000
AXPZ20 KNHC 151558
TWDEP 

TROPICAL WEATHER DISCUSSION  
NWS NATIONAL HURRICANE CENTER MIAMI FL
1605 UTC SAT DEC 15 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 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
1430 UTC.

...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH...
THE MONSOON TROUGH EXTENDS FROM COASTAL COLOMBIA NEAR 09N76W TO 
09.5N84W TO 06N104W...WHERE IT TRANSITIONS TO ITCZ...CONTINUING 
ON TO 06.5N107W TO 08N132W TO BEYOND 08N140W. SCATTERED MODERATE 
CONVECTION NOTED S OF TROUGH TO 04.5N BETWEEN 78W AND 86W. 
ISOLATED CLUSTER OF MODERATE TO STRONG CONVECTION WITHIN 120 NM 
OF 07.5N108W. SCATTERED TO LOCALLY NUMEROUS MODERATE TO STRONG 
CONVECTION NOTED FROM 07N TO 14N W OF 127W.  

...DISCUSSION...

AT UPPER LEVELS...AN ELONGATED MIDDLE TO UPPER TROUGH EXTENDS 
FROM THE NW U.S. THROUGH 30N120W TO 18.5N139W...THEN CONTINUES 
W-NW AS A NARROW TUTT ACROSS THE HAWAIIAN ISLANDS. A SHORTWAVE 
TROUGH DIVING SE THROUGH BACKSIDE OF TROUGH...FROM 31N120W TO 
26N127W...WAS BEGINNING TO SETTLE INTO MEAN TROUGH AXIS E OF 
130W...WHILE AN ASSOCIATED SMALL MIDDLE LEVEL VORTEX NEAR 
31N121W WAS SUPPORTING A 1010 MB SURFACE LOW CENTERED N OF THE 
AREA NEAR 32N117.5W. THE LOW WAS DRAGGING A COLD FRONT INTO THE 
REGION...EXTENDING FROM 31N116.5W TO 27N120W TO 28N132W. 
OVERNIGHT ASCAT PASSES FROM 0500 TO 0600 UTC SHOWED WINDS 20-30 
KT WITHIN 240 NM ACROSS THE W SEMICIRCLE OF THIS LOW...OCCURRING 
MAINLY N OF 30N AND THE LOCAL WATERS... WITH NW TO W WINDS 20-25 
KT SPREADING DIRECTLY BEHIND THE COLD FRONT AND ACROSS THE LOCAL 
WATERS. SEAS WITHIN THIS ZONE OF STRONG WINDS HAVE BUILT TO 9-12 
FT THIS MORNING. THIS LOW AND SUPPORTING SHORTWAVE WILL SHIFT 
EWD AND INLAND DURING THE NEXT 24 HOURS...AND MOVE ACROSS 
PORTIONS OF BAJA CALIFORNIA NORTE...AND INTO NW PORTIONS OF 
MEXICO AND ARIZONA. A VERY STRONG AND BROAD UPPER LEVEL RIDGE 
WAS CENTERED ACROSS THE N CENTRAL PACIFIC ALONG 34N AND WAS 
BUILDING SE...HELPING TO FORCE THE MEAN UPPER TROUGH SLIGHTLY 
SE...AND FURTHER ELONGATE IT. S OF THE UPPER TROUGH A STRONG 
SUBTROPICAL JET PREVAILED...FROM 15N142W TO A BROAD JET OF 
85-110 KT MOVING ACROSS BAJA CALIFORNIA SUR AND ACROSS NW 
MEXICO. THIS JET WAS TRANSPORTING ABUNDANT UPPER MOISTURE IN THE 
FORM OF A 600 NM WIDE ZONE OF BROKEN TO OVERCAST HIGH CLOUDS 
FROM 125W...NE ACROSS N MEXICO AND INTO THE CENTRAL U.S.

A 1031 MB SURFACE HIGH WAS CENTERED ACROSS THE N CENTRAL PACIFIC 
NEAR 32N152W...WITH A BROAD RIDGE EXTENDING SE...AND AHEAD OF 
THE AFOREMENTIONED COLD FRONT TO NEAR 22N110W. THE INDUCED 
PRESSURE GRADIENT BETWEEN THE ITCZ AND THE HIGH HAVE CREATED A 
BROAD ZONE OF STRONG NE TO E TRADES S OF 22N-24N AND W OF 125W 
CONTINUING BEYOND 140W AND INTO THE CENTRAL PACIFIC. SEAS OF 
8-10 FT PREVAILED WITHIN THIS ZONE E OF 140W THIS MORNING...WITH 
EARLY MORNING ALTIMETER PASSES INDICATING SMALL ISOLATED AREAS 
TO 11 FT. LOW LEVEL CONVERGENCE OCCURRING WITHIN THIS BROAD ZONE 
OF NE TO E TRADEWINDS CONTINUES TO INDUCE SCATTERED TO LOCALLY 
NUMEROUS CONVECTION FROM 07N TO 14N W OF 127W. DIVERGENCE ALOFT 
ASSOCIATED WITH THE UPPER JET IS ACTING TO ENHANCE AND SUSTAIN 
MUCH OF THIS ACTIVITY. MOIST AND UNSTABLE CONDITIONS WILL 
PREVAIL ACROSS THIS REGION OVER THE WEEKEND AND INTERACT WITH 
THE JET TO MAINTAIN ACTIVE CONVECTION THERE. 

THE PRESSURE GRADIENT BETWEEN THE SURFACE RIDGE AND TROUGHING 
OVER CENTRAL MEXICO IS ALSO MAINTAINING FRESH NORTHERLY WINDS 
OFF THE COAST OF MEXICO FROM 18N TO 20N E OF 107W...WHERE SEAS 
ARE 6-8 FT. A STRONG SURFACE RIDGE IS EXPECTED TO PERSIST OVER 
THE N PART OF THE AREA OVER THE NEXT COUPLE OF DAYS...WHILE 
SHIFTING VERY SLOWLY EWD...WHICH WILL MAINTAIN THE AREA OF FRESH 
TO STRONG TRADEWINDS N OF THE ITCZ THROUGH THE WEEKEND. BY 
MONDAY MORNING...THE SURFACE HIGH IS EXPECTED TO HAVE SHIFTED 
FAR ENOUGH EASTWARD TO INDUCE FRESH NLY WINDS AROUND 20 KT 
ACROSS THE S HALF OF THE GULF OF CALIFORNIA...AND EXTEND SWD TO 
NEAR 18N.  

GAP WINDS
GULF OF TEHUANTEPEC...N WINDS HAVE DIMINISHED TO 20-25 KT 
OVERNIGHT AND THROUGH THE MORNING HOURS...AND ARE EXPECTED TO 
WEAKEN TO LESS THAN 20 KT LATE THIS MORNING...BECOMING LIGHT AND 
VARIABLE BY EVENING. LOOKING AHEAD...ANOTHER STRONG NLY GAP 
WINDS EVENT WILL BE POSSIBLE LATE NEXT WEEK WITH THE POTENTIAL 
FOR STORM CONDITIONS BY FRI. MODERATE TO FRESH NE TRADEWINDS 
ACROSS THE W AND NW CARIBBEAN ARE PRODUCING MODERATE NE GAP 
WINDS ALONG THE TYPICAL PACIFIC COASTAL ZONES OF CENTRAL 
AMERICA. LOOK FOR THESE WINDS TO PULSE TO 20-25 KT DURING THE 
EARLY MORNING HOURS SUNDAY...PARTICULARLY THROUGH THE GULF OF 
PAPAGAYO...BEFORE WEAKENING SUNDAY NIGHT THROUGH MONDAY AS 
TRADEWINDS BECOME EASTERLY ACROSS THE W CARIBBEAN.

$$
STRIPLING