000
AXPZ20 KNHC 180937
TWDEP 

TROPICAL WEATHER DISCUSSION 
NWS NATIONAL HURRICANE CENTER MIAMI FL
1005 UTC SAT FEB 18 2012

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 0600 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
0900 UTC.

...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH...
MONSOON TROUGH FROM 00N90W TO 06N110W TO 1011 MB LOW PRES NEAR 
05N115W TO 02N125W. ITCZ 02N125W TO BEYOND 01N140W. SCATTERED 
MODERATE WITHIN 60 NM EITHER SIDE OF TROUGH FROM 103W TO 106W. 
SIMILAR CONVECTION IS WITHIN 90 NM N OF TROUGH BETWEEN 109W AND 
113W.

...DISCUSSION...

A BROAD UPPER TROUGH EXTENDS FROM NW MEXICO TO 20N120W TO 
15N135W. AN ANTICYCLONIC CIRCULATION REMAINS CENTERED OVER 
NORTHERN CENTRAL AMERICA. IN BETWEEN THESE TWO UPPER LEVEL 
FEATURES...THERE IS A WIDE BAND OF MID TO UPPER LEVEL MOISTURE 
ROUGHLY BETWEEN 100W AND 110W. UPPER DIFFLUENCE AHEAD OF THE 
TROUGH IS ENHANCING SCATTERED MODERATE CONVECTION FROM 08N TO 
12N BETWEEN 105W AND 117W.

A 1035 MB SURFACE HIGH PRES EXTENDS A RIDGE SOUTHEASTWARD TO 
NEAR 16N105W. THIS SYSTEM IS PRODUCING FRESH TO STRONG 
NORTHEASTERLY WINDS ACROSS MUCH OF THE AREA BETWEEN THE RIDGE 
AND THE ITCZ/MONSOON TROUGH. SCATTEROMETER DATA PROVIDED 
OBSERVATIONS OF 20 TO 25 KT WINDS COVERING MAINLY THE AREA FROM 
07N TO 25N W OF 125W WHILE NE WINDS OF 20 KT WERE NOTED FROM 10N 
TO 20N BETWEEN 110W AND 125W. THIS WEATHER PATTERN IS FORECAST 
TO PERSIST OVER THE NEXT COUPLE OF DAYS AS HIGH PRES REMAINS 
NEARLY STATIONARY.  

FRESH NW TO N WINDS ARE BLOWING NEAR THE SW COAST OF MEXICO 
PARTICULARLY FROM 15N TO 20N BETWEEN 105W AND 109W. AN EARLIER 
WINDSAT PASS CONFIRMED THE PRESENCE OF THESE WINDS AS WELL AS NW 
WINDS OF 20 KT ACROSS THE SOUTHERN PORTION OF THE GULF OF 
CALIFORNIA OR SEA OF CORTEZ. THESE WINDS WILL GRADUALLY DIMINISH 
BELOW 20 KT IN ABOUT 24-36 HOURS AS PRES GRADIENT RELAXES ACROSS 
THE AREA.

AS A NEW UPPER TROUGH DROPS S ALONG THE CALIFORNIA COAST EARLY 
ON SUN...THE REMNANTS OF ITS ASSOCIATED SURFACE COLD FRONT WILL 
MOVE INTO NW WATERS BRINGING FRESH NW TO N WINDS AND NW SWELL TO 
14 FEET. 

...GAP WINDS...

NE TO E WINDS AT 20 KT WILL CONTINUE TO PULSE THROUGH THE GULF 
OF PAPAGAYO OVER THE NEXT COUPLE OF DAYS. STRONGEST WINDS OCCUR 
DURING EARLY MORNING HOURS WITH THE AID OF DRAINAGE FLOW. 

EXPECT INCREASING WINDS AND SEAS ACROSS THE GULF OF TEHUANTEPEC 
BY SUN AFTERNOON. A BRIEF EPISODE OF WINDS REACHING GALE FORCE 
IS EXPECTED BY SUN EVENING. BOTH...THE GFS GLOBAL MODEL AND THE 
NAM REGIONAL MODEL SUGGEST WINDS OF 35 KT BEGINNING AT 20/0000 
UTC. A GALE WARNING HAS BEEN ISSUED FOR THAT AREA. THIS GAP WIND 
EVENT WILL BE ASSOCIATED WITH A COLD FRONT MOVING SE ACROSS THE 
GULF OF MEXICO. WHEN COLD AIR OUTBREAKS OCCUR OVER THE GULF OF 
MEXICO...THE SIERRA MADRE MOUNTAINS BLOCK THE LARGE SCALE FLOW 
OF COLD AIR SOUTHWARD RESULTING IN THE DEVELOPMENT OF STRONG 
NORTH-SOUTH PRES GRADIENT ACROSS THE ISTHMUS OF TEHUANTEPEC. NLY 
FLOW IS THEN FUNNELED THROUGH THE CHIVELA PASS INTO THE GULF OF 
TEHUANTEPEC. THIS GAP FLOW OFTEN RESULTS IN A NARROW JET OF 
WINDS THAT CAN REACH GALE...STORM AND OCCASIONALLY HURRICANE 
FORCE. 
 
$$
GR