000
AXPZ20 KNHC 201002
TWDEP 

TROPICAL WEATHER DISCUSSION  
NWS NATIONAL HURRICANE CENTER MIAMI FL
1005 UTC THU JAN 20 2011

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 
0945 UTC.

...ITCZ...

THE INTERTROPICAL CONVERGENCE ZONE AXIS IS CENTERED ALONG 6N78W
5N94W 5N105W 6N117W 6N126W 7N140W. SCATTERED MODERATE CONVECTION 
IS WITHIN 120 NM S OF THE AXIS BETWEEN 87W-91W AND 120 NM N OF 
THE AXIS W OF 138W.

...DISCUSSION...

AN UPPER LEVEL TROUGH EXTENDING FROM THE SOUTHWESTERN U.S. TO
CENTRAL BAJA CALIFORNIA AND TO 26N121W AND W TO 26N131W WILL
SHIFT E OF THE AREA TONIGHT AND FRI. SATELLITE WATER VAPOR 
IMAGERY SHOWS MODERATE SUBSIDENCE AND RESULTANT DRY AIR N OF THE 
TROUGH AS WELL AS S OF THE TROUGH TO 20N. A JET STREAM BRANCH 
DIVES SE INTO THE AREA THROUGH 32N139W TO 26N131W...THEN ROUNDS 
THE BASE OF THE TROUGH TO EXTENDING ENE TO OVER SOUTHERN BAJA
CALIFORNIA...AND TO ACROSS NORTHERN MEXICO. SCATTERED THIN 
HIGH CIRRUS CLOUDS ARE VISIBLE WITHIN 180 NM S OF THIS JET
W OF 134W...AND BETWEEN 120W-130W. WEAKER UPPER LEVEL RIDGING
THAT WAS PRESENT OVER MUCH OF THE WESTERN AND CENTRAL SECTIONS
OF THE REGION DURING THE PAST FEW DAYS HAS SHIFTED TO JUST W 
OF 140W AND N OF 22N. AN ASSOCIATED NARROWING RIDGE STRETCHES
FROM THE RIDGE NEWD TO AN ANTICYCLONE WELL N OF THE AREA NEAR 
36N132W. BROAD ANTICYCLONIC FLOW EXISTS AROUND THE ANTICYCLONE
...WITH UPPER LEVEL MOISTURE SPILLING SWD AROUND THE ANTICYCLONIC
FLOW AND APPROACHING NEAR 32N OVER THE NE PORTION OF THE AREA 
BEFORE IT ERODES IN THE SUBSIDENCE AREA. 

THE SOUTHERN STREAM OF THE ABOVE UPPER TROUGH...DERIVED FROM A
LARGE UPPER LEVEL LOW S OF THE HAWAIIAN ISLANDS DRIFTING 
SW...CROSSES 140W AT 14N AND EXTENDS ENE TO 16N120W...NE TO 
21N110W AND CONTINUES NEWD ACROSS NE MEXICO. SCATTERED TO
BROKEN HIGH CIRRUS CLOUDS ARE NOTED S OF THE THIS STREAM AND
W OF 128W. SLIGHTLY DIFFLUENT FLOW FROM 9N TO 13N W OF 137W
IS SUPPORTING ITCZ CONVECTING IN THAT AREA. EARLIER DEEP 
ATMOSPHERIC MOISTURE SEEN OVER THE REMAINDER OF THE TROPICAL
BELT W OF 120W HAS DIMINISHED OVER THE PAST 24 HOURS AS THE UPPER
LEVEL LOW W OF THE AREA PULLS FURTHER TO THE SW. 

WITHIN THE SOUTHERN STREAM...A MID LEVEL TROUGH EXTENDS FROM 
15N124W SE TO 11N118W TO NEAR 5N108W. THE TROUGH WILL SHIFT EWD 
TO CLOSE TO MEXICO BY SAT NIGHT AS THE UPPER LOW W OF THE AREA 
SHEARS OUT INTO A TROUGH THAT THEN BEGINS TO SLIDE EWD. IN 
RESPONSE TO THIS...A LARGE MID/UPPER RIDGE WILL DEVELOP AHEAD OF 
IT S OF 18N AND TO W OF THE TROUGH NEAR MEXICO FRI AND SAT WHILE 
A PIECE OF ENERGY IN THE FORM OF AN UPPER LEVEL LOW BREAKS OFF 
THE UPPER TROUGH DESCRIBED IN FIRST PARAGRAPH. THIS FEATURE THEN 
MOVES TO THE FAR WESTERN SECTION OF THE AS IT IS NUDGED WWD BY 
STRONG MID/UPPER LEVEL RIDGING THAT PREVAILS TO ITS N. THIS LOW 
WILL THEN RE-ESTABLISHED THE SOUTHERN STREAM WITH ADDITIONAL 
UPPER ENERGY CHANNELED THROUGH THE AREA LEADING TO INCREASING 
DEEP MOISTURE OVER MAINLY THE WESTERN PORTION. 

TO THE S AND SE OF THE MID LEVEL TROUGH...MODERATE SUBSIDENCE
COVERS THE AREA AND IS SUPPRESSING ANY DEEP CONVECTION FROM 
DEVELOPING WITH ONLY ISOLATED SMALL CLUSTERS OF WEAK CONVECTION 
OCCURRING E OF 84W TO NEAR THE COLOMBIAN COAST AS BROAD MID/UPPER
LEVEL RIDGING STRETCHES NWWD FROM AN ANTICYCLONE ANCHORED OVER 
NW VENEZUELA TO SE MEXICO. MODERATE TO STRONG UPPER LEVEL WINDS
S OF THE RIDGING IS TRANSPORTING EXTENSIVE UPPER LEVEL MOISTURE 
FROM S AMERICA WWD INTO THE FAR EASTERN PORTION OF THE AREA S OF 
9N AND E OF 91W.

AT THE SURFACE...A STRONG HIGH CENTER IS LOCATED WELL TO THE
N OF THE AREA WITH A RIDGING EXTENDING SEWD TO 32N132W AND TO 
22N122W. A TIGHT PRES GRADIENT ON THE SOUTHERN PERIPHERY OF THE 
RIDGE DUE TO THE PRES DIFFERENCE BETWEEN IT AND COMPARATIVELY 
LOWER PRESSURES TO ITS S IS RESULTING IN NE TO E 20 KT TRADE 
WINDS OVER THE AREA BOUNDED FROM 10N TO 20N W OF 126W. THESE 
TRADES ARE FORECAST TO SLIGHTLY SHRINK IN AREAL COVERAGE OVER 
THE NEXT 24 TO 48 HOURS AS THE HIGH CENTER SHIFTS SOME TO THE 
SW. A TIGHT PRES GRADIENT OVER THE FAR NE PORTION OF THE AREA 
DUE TO THE PRES DIFFERENCE BETWEEN THE RIDGE AND THE CALIFORNIA 
COASTAL TROUGH IS ALLOWING FOR N TO NE WINDS OF 20 TO 25 KT TO 
EXIST N OF 25N BETWEEN 120W AND 133W...WITH WINDS TO MINIMAL 
GALE FORCE JUST N OF 32N. THESE WINDS ARE FORECAST TO DIMINISH 
TO 20 KT IN 24 HOURS AND CONTINUE THROUGH 48 HOURS AS THE 
GRADIENT SLACKENS SOME. SEAS OF 10 TO 14 FT IN MIXED NW AND N 
SWELL SUBSIDE TO 8 TO 10 FT IN 24 HOURS.

ELSEWHERE AT THE SURFACE...WEAK TROUGH MOVING WWD ARE ALONG 
87W...104W AND 122W FROM 3N TO 8N MOVING W ABOUT 10 KT...AND
VOID OF CONVECTION.

WITH RESPECT TO OTHER MARINE ISSUES...LARGE LONG PERIOD NW 
SWELLS WITH PERIODS OF 13-15 SEC ARE RESULTING IN SEAS OF 8 TO 
11 FT ELSEWHERE N OF 20N AND W OF 115W. THESE SWELLS...GENERATED 
FROM A SERIES OF INTENSE LOW PRES SYSTEMS WELL NW OF THE REGION 
ARE FORECAST BY WAVEWATCH GUIDANCE TO BUILD UP 15 FT BY 48 
HOURS.

GAP WINDS...
NEXT GULF OF TEHUANTEPEC EVENT IS FORECAST TO BEGIN ON FRI 
AFTERNOON AS HIGH PRES BUILDS S ACROSS MEXICO AND WESTERN GULF 
OF MEXICO IN THE WAKE OF A COLD FRONT THAT MOVES THROUGH THE BAY 
OF CAMPECHE AND SOUTHEASTERN MEXICO. PRESENT INDICATIONS ARE 
THAT N WINDS THROUGH THE ISTHMUS OF TEHUANTEPEC ARE EXPECTED IN 
THE RANGE OF 20 TO 30 KT...THEN REDUCE SLIGHTLY BY 48 HOURS.

NW WINDS ARE EXPECTED TO INCREASE TO 20 TO 25 KT OVER THE FAR 
NORTHERN WATERS OF THE GULF OF CALIFORNIA THIS AFTERNOON AS 
BROAD AND STRONG HIGH PRES SETTLES IN OVER THE INTERMOUNTAIN 
REGION OF THE U.S. AND INTERACTS WITH SURFACE TROUGHINESS OVER 
NW MEXICO AND THE NORTHERN GULF OF CALIFORNIA ALLOWING FOR THE 
CULPRIT STEEP PRES GRADIENT TO BECOME PRESENT. THESE WINDS ARE
FORECAST TO WEAKEN TO 20 KT BY 48 HOURS FROM 26N TO 29N.

$$
AGUIRRE