOVING SLOWLY W EXTENDS FROM 10N121W TO 4N123W. 
THIS TROUGH IS AIDING ITCZ CONVECTION IN ITS VICINITY. 
HOWEVER...CONVECTION THAT FORMS IS QUICKLY BEEN SHEARED BY VERY 
HOSTILE UPPER LEVEL W WINDS PRESENT S OF 20N AS STATED ABOVE.

GAP WINDS...
GULF OF TEHUANTEPEC...GALE FORCE CONDITIONS HAVE BEGUN THROUGH 
THE GULF OF TEHUANTEPEC WITH N TO NE WINDS OF 30-40 KT AND SEAS
THERE IN THE RANGE OF 11 TO 17 FT. LATEST IR SATELLITE IMAGERY 
REVEALS AN ARC CLOUD LINE LOCATED ABOUT 300 NM SSW OF THE GULF
WHILE PROPAGATING AWAY FROM IT. THIS IS A FIRST HINT THAT SUCH 
AN EVENT IS ALREADY TRACKING PLACE AS THIS FEATURE MARKS THE 
LEADING EDGE OF THE NLY WIND SURGE...MEANING THAT THE N TO NE
30-40 KT WINDS ARE ALREADY FUNNELING THROUGH THE ISTHMUS OF 
TEHUANTEPEC AND ACROSS THE GULF. THIS GAP WIND EVENT IS EXPECTED 
TO PEAK DURING TONIGHT WITH POSSIBLE MAXIMUM WINDS REACHING 40 
KT. MODEL GUIDANCE INDICATES THAT THE EVENT WILL THEN WIND DOWN 
DURING THU MORNING AND AFTERNOON AS THE STRONG RIDGE OVER 
CENTRAL AND SOUTHEASTERN MEXICO SLACKENS. EXPECT PRIMARILY NE 
SWELLS TO KEEP SEAS QUITE CHURNED UP WITH A RANGE OF 8-12 FT 
FROM 10N-13N BETWEEN 99W-104W IN 24 HOURS...AND FROM 4N-13N 
BETWEEN 92W-107W IN 48 HOURS.

GULF OF PAPAGAYO...NE TO E WINDS OF 20 TO 25 KT WILL CONTINUE TO 
PULSE THROUGH THURSDAY NIGHT IN THE AREA MARKED FROM 10N TO 12N 
AND E OF ABOUT 88W. THESE WINDS ARE FORECAST TO BE PEAK LATE AT 
NIGHT AND INTO THE EARLY MORNING HOURS.

$$
AGUIRRE