Tropical Depression SEVENTEEN-E

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TROPICAL DEPRESSION SEVENTEEN-E DISCUSSION NUMBER   1
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   EP172006
200 AM PDT SAT OCT 21 2006
 
CONVENTIONAL AND MICROWAVE SATELLITE IMAGERY...ALONG WITH NEARBY
SHIP REPORTS...INDICATE THE TROPICAL DISTURBANCE CENTERED ABOUT 230
NMI SOUTH-SOUTHWEST OF MANZANILLO MEXICO HAS ORGANIZED INTO
TROPICAL DEPRESSION SEVENTEEN-E. THE INITIAL INTENSITY OF 30 KT IS
BASED ON SATELLITE INTENSITY ESTIMATES OF T2.0/30 KT FROM BOTH TAFB
AND SAB. IN ADDITION...AT 21/0600Z SHIP A8HR7 IN THE NORTHEASTERN
QUADRANT REPORTED 27 KT WINDS...WHILE SHIP SFMN LOCATED ABOUT 45
NMI SOUTH OF THE CENTER REPORTED A WEST WIND OF 25 KT.

THE INITIAL MOTION ESTIMATE IS 270/10 KT. TD-17E IS EXPECTED TO MOVE
WESTWARD ACCOMPANIED BY A GRADUAL DECREASE IN FORWARD SPEED FOR THE
NEXT 36-48 HOURS AS THE CYCLONE NEARS THE SOUTHWESTERN PERIPHERY OF
A NARROW SUBTROPICAL RIDGE. A MASSIVE MID- TO UPPER-LEVEL
LOW/TROUGH LOCATED OFF THE COASTS OF CALIFORNIA AND BAJA CALIFORNIA
IS FORECAST TO SLOWLY MOVE EASTWARD AND ERODE THE WESTERN PORTION
OF THE SUBTROPICAL RIDGE BY 48-72 HOURS...ALLOWING THE TROPICAL
CYCLONE TO TURN NORTHWARD AND EVENTUALLY RECURVE TO THE NORTHEAST
BY 96 HOURS. A 120-HOUR POSITION WAS INCLUDED FOR CONTINUITY
PURPOSES DUE TO POSSIBLE LANDFALL ALONG THE SOUTHWESTERN COAST OF
MEXICO BETWEEN 96 AND 120 HOURS. HOWEVER...THIS POSITION IS AN
ESTIMATE OF THE MID- TO UPPER-LEVEL CIRCULATION CENTERS SINCE THE
LOW-LEVEL CENTER WILL LIKELY BE LEFT WELL BEHIND NEAR THE MEXICAN
COAST DUE TO THE HIGH MOUNTAINOUS TERRAIN AND STRONG UPPER-LEVEL
SHEAR. RESIDUAL MOISTURE FROM THIS CYCLONE WILL LIKELY SPREAD
ACROSS NORTHEASTERN MEXICO AND TEXAS ENHANCING THE RAINFALL
POTENTIAL ACROSS THOSE AREAS BY DAY 5...AND PERHAPS BEYOND.

THE DEPRESSION POSSESSES A SMALL TIGHT LOW-LEVEL CIRCULATION AND AN
IMPRESSIVE MID-LEVEL CIRCULATION. HOWEVER...EASTERLY MID-LEVEL
SHEAR UNDERCUTTING THE FAVORABLE UPPER-LEVEL OUTFLOW IS TILTING THE
VORTEX TOWARD THE WEST. THIS PATTERN IS EXPECTED TO PERSIST FOR THE
NEXT 24-36 HOURS...SO ONLY SLOW INTENSIFICATION IS EXPECTED DURING
THAT TIME. AFTERWARD...THE SHEAR IS FORECAST TO DECREASE AND MORE
SIGNIFICANT INTENSIFICATION IS EXPECTED UNTIL 96 HOURS WHEN
INCREASING SOUTHWESTERLY SHEAR SHOULD INDUCE GRADUAL WEAKENING.

FORECAST POSITIONS AND MAX WINDS
 
INITIAL      21/0900Z 15.5N 105.9W    30 KT
 12HR VT     21/1800Z 15.4N 107.4W    35 KT
 24HR VT     22/0600Z 15.1N 108.4W    40 KT
 36HR VT     22/1800Z 15.2N 109.2W    45 KT
 48HR VT     23/0600Z 16.0N 110.0W    55 KT
 72HR VT     24/0600Z 18.0N 110.5W    65 KT
 96HR VT     25/0600Z 22.0N 109.0W    55 KT
120HR VT     26/0600Z 27.0N 103.0W    20 KT...DISSIPATING INLAND
 
$$
FORECASTER STEWART
 
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