000
AXPZ20 KNHC 280920
TWDEP 

TROPICAL WEATHER DISCUSSION 
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
1005 UTC MON DEC 28 2009

TROPICAL WEATHER DISCUSSION FOR THE EASTERN PACIFIC OCEAN FROM 
THE EQUATOR TO 32N...EAST OF 140W. 

BASED ON 0600 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
0900 UTC.

...ITCZ...

THE INTERTROPICAL CONVERGENCE ZONE IS ALONG THE LINE...06N77W TO 
06N110W TO 06N140W. SCATTERED MODERATE WITH ISOLATED STRONG 
CONVECTION IS WITHIN 75 NM EITHER SIDE OF THE ITCZ FROM 130W TO 
136W.

...DISCUSSION...

MODERATE DEEP LAYER WESTERLIES ARE NORTH OF 15N. A STRONG 
SHORTWAVE IS WITHIN THESE WESTERLIES AND IS ALONG 120W NORTH OF 
15N. DEEP LAYER MOISTURE IS PRESENT EAST OF THE SHORTWAVE NORTH 
OF 23N. BROKEN TO OVERCAST MIDDLE AND UPPER LEVELS CLOUDS ARE 
NORTH OF 23N EAST OF 120W. THE SHORTWAVE IS FORECAST TO MOVE 
EAST ABOUT 30 KNOTS AND REACH BAJA CALIFORNIA LATE MONDAY. AREAS 
OF RAIN AND SOME EMBEDDED CONVECTION IS NOTED NEAR AND WITHIN 
ABOUT 200 NM EAST OF THE SHORTWAVE. THE OVERALL DEEP LAYER 
WESTERLIES ARE FORECAST TO WEAKEN THROUGH THE NEXT COUPLE OF 
DAYS.

DIFFLUENT UPPER FLOW OVER THE ITCZ WEST OF 125W IS SPREADING 
MOISTURE FROM ITCZ CONVECTION OVER THE AREA FROM ABOUT 02N TO 
12N. THE CONVECTION IS ENHANCED BY THE DIFFLUENCE ALOFT.

EXCEPT FOR THE ABOVE TWO AREAS OF MOISTURE THE AREA WEST OF 90W 
IS DRY AND CLOUD FREE IN THE MIDDLE AND UPPER LEVELS. DEEP LAYER 
MOISTURE IS PRESENT EAST OF 90W.

WEAK LOW IS NEAR 26N132W WITH A CENTRAL PRESSURE OF 1016 MB. THE 
LOW IS MOVING SOUTHEAST ABOUT 10 KT. SURFACE WINDS OF 20 KT ARE 
FORECAST WITHIN 300 NM FROM THE CENTER IN THE NORTHWEST 
SEMICIRCLE. THE LOW IS FORECAST TO WEAKEN TO A TROUGH IN 24 
HOURS. OTHERWISE A WEAK SURFACE RIDGE IS NORTH OF 12N WEST OF 
110W. WEST OF 120W THE ITCZ SURFACE PRESSURE IS LOWER DUE TO THE 
DIFFLUENCE ALOFT AND ASSOCIATED CONVECTIVE HEATING. THIS LOWER 
PRESSURE IS CAUSING THE TRADES NORTH OF THE ITCZ TO BE IN THE 20 
TO 25 KT RANGE FROM NEAR THE ITCZ TO 20N WEST OF 128W. ELSEWHERE 
A BROAD TROUGH CENTERED ON THE ITCZ IS ANALYZED AT THE SURFACE.

GAP WINDS...
GULF OF TEHUANTEPEC...N WINDS OF 20 KT ARE EXPECTED TO INCREASE 
TO 20 TO 25 KT DURING TODAY AND INCREASE TO 20 TO 30 KT AND 
SPREAD SOUTHWEST BY TONIGHT.

GULF OF PAPAGAYO...E WINDS OF 20 KT ARE EXPECTED TO INCREASE TO 
20 TO 25 KT TODAY AND INCREASE TO 20 TO 30 KT AND SPREAD EAST BY 
TONIGHT.

SEAS CONDITIONS ARE DOMINATED BY LONG PERIOD NW SWELL (WAVE 
PERIODS OF UP TO 18 SECONDS) WITH SIGNIFICANT WAVE HEIGHTS AS 
HIGH AS 16 FT PARTICULARLY OVER THE NW CORNER OF THE AREA. NOAA 
WAVE WATCH III GUIDANCE SUGGESTS THAT THIS SWELL EVENT WILL 
CONTINUE TO SPREAD SE REACHING NEAR 92W IN ABOUT 48 HOURS.

FOR ADDITIONAL INFORMATION PLEASE VISIT 
HTTP://WWW.HURRICANES.GOV/MARINE
  
$$
LL