000
AXPZ20 KNHC 081003
TWDEP 

TROPICAL WEATHER DISCUSSION  
NWS NATIONAL HURRICANE CENTER MIAMI FL
1005 UTC SUN JAN 08 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 AXIS EXTENDS FROM 08N76W TO 05N80W TO 07N85W TO 
03.5N95W...WHERE IT TRANSITIONS TO ITCZ...CONTINUING ON TO 
05N106W TO 08.5N127W TO BEYOND 06N140W. ISOLATED TO SCATTERED 
MODERATE TO STRONG CONVECTION NOTED S OF AXIS E OF 86W. 
SCATTERED MODERATE TO STRONG CONVECTION NOTED WITHIN 270 NM N OF 
AXIS W OF 128W. SCATTERED MODERATE ISOLATED STRONG CONVECTION 
WAS OCCURRING WELL REMOVED FROM THE ITCZ...FROM 12.5N TO 19N W 
OF 135W.

...DISCUSSION...

A NARROW MIDDLE TO UPPER LEVEL TROUGH MEANDERS ACROSS FAR NW 
PORTIONS OF THE AREA...EXTENDING INTO A LINGERING AND QUASI 
STATIONARY UPPER TROUGH JUST W OF THE AREA...WITH MIDDLE LEVEL 
CYCLONE NOTED NEAR 20N143W...AND TROUGH EXTENDING S-SW TO NEAR 
06N150W. BROAD UPPER RIDGING E OF THIS TROUGH HAS BUILT N DURING 
THE PAST 12 HOURS IN RESPONSE TO THE TROUGH BECOMING MORE N-S 
ALIGNED AND CROSS EQUATORIAL RIDGING ALONG 130W...AND CONTINUES 
TO PERTURB THE ITCZ INVOF 130W. ACTIVE CONVECTION NOTED ABOVE IS 
OCCURRING UNDERNEATH THIS RIDGE...ENHANCED BY DIFFLUENT FLOW IN 
THE SE QUADRANT OF THE UPPER TROUGH TO THE W...WHICH IN TURN HAS 
INDUCED STRONG DIVERGENCE ALOFT. THIS TROUGH WILL SHIFT VERY 
SLOWLY E OVER THE NEXT COUPLE DAYS...WITH ACTIVE CONVECTION 
EXPECTED TO CONTINUE BETWEEN 128W AND 140W WITHIN A FEW DEGREES 
N OF THE ITCZ.

A 1030 MB HIGH PRES CENTER WAS LOCATED N OF THE AREA NEAR 
39N130W WITH RIDGE EXTENDING SE TO NEAR 22N114W. THE PRESSURE 
GRADIENT BETWEEN THE AREA OF HIGH PRESSURE AND LOWER PRESSURE IN 
THE VICINITY OF THE ITCZ IS MAINTAINING FRESH TRADEWINDS FROM 
08N TO 16N W OF 128W...WHICH ARE PROVIDING THE LOW LEVEL FORCING 
FOR THE CONVECTION MENTIONED ABOVE. LONG PERIOD NW SWELL WITH 
PERIODS OF 17-19 SECONDS ALONG THE LEADING EDGE OF THE SWELL 
TRAIN CONTINUES TO MOVE SE THROUGH THE FORECAST WATERS...WITH 
COMBINED SEAS 8 TO 10 FT CURRENTLY COVERING MUCH OF THE AREA W 
OF 110W. THESE SWELLS WILL CONTINUE TO PROPAGATE SE...REACHING 
THE GALAPAGOS ISLANDS ALONG 91W BY MON AFTERNOON...THEN THE NW 
COAST OF S AMERICA MON NIGHT...WHILE SLOWLY SUBSIDING. 

THE PRESSURE GRADIENT BETWEEN THE HIGH PRESSURE CENTER MENTIONED 
ABOVE AND TROUGHING ACROSS CALIFORNIA IS PRODUCING FRESH 
NORTHERLY WINDS N OF 29N BETWEEN 120W AND 126W. WINDS WILL 
DIMINISH BELOW 20 KT BY EARLY SUN AS THE AREA OF HIGH PRESSURE 
WEAKENS. 

GULF OF PAPAGAYO...FRESH TRADE WINDS OVER THE WESTERN CARIBBEAN 
ARE FLOWING THROUGH THE GAPS IN THE TOPOGRAPHY OVER NICARAGUA 
AND COSTA RICA INTO THE GULF OF PAPAGAYO. WINDS WILL PEAK AT 20 
TO 25 KT DURING THE EARLY MORNING HOURS WITH THE ADDED COMPONENT 
OF NOCTURNALLY DRIVEN KATABATIC WINDS AND THEN REDUCE TO AROUND 
20 KT THROUGHOUT THE DAY AND EARLY EVENING HOURS. LITTLE CHANGE 
IN THIS PATTERN IS EXPECTED THROUGH MON. AS THE AREA OF HIGH 
PRESSURE OVER THE SW N ATLC WATERS WEAKENS EARLY NEXT WEEK... 
WINDS OVER THE CARIBBEAN WATERS WILL DIMINISH. THIS WILL 
DIMINISH WINDS FUNNELING ACROSS THE GULF OF PAPAGAYO...WITH 
WINDS EXPECTED TO FINALLY DIMINISH BELOW 20 KT TUE.

HIGH PRESSURE BUILDING ACROSS THE GREAT BASIN REGION EARLY THIS 
MORNING HAS BEGUN TO TIGHTEN THE PRES GRADIENT ACROSS THE 
NORTHERN GULF OF CALIFORNIA. AS THE HIGH SHIFTS S AND SE TODAY 
AND TONIGHT...NWLY WINDS WILL INCREASE TO 20 TO 30 KT THROUGH 
THE N HALF OF THE GULF OF CALIFORNIA THIS MORNING...AND SPREAD S 
THROUGH THE ENTIRE LENGTH OF THE GULF BY MONDAY MORNING. SEAS 
ARE EXPECTED TO BUILT TO AROUND 8 FT BY THIS AFTERNOON. 

$$
STRIPLING