000
AXPZ20 KNHC 161606
TWDEP 

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
1605 UTC SAT FEB 16 2013

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.

...SPECIAL FEATURE...
A DEVELOPING GALE EVENT THROUGH THE GULF OF TEHUANTEPEC 
BEGINNING IN THE NEXT FEW HOURS WILL RAPIDLY INCREASE TO STORM 
FORCE WINDS BY THIS EVENING AROUND 00 UTC...AND PERSIST THROUGH 
SUNRISE SUNDAY...BEFORE WINDS GRADUALLY DIMINISH BELOW GALE 
FORCE MONDAY MORNING.  

COOLER AND DRIER AIR IS PUSHING THROUGH THE WESTERN GULF OF 
MEXICO AND THE CHIVELA PASS IN THE ISTHMUS OF TEHUANTEPEC TOWARD 
THE GULF OF TEHUANTEPEC THIS MORNING...BEHIND A SERIES OF COLD 
FRONTAL BOUNDARIES BEING DRAGGED INTO THE GULF OF MEXICO BY A 
MAJOR UPPER LEVEL TROUGH ACROSS MOST OF THE CENTRAL AND EASTERN 
U.S. AN OVERNIGHT 0549 UTC OSCAT PASS SHOWED A SMALL PLUME OF 
NORTHERLY WINDS OF 15 TO 25 KT IN THE GULF OF TEHUANTEPEC 
EXTENDING SOUTH TO 15N...WITH AN INCREASING TREND TO GALE FORCE 
EXPECTED BETWEEN LATE MORNING AND NOON. 

A REINFORCING SURGE OF COOLER AIR BACKED BY STRONG HIGH PRES 
WILL BLAST THROUGH THE GULF OF TEHUANTEPEC BY THIS 
EVENING...ALLOWING WINDS TO INCREASE TO STORM FORCE THROUGH 
EARLY SUN MORNING. WINDS WILL START TO DIMINISH TO BELOW GALE 
FORCE LATER ON SUN AS THE DOME OF COOL AIR OVER THE GULF OF 
MEXICO MODIFIES AND SHIFTS EAST. WINDS TO 30 KT ARE STILL 
POSSIBLE MON NIGHT INTO EARLY TUE WITH DRAINAGE AFFECTS AND 
LINGER INFLUENCES OF THE COOLER AIR FILTERING INTO THE AREA. 

WW3 ENSEMBLE GUIDANCE INDICATES SEAS WILL REACH AS HIGH AS 23 FT 
WHICH IS PLAUSIBLE GIVEN STORM FORCE CONDITIONS OVER A PERIOD OF 
12 HOURS AND A FETCH OF UP TO 240 NM. A BROAD DOWNSTREAM PLUME 
OF WINDS AT LEAST 20 TO 25 KT AND SEAS 8 FT OR GREATER WILL 
SPREAD AS FAR OUT AS 600 NM SOUTHWEST OF TEHUANTEPEC.

...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH...
MONSOON TROUGH AXIS NOT DISCERNIBLE AT THIS TIME. ITCZ EXTENDS 
FROM 03N97W TO 05N104W TO 08N120W TO 03N140W. SCATTERED MODERATE 
TO STRONG CONVECTION NOTED WITHIN 90 NM OF 07.5N124W.

...DISCUSSION...
A DEEP LAYER RIDGE WILL REMAIN ANCHORED N THROUGH NW OF THE 
HAWAIIAN ISLANDS THROUGH MID WEEK...WEST OF AN ELONGATED 
MID/UPPER TROUGH EXTENDING FROM THE COAST OF NORTHERN CALIFORNIA 
TO A DEVELOPING UPPER CYCLONE CENTERED NE OF THE BIG ISLAND NEAR 
20N152W. 

FARTHER SOUTH...A NEGATIVELY TILTED UPPER TROUGH EXTENDING FROM 
15N131W TO 04N116W IS PROVIDING SUPPORT TO A SURFACE TROUGH 
BREAKING THE ITCZ NEAR 124W FROM 06N TO 11N. THE UPPER TROUGH IS 
ALSO ENHANCING CONVECTION IN THE CONVERGENT AREA AHEAD OF THE 
TROUGH NEAR 08N125W. GLOBAL MODELS SUGGEST THE SURFACE TROUGH 
WILL START TO DAMPEN OUT SUN AND MON AS IT TRANSITS W OF THE 
UPPER TROUGH WHICH WILL BE WEAKENING AND SHIFTING E.

A 1036 MB HIGH PRES AREA ASSOCIATED WITH THE DEEP LAYER RIDGE 
WILL REMAIN N OF THE AREA...CURRENTLY CENTERED NEAR 40N148W. THE 
PRES GRADIENT S OF THE HIGH PRES AND AGAINST THE SURFACE TROUGH 
ALONG THE ITCZ IS SUPPORTING A BROAD AREA OF FRESH TO STRONG 
TRADE WINDS AS NOTED IN VARIOUS SCATTEROMETER AND ALTIMETER 
PASSES OVER THE PREVIOUS 12 TO 18 HOURS IN THE GENERAL AREA FROM 
12N TO 20N W OF 125W. 

ALTIMETER DATA ALSO SHOW SEAS OF 8 TO 10 FT IN THIS AREA OF 
TRADE WINDS. THE 00Z WW3 INITIALIZATION INDICATES SEAS TO 12 FT 
FROM 06N TO 20N W OF 130W JUST TO THE WEST OF AN ALTIMETER 
PASS...AND IS PLAUSIBLE GIVEN GREATER FETCH OF NE TRADES. WW3 
AND ECWAVE GUIDANCE SUGGEST PULSES OF NW SWELL MOVING THROUGH 
THE WATERS S OF 32N OVER THE NEXT SEVERAL DAYS MIXING WITH THE 
FRESH NE SWELL IN THE TRADE WIND BELT. 

GULF OF CALIFORNIA...STRONG HIGH PRES BUILDING OVER THE GREAT 
BASIN WELL TO THE NORTH IS RESULTING IN STRONG NW 20-25 KT 
ACROSS N PORTIONS OF THE GULF...AND 15-25 KT DOWN THE REMAINDER 
OF THE LENGTH OF THE GULF OF CALIFORNIA THIS MORNING. THESE 
WINDS WILL DIMINISH LATER TODAY AS THE HIGH PRES WEAKENS.

GULF OF PAPAGAYO...THE STRONG HIGH PRES BUILDING OVER THE GULF 
OF MEXICO INTO SOUTHERN MEXICO AND CENTRAL AMERICA THAT WILL 
PROMPT STORM FORCE WINDS IN THE GULF OF TEHUANTEPEC WILL ALSO 
INDUCE A SURGE OF TRADE WINDS INTO THE GULF OF PAPAGAYO LATE SAT 
INTO EARLY SUN...PERSISTING THROUGH EARLY TUE WITH STRONGEST 
WINDS TO 30 KT DURING THE OVERNIGHT AND EARLY MORNING HOURS. 

$$
STRIPLING