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Eastern Pacific Tropical Weather Discussion (Text)



000
AXPZ20 KNHC 311547
TWDEP 

TROPICAL WEATHER DISCUSSION...CORRECTED                                     
NWS NATIONAL HURRICANE CENTER MIAMI FL                         
1605 UTC TUE MAR 31 2015

CORRECTED FOR DISCUSSION INFORMATION

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 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
1500 UTC. 

...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH...

THE ITCZ AXIS EXTENDS FROM 05N120W TO 07N126W TO BEYOND 05N140W. 
A SECOND AND WELL DEFINED ITCZ AXIS IS NOTED SOUTH OF THE 
EQUATOR FROM 03.4S90W TO 02S100W TO 3.4S110W. SCATTERED MODERATE 
CONVECTION IS S OF THE EQUATOR BETWEEN 92W AND 104W. SIMILAR 
CONVECTION IS ALSO OBSERVED FROM 05N TO 10N BETWEEN 120W AND 
128W...AND FROM 05N TO 08N BETWEEN 117W AND 119W.

DURING MARCH AND APRIL...THE MONSOONAL CIRCULATION OVER THE 
TROPICAL NE PACIFIC IS NOT PRESENT...AND OCCASIONALLY BREAKS 
DOWN WITH CONVERGENCE NOTED ON EACH SIDE OF THE EQUATOR IN WHAT 
IS REFERRED TO AS A DOUBLE ITCZ STRUCTURE. AS PREVIOUSLY 
MENTIONED A SECOND ITCZ IS SEEN S OF THE EQUATOR ON THE 1200 UTC 
SURFACE MAP. THE PRESENCE OF AN ACTIVE SOUTHERN ITCZ IS FORECAST 
TO PERSIST OVER THE NEXT 24-48 HOURS. 

...DISCUSSION...

A RIDGE COVERS THE NORTHERN WATERS MAINLY N OF 17N W OF 118W. 
SOUTH OF THE RIDGE...THE PRES GRADIENT BETWEEN THE HIGH AND 
LOWER PRES ALONG THE ITCZ IS RESULTING IN FRESH NE TRADEWINDS 
FROM 14N TO 18N W OF 135W...WHERE SEAS ARE 8-9 FT IN MIXED NE 
AND NW SWELL. A DISSIPATING FRONTAL BOUNDARY IS CLIPPING THE FAR 
NW CORNER OF THE AREA AND CURRENTLY EXTENDS FROM 30N135W TO 
BEYOND 28N140W. STRONGER HIGH PRES IN THE WAKE OF THE FRONT 
MOVING EASTWARD WILL THEN DOMINATE THE NORTHERN FORECAST WATERS 
OVER THE NEXT COUPLE OF DAYS. THIS WILL BRING AN INCREASE IN 
NORTHERLY WINDS AND SEAS BY THIS EVENING AS PRES GRADIENT 
TIGHTENS BETWEEN THE HIGH AND LOWER PRES ACROSS SOUTHWESTERN 
UNITED STATES AND NW MEXICO. IN FACT...GALE FORCE WINDS ARE 
FORECAST TO DEVELOP JUST N OF AREA AND E OF 128W. UNDER THE 
INFLUENCE OF THIS WEATHER PATTERN...EXPECT FRESH TO STRONG 
NORTHERLY WINDS MAINLY N OF 27N BETWEEN 118W AND 130W WITH SEAS 
BUILDING TO 12 FT PRIMARILY IN NW SWELL THIS EVENING INTO WED. 
NWP GUIDANCE SUGGESTS THAT FRESH NE-E WINDS WILL BLOW ACROSS 
MOST OF THE WATERS N OF 20N W OF 120W BY WED NIGHT. ADDITIONAL 
PULSES OF NW SWELL CONTINUE TO REACH THE NW PART OF THE FORECAST 
REGION AND WILL MIX WITH NE WIND WAVES TO BUILD SEAS TO 9 FT W 
OF LINE FROM 30N116W TO 24N120W TO 20N130W TO 09N135W BY WED 
MORNING.

A STATIONARY TROUGH IS ANALYZED ON THE 1200 UTC SURFACE MAP FROM 
14N114W TO 09N115W. ISOLATED MODERATE CONVECTION IS SEEN ON 
SATELLITE IMAGERY NEAR THE TROUGH AXIS. THIS TROUGH WILL DRIFT 
WESTWARD.

WITH THE EXCEPTION OF THE GAP WIND REGIONS...MAINLY LIGHT TO 
GENTLE WINDS PREVAIL ACROSS MOST OF THE AREA E OF 110W. LONG 
PERIOD SOUTHERLY SWELL CONTINUES TO FADE ACROSS MUCH OF THIS 
REGION WITH SEAS GENERALLY 5-7 FT. ANOTHER BATCH OF CROSS 
EQUATORIAL SOUTHERLY SWELL WILL SPREAD ACROSS THE SOUTH WATERS 
TODAY AND COULD REACH THE COASTS OF CENTRAL AMERICA AND MEXICO 
BY LATE THU. 

GAP WINDS...

GULF OF TEHUANTEPEC...A HIGH RESOLUTION RAPIDSCAT FROM 1200 UTC 
PROVIDED OBSERVATIONS OF NORTHERLY WINDS IN THE 20-30 KT RANGE  
ACROSS THE GULF OF TEHUANTEPEC AND DOWNWIND TO NEAR 14N95W. THE 
WINDS ARE EXPECTED TO DROP BELOW 20 KT BY THIS EVENING. 
CLIMATOLOGICALLY...THE FINAL GALE FORCE WIND EVENT OCCURS IN THE 
GULF OF TEHUANTEPEC IN LATE MARCH OR EARLY APRIL.

GULF OF PAPAGAYO...THE SAME SCATTEROMETER PASS OBSERVED FRESH TO 
STRONG NE WINDS ACROSS THE GULF OF PAPAGAY0 AND DOWNWIND TO NEAR 
09N89W. PULSING OF NOCTURNAL WINDS ARE EXPECTED ACROSS THE GULF 
OF PAPAGAYO THROUGH THU MORNING...REACHING 20-25 KT FROM 0600 TO 
1200 UTC...WITH SEAS OF 6-7 FT THROUGH AND DOWNWIND OF THE GULF.

$$
GR

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Page last modified: Tuesday, 31-Mar-2015 15:47:40 UTC