000
AXPZ20 KNHC 200932
TWDEP 

TROPICAL WEATHER DISCUSSION     
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
1005 UTC FRI MAR 20 2009

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

BASED ON 0000 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
0230 UTC.

...ITCZ...
THE ITCZ AXIS LIES ALONG A LINE FROM 08N84W TO 03N100W TO 
05N115W TO 04N130W TO 03N140W. NO DEEP CONVECTION IS NOTED ALONG 
THE ITCZ.

...DISCUSSION...

A DEEP LAYERED TROUGH CURRENTLY MOVING EWD N OF THE AREA WILL 
CLIP THE NORTHERN FORECAST WATERS SAT INTO SUN. AT THE SAME 
TIME...A CUT-OFF LOW WILL FORM OVER THE NW PORTION OF THE AREA 
ON SUN. THE UPPER TROUGH SUPPORTS A COLD FRONT FORECAST TO ENTER 
THE NORTHERN WATERS BY SUNDAY. NW TO N WINDS OF 20 TO 30 KT AND 
WAVE HEIGHTS OVER 14 FT IN NORTHWESTERLY SWELL WILL FOLLOW THE 
FRONT. STRONG HIGH PRES IN THE WAKE OF THE FRONT WILL BRING AN 
INCREASE IN WINDS AND SEAS ACROSS THE FORECAST AREA LATE SUN 
PARTICULARLY JUST WEST OF THE BAJA PENINSULA. THE TRADES ARE 
ALSO EXPECTED TO PICK UP SUBSTANTIALLY ON SUNDAY AS THE SURFACE 
HIGH BUILDS SOUTHWARD. IN ADDITION...LONG PERIOD SW SWELL ARE 
FORECAST BY WWIII TO AFFECT THE PACIFIC COAST OF MEXICO...EAST 
OF MANZANILLO...AND CENTRAL AMERICA ON SUNDAY.  

IN THE MEANTIME...A SFC RIDGE DOMINATES THE REGION N OF 15N AND 
WEST OF 110W. THIS FEATURE WILL DISSIPATE DURING THE NEXT DAY IN 
RESPONSE TO THE AMPLIFICATION OF THE ABOVE MENTIONED UPPER-LEVEL 
TROUGH. UNDER THE INFLUENCE OF THIS SYSTEM...TRADE WINDS OF 20 
KT AND SEAS TO 9 FT IN MIXED NW AND NE SWELL ARE PRESENT. 

FARTHER TO THE E...DEEP LAYERED DRY AIR AND STABLE ATMOSPHERIC 
CONDITIONS EMBEDDED WITHIN AN UPPER RIDGE ARE RESULTING IN FAIR 
WEATHER CONDITIONS S OF 16N E OF 100W. ONLY ISOLATED TSTMS ARE 
NOTED NEAR 5N86W.

GAP WINDS...
A PERSISTENT RIDGE OF SURFACE HIGH PRESSURE OVER MEXICO AND THE 
GULF OF MEXICO WILL SUPPORT A RELATIVELY STRONG SURFACE PRESSURE 
GRADIENT ACROSS THE ISTHMUS OF TEHUANTEPEC DURING THE NEXT FEW 
DAYS. STRONG HIGH PRES BUILDING SWD ACROSS THE EASTERN CONUS AND 
THE GULF OF MEXICO WILL STEEPEN THE PRESSURE GRADIENT ACROSS THE 
ISTHMUS OF TEHUANTEPEC EVEN FURTHER ON SATURDAY. IN FACT...GALE 
FORCE WINDS ARE EXPECTED FROM LATE TONIGHT THROUGH SATURDAY 
MORNING IN THE GULF OF TEHUANTEPEC...GIVEN THE STRONG PRESSURE 
GRADIENT SW OF A 1035 MB SURFACE HIGH OVER THE MID ATLANTIC 
STATES THIS WEEKEND. SEAS IN THE 8 TO 9 FT RANGE ARE EXPECTED. 
ALSO...WINDS OF UP TO 20 KT ARE BLOWING IN THE GULF OF PAPAGAYO. 
THIS WEATHER PATTERN IS FORECAST TO PERSIST WITHIN THE NEXT 48 
HOURS AS THE RIDGE OF HIGH PRES STRENGTHENS OVER THE W ATLC AND 
CARIBBEAN.  

$$
GR