000
AXPZ20 KNHC 282139
TWDEP 

TROPICAL WEATHER DISCUSSION   
NWS NATIONAL HURRICANE CENTER MIAMI FL
2205 UTC THU APR 28 2011

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 
2100 UTC.

...ITCZ...
THE INTERTROPICAL CONVERGENCE ZONE AXIS IS ANALYZED FROM 06N77W 
TO 04N95W TO 08N108W TO 05N128W TO 02N140W. SCATTERED MODERATE 
TO ISOLATED STRONG CONVECTION IS FROM 05N TO 09N BETWEEN 111W 
AND 118W. SCATTERED MODERATE CONVECTION IS WITHIN 90 NM S OF 
AXIS W OF 138W. 

...DISCUSSION...
AN UPPER-LEVEL LOW IS APPROACHING THE FORECAST AREA FROM THE 
WEST. THE LOW IS CURRENTLY LOCATED NEAR 22N141W. ABUNDANT 
MID/UPPER LEVEL MOISTURE IS NOTED AHEAD OF THIS UPPER-LEVEL LOW 
AFFECTING THE FORECAST REGION W OF 130W. THIS SYSTEM WILL MOVE 
ACROSS THE FAR NW PORTION OF THE AREA AND WEAKEN FRI NIGHT. E OF 
125W...A BROAD UPPER-LEVEL RIDGE DOMINATES MUCH OF THE FORECAST 
WATERS. UPPER DIFFLUENCE BETWEEN THE RIDGE AND AN UPPER-LEVEL 
LOW SITUATED NEAR 4N110W IS HELPING TO MAINTAIN SCATTERED 
MODERATE TO ISOLATED STRONG CONVECTION NEAR A SURFACE TROUGH 
THAT EXTENDS ALONG 110W/111W FROM 5N TO 11N. THE RIDGE IS ALSO 
HELPING TO INDUCE SOME CONVECTION N OF THE ITCZ TO THE PANAMA 
AND COSTA RICA PACIFIC COASTS.

AN UPPER LEVEL RIDGE ALONG 145W AND N OF 30N OVER THE N CENTRAL 
PACIFIC WILL STRENGTHEN AS IT SHIFTS EAST THROUGH 48 HOURS. THIS 
WILL ACT TO REINFORCE A 1034 MB SURFACE HIGH CURRENTLY NEAR 
42N142W AS IT ALSO SHIFTS EASTWARD. AS A RESULT...EXPECT AN 
INCREASE IN WINDS AND SEAS PARTICULARLY W OF THE BAJA CALIFORNIA 
PENINSULA AND N OF 20N FRI MORNING THROUGH SAT. FRESH NW TO N 
WINDS OFF THE NORTHERN BAJA COAST WILL PERSIST AND INCREASE TO 
20 TO 25 KT THROUGH SAT. SEAS ALONG THE OFFSHORE WATERS OF THE 
UPPER BAJA PENINSULA WILL BUILD TO 14 FT IN NW SWELL IN THE AREA 
N OF 24N E OF 122W. A SMALL AREA OF FRESH TRADE WINDS IS NOTED 
ON THE SOUTHERN PERIPHERY OF THE RIDGE MAINLY FROM 04N TO 18N W 
OF 132W. MODEL GUIDANCE ALSO SUGGESTS INCREASING WINDS UP TO 25 
KT ACROSS THE GULF OF CALIFORNIA IN ABOUT 48 HOURS AS HIGH PRES 
SETTLES OVER THE GREAT BASIN.

FURTHER EAST...LIGHT AND VARIABLE WINDS CONTINUES ACROSS THE 
TROPICAL EPAC E OF 110W...WITH WEAK MONSOONAL FLOW E OF 90W. 

GAP WINDS...
A SHORT-LIVED GAP WIND EVENT IS EXPECTED THROUGH THE GULF OF 
TEHUANTEPEC. WIND FLOW TO 20 KT WILL BEGIN TONIGHT AS A WEAK 
COLD FRONT MOVES INTO THE SW GULF OF MEXICO...AND INCREASE TO 
NEAR 30 KT FRI MORNING BEFORE QUICKLY DIMINISHING BELOW 20 KT BY 
LATE FRI AS THE AIRMASS TO THE NORTH MODIFIES AND SHIFTS E. 

FRESH TRADES OVER THE SW CARIBBEAN WILL ALSO ENHANCE FLOW 
THROUGH THE GULF OF PAPAGAYO BY LATE TONIGHT AND CONTINUE INTO 
FRI.  

$$
GR