000
AXPZ20 KNHC 041533
TWDEP 

TROPICAL WEATHER DISCUSSION  
NWS NATIONAL HURRICANE CENTER MIAMI FL
1605 UTC FRI JAN 04 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.

...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH...

THE MONSOON TROUGH IS ALONG 06N77W TO 07N84W. THE INTERTROPICAL 
CONVERGENCE ZONE AXIS EXTENDS FROM 07N84W TO 06N106W THEN 
RESUMES FROM 07N110W TO 06N125W TO 05N140W. SCATTERED MODERATE 
CONVECTION IS FROM 04N TO 08N E OF 80W...WITHIN 120 NM N OF THE 
ITCZ BETWEEN 122W AND 125W...AND ALSO WITHIN 90 NM N OF THE ITCZ 
BETWEEN 132W AND 136W.

...DISCUSSION...

MAINLY ZONAL WESTERLY FLOW DOMINATES THE MID AND UPPER LEVELS 
ACROSS THE DISCUSSION WATERS. AN UPPER TROUGH EXTENDS FROM NEAR 
THE FOUR CORNERS REGION OF THE U.S. TO ACROSS THE NORTHERN GULF 
OF CALIFORNIA TO 21N120W. MAINLY DRY AND STABLE AIR IS PRESENT N 
OF 20N E OF 120W. A FLATTENING UPPER RIDGE STRETCHES FROM 
32N129W TO 20N132W TO 10N131W. A 60-85 KT JET IS UNDERCUTTING 
THE RIDGE AND IS TRANSPORTING MAINLY MID LEVEL MOISTURE TO THE 
NE-E FROM THE DEEP TROPICS S OF HAWAII THROUGH A NARROW BAND TO 
ACROSS N CENTRAL MEXICO AHEAD OF THE AFOREMENTIONED UPPER TROUGH.
ANOTHER UPPER TROUGH IS SW OF CENTRAL AMERICA REACHING FROM 
10N87W THROUGH 04N83W TO COLOMBIA NEAR 03N77W. THIS UPPER 
FEATURE IS HELPING TO SUPPORT CONVECTION ALONG THE MONSOON 
TROUGH AS IS DESCRIBED ABOVE.

AT THE SURFACE...1025 MB HIGH PRES IS POSITIONED N OF THE AREA 
NEAR 37N137W WITH A BROAD RIDGE AXIS SAGGING TO THE SE TO NEAR 
20N120W. A TIGHT PRES GRADIENT SW OF THIS RIDGE AND N OF THE 
ITCZ IS AIDING THE PRESENCE OF FRESH TO STRONG TRADE WINDS 
ACROSS THE W CENTRAL WATERS. THE AREA OF STRONGEST TRADES WILL 
EXPAND BY SUN MORNING AS A COLD FRONT SNEAKS INTO THE NW WATERS. 
FRESH TO STRONG WINDS WILL ALSO INITIALLY FOLLOW THE FRONT... 
DISSIPATING BEHIND THE BOUNDARY N OF 28N AS IT WEAKENS WHILE 
PROGRESSING EASTWARD. A SET OF LONG PERIOD NW SWELL UP TO 12 FT 
IS COMMINGLING WITH NE WIND WAVES IN THE AREA OF TRADES...AS 
WELL AS MORE PURE NW SWELL OUTSIDE OF THE TRADES ALL THE WAY TO 
105W. THE SWELL WILL GRADUALLY DECAY TO LESS THAN 8 FT OVER ITS 
SE EXTENT THIS WEEKEND...WHILE A REINVIGORATING AREA OF NW SWELL 
ARRIVES BEHIND THE COLD FRONT.

A PINCHED PRES GRADIENT IS PRESENT OVER THE GULF OF CALIFORNIA 
BETWEEN SURFACE TROUGHING ALONG THE WESTERN COAST OF MEXICO AND 
THE ABOVE DISCUSSED RIDGE. FRESH TO STRONG NORTHERLY WINDS ARE 
LIKELY STILL OCCURRING IN THE FAR NORTHERN GULF WATERS N OF 
29.5N ALTHOUGH THESE SHOULD DIMINISH TO 20 KT OR LESS BY THIS 
AFTERNOON AS THE GRADIENT RELAXES.

GAP WINDS...GULF OF TEHUANTEPEC...AN OVERNIGHT OCEANSAT 
SCATTEROMETER PASS INDICATED 30-40 KT WINDS IN THE GULF OF 
TEHUANTEPEC WITH NORTHERLY FLOW BEING SUSTAINED W OF A NOW 
STALLED OUT FRONT N OF THE AREA IN THE SW GULF OF MEXICO. WINDS 
WILL CONTINUE TO PULSE TO GALE FORCE...PRIMARILY DURING THE LATE 
NIGHT AND EARLY MORNING HOURS FOR THE NEXT FEW DAYS. A 
REINFORCING NORTHERLY SURGE IS LIKELY TO ARRIVE SUN NIGHT.

GULF OF PAPAGAYO...A DEVELOPING GALE EVENT IN THE SW CARIBBEAN 
SEA WILL HELP TO INCREASE FRESH TO STRONG WINDS IN THE GULF OF 
PAPAGAYO WITH SEAS BUILDING TO UP TO 10 FT NEAR 10N90W BY SAT 
MORNING. WINDS SHOULD WEAKEN SLIGHTLY LATE SUN AS THE GALE EVENT 
ENDS IN THE CARIBBEAN.

$$
LEWITSKY