000
AXPZ20 KNHC 211612
TWDEP 

TROPICAL WEATHER DISCUSSION    
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
1605 UTC SAT APR 21 2007

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 
1545 UTC.

...ITCZ...

ITCZ AXIS IS CENTERED ALONG 9N86W 7N100W 6N112W 6N120W 4N130W
3N140W. SCATTERED STRONG CONVECTION IS WITHIN 90 NM S OF THE
AXIS BETWEEN 112W-116W...AND 60 NM S OF THE AXIS BETWEEN 
129W-132W. SCATTERED MODERATE/ISOLATED STRONG CONVECTION IS
WITHIN 75 NM EITHER SIDE OF THE AXIS BETWEEN 120W-122W...60 NM
EITHER SIDE OF THE AXIS BETWEEN 124W-126W...AND ALSO WITHIN
30 NM OF THE AXIS BETWEEN 116W-120W. SCATTERED MODERATE 
CONVECTION EXISTS FROM 5N-9N E OF 87W.

...DISCUSSION...

A MID/UPPER LEVEL CYCLONIC CIRCULATION OVER THE SW UNITED STATES
HAS A TROUGH EXTENDING SW TO CENTRAL BAJA CALIFORNIA...
AND IS RAPIDLY MOVING E OF THE AREA. STRONG NW FLOW FOLLOWS
IN THE WAKE OF THE TROUGH W OF 122W. ANOTHER MID/UPPER LEVEL
CYCLONIC CIRCULATION IS NOTED ON WATER VAPOR IMAGERY TO BE 
LOCATED NEAR 22N128W MOVING E ABOUT 20 KT. IT IS EMBEDDED IN 
A LARGE ENVELOPE OF CYCLONIC FLOW THAT GENERALLY COVERS THE 
AREA FROM 20N-26N W OF 128W. A TROUGH EXTENDS WNW FROM THE 
CYCLONIC CIRCULATION TO W OF THE DISCUSSION AREA AT 23N140W.
MID/UPPER LEVEL RIDGING EXTENDS ESE INTO THE AREA N OF 26N
W OF 127W. WATER VAPOR IMAGERY SHOWS MODERATE SUBSIDENCE AND
ASSOCIATED DRY AIR FROM 16N-24N W OF 128W. A SUBTROPICAL JET 
STREAM BRANCH EXTENDS INTO THE REGION THROUGH 16N140W AND 
CONTINUES ENE THROUGH 18130W 24N122W AND SE TO ACROSS THE
SRN TIP OF BAJA CALIFORNIA AND NEW ACROSS NW MEXICO. MAXIMUM 
JET CORE WINDS AS INDICATED BY SATELLITE-DERIVED WINDS ARE IN 
THE 70-95 KT RANGE IN THE AREA JUST TO THE E THROUGH S OF THE 
CYCLONIC CIRCULATION. BROAD MID/UPPER LEVEL RIDGING DOMINATES
THE SRN PORTION TO THE S OF THE JET STREAM AND W OF 110W.
UPPER LEVEL MOISTURE SEEN AS BROKEN MOSTLY HIGH CLOUDS ARE 
STREAMING NEWD WITHIN 330 NM SE OF THE JET BETWEEN 119W-127W
...AND ELSEWHERE WITHIN 120 NM S OF THE JET.

OVER THE ERN SECTION...THE FLOW BECOMES DIFFLUENT E OF 112W. 
ITCZ CONVECTION BETWEEN 109W-135W HAS INCREASED SIGNIFICANTLY 
SINCE 24 HRS...AND IS THE MOST ACTIVE OBSERVED SO FAR THIS 
SPRING.  BROAD MID/UPPER LEVEL RIDGING E OF THE DIFFLUENT FLOW 
PATTERN COVERS THE NRN PART OF S AMERICA AND MUCH OF THE WRN 
CARIBBEAN AND CENTRAL AMERICAN LAND BASIN. THE FLOW BETWEEN BOTH 
THE RIDGE AND THE DIFFLUENCE IS SPREADING HIGH LEVEL DEBRIS 
CLOUDINESS NWD TOWARDS CENTRAL AMERICA. A WEAK BROAD MID LEVEL
CYCLONIC CIRCULATION MOVING W 10 KT IS OBSERVED ON BOTH VISIBLE
IR IMAGERY TO ALONG THE ITCZ BETWEEN 88W-90W FROM 4N-8N...BUT
IS VOID OF ANY DEEP CONVECTION FOR TIME BEING.

AT THE SFC...A STATIONARY 1025 MB HIGH CENTER IS ANALYZED NW OF 
THE DISCUSSION AREA NEAR 30N147W WITH A RIDGE EXTENDING ESE 
THROUGH 28N138W 26N126W TO 23N118W. HIGH PRES COVERS THE AREA N 
OF 16N W OF 118W. THE PRES GRADIENT RESULTING FROM THE RIDGE IS 
RESULTING IN NE TRADES OF 20 KT FROM 6N-23N W OF 125W. NW WINDS 
OF 20 KT WERE NOTED ON A QUIKSCAT PASS FROM AROUND 1330 UTC TO 
BE CONFINED OVER THE NE PART FROM 21N-25N E OF 118W TO THE COAST 
OF BAJA CALIFORNIA. THESE WINDS ARE EXPECTED TO DIMINISH IN 
ABOUT 36 HRS AS THE HIGH SLOWLY MOVES E AND WEAKENS.

$$
AGUIRRE