000
AXPZ20 KNHC 171528
TWDEP 

TROPICAL WEATHER DISCUSSION 
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
1605 UTC FRI APR 17 2009

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 
1530 UTC.

...ITCZ...

ITCZ AXIS IS CENTERED ALONG 07N77W TO 09N88W TO 05N100W TO 
06N110W TO 05N125W TO 05N140W. SCATTERED MODERATE CONVECTION IS 
NOTED WITHIN 70 NM S OF THE AXIS BETWEEN 92W AND 95W. SCATTERED 
MODERATE CONVECTION IS ALSO OBSERVED WITHIN 60-90 NM OF COAST OF 
COLOMBIA AND 120 NM OF COAST OF WESTERN PANAMA.

...DISCUSSION...

AT THE SURFACE...AN EARLIER QSCAT PASS SHOWED NORTHERLY WINDS OF 
20 TO 25 KT BETWEEN A 1032 MB HIGH PRES NEAR 32N132W AND THE 
BAJA COAST. SIMILAR WINDS ARE NOTED THROUGH THE SOUTHERN HALF 
OF THE GULF OF CALIFORNIA. IN FACT...SHIP 3EUS NEAR 23N108.5W IS 
REPORTING SUSTAINED WINDS OF 25 KT FROM THE NW. IN ADDITION...NW 
WINDS OF 20 KT ARE BLOWING OFF CABO CORRIENTES. LONG PERIOD 
NORTHERLY SWELL UP TO 10 FT ACCOMPANIES THE STRONG NORTHERLY 
FLOW OFF THE NORTHERN BAJA COAST.

TRADE WINDS REMAIN 20-25 KT ACROSS A LARGE PORTION OF THE AREA N 
OF THE ITCZ W OF ABOUT 115W. THESE WINDS ARE EXPECTED TO 
DIMINISH DURING THE UPCOMING WEEKEND AS HIGH PRES N OF AREA 
SHIFTS FURTHER NORTH...AND A FRONT APPROACHES THE NW CORNER. THE 
TRADE WIND CONVERGENCE COUPLED WITH A WEAK DIFFLUENT PATTERN 
ALOFT IS SUPPORTING MODEST CONVECTION TO THE NORTH OF THE ITCZ. 

GAP WINDS...
NE WINDS OF 20 KT CONTINUE TO FUNNEL THROUGH THE GULF OF 
PAPAGAYO. THIS FLOW SHOULD CONTINUE TO PULSE OVER THE NEXT FEW 
DAYS...ESPECIALLY IN THE EARLY MORNING HOURS WHEN DRAINAGE FLOW 
CONVERGENCE OFF THE LAND IS AT A MAXIMUM.

THE COMBINATION OF SOUTHERLY CROSS EQUATORIAL 15 KT FLOW AND 
WEAK DIFFLUENCE ALOFT IS AIDING A SMALL AREA OF CONVECTION ALONG 
THE ITCZ NEAR 5N95W. MODEL GUIDANCE SUGGESTS A WEAK TROUGH MAY 
BE FORMING IN THIS AREA THAT WILL PUSH WEST ALONG THE ITCZ 
THROUGH THE WEEKEND...ACCOMPANIED BY SMALL CLUSTERS OF 
CONVECTION. 

IN THE UPPER LEVELS...A RIDGE WILL DOMINATE THE EASTERN PART OF 
THE FORECAST AREA THROUGH THE WEEKEND AHEAD OF AN UPPER TROUGH 
DIGGING THROUGH THE NORTH CENTRAL PACIFIC. A CUT-OFF LOW WILL 
FORM OVER THE NW CORNER LATE SAT INTO SUN THEN MOVE OUT OF AREA 
ON MON. 

GALAPAGOS VOLCANO...
WHILE THE LA CUMBRE VOLCANO ON ISLA FERNANDINA IN THE GALAPAGOS 
ISLANDS LOCATED AT 00.4S91.5W CONTINUES TO ERUPT...THE 
GOVERNMENT OF ECUADOR REPORTS THAT THE RESULTING PLUME CONTAINS 
VAPOR AND GASES WITH NO SIGNIFICANT ASH. THE WASHINGTON VAAC HAS 
DISCONTINUED ASHFALL ADVISORIES. HOWEVER...MARINERS SHOULD STILL 
EXERCISE CAUTION AS GASES...INCLUDING SULFUR DIOXIDE...EXTEND AS 
MUCH AS 1200 NM TO THE W OF THE VOLCANO. NASA/OMI IMAGERY IS 
STILL SHOWING ELEVATED LEVELS OF SULFUR DIOXIDE IN THE AREA FROM 
FROM 01N TO 03S BETWEEN 91W AND 105W WITH A SECOND PLUME FROM 
03N TO 02S BETWEEN 112W AND 118W. EXPOSURE TO THIS GAS CAN BE 
DANGEROUS...CAUSING IRRITATION TO EYES AND SKIN.

LOOKING AHEAD...ANOTHER LATE SEASON TEHUANTEPEC EVENT WILL BE 
INDUCED BY A COLD FRONT PASSING THROUGH THE BAY OF CAMPECHE ON 
TUE FOLLOWED BY STRONG NLY WINDS. ACCORDING TO THE COMPUTER 
MODELS...A GALE FORCE WIND EVENT COULD TAKE PLACE.    

$$
GR