WDPN33 PGTW 221500
MSGID/GENADMIN/NAVMARFCSTCEN PEARL HARBOR HI/JTWC//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 17W (SEVENTEEN) 
WARNING NR 04//
RMKS/
1. FOR METEOROLOGISTS.
2. 12 HOUR SUMMARY AND ANALYSIS.
    A. TROPICAL DEPRESSION (TD) 17W (SEVENTEEN), LOCATED 
APPROXIMATELY 620 NM NORTHEAST OF SAIPAN, HAS TRACKED NORTHWESTWARD 
AT 10 KNOTS OVER THE PAST SIX HOURS. ANIMATED INFRARED SATELLITE 
IMAGERY AND A 221136Z TRMM MICROWAVE PASS DEPICT TIGHTLY CURVED LOW 
LEVEL BANDING WRAPPING INTO THE SYSTEM CENTER WITH A MAJORITY OF THE 
DEEP CONVECTION BEING SHEARED TO THE SOUTHWEST. THERE IS FAIR 
CONFIDENCE IN THE CURRENT POSITION BASED ON THE AFOREMENTIONED TRMM 
PASS. THE CURRENT INTENSITY ESTIMATE OF 30 KNOTS IS CONSISTENT WITH 
DVORAK ESTIMATES FROM PGTW AND KNES AT 221130Z AS WELL AS A 221132Z 
ASCAT PASS INDICATING 25 TO 30 KNOT WINDS. UPPER LEVEL ANALYSIS 
INDICATES TD 17W IS IN A MARGINAL ENVIRONMENT FOR FURTHER 
DEVELOPMENT, WITH STRONG DIFFLUENCE ALOFT AND MODERATE NORTHEASTERLY 
VERTICAL WIND SHEAR. TD 15W IS CURRENTLY TRACKING NORTHWESTWARD 
UNDER THE INFLUENCE OF A LOW TO MID-LEVEL SUBTROPICAL STEERING RIDGE.
3. FORECAST REASONING.
    A. THERE IS NO SIGNIFICANT CHANGE IN THE FORECAST REASONING 
SINCE THE PREVIOUS BULLETIN.
    B. TD 17W IS FORECAST TO BEGIN TURNING POLEWARD WITHIN THE NEXT 
12 HOURS AS THE SUBTROPICAL STEERING RIDGE IS WEAKENED BY A 
TRANSITORY MID-LATITUDE TROUGH. AFTER TAU 12, THE SYSTEM IS EXPECTED 
TO TRACK NORTHEASTWARD AHEAD OF A DIGGING MID-LEVEL TROUGH AND 
WEAKEN TO BELOW WARNING CRITERIA BY TAU 36. THE AVAILABLE NUMERICAL 
MODEL GUIDANCE IS IN GOOD AGREEMENT WITH THE EXCEPTION OF WBAR WHICH 
LOOPS THE SYSTEM TO THE SOUTH, INDICATIVE OF A WEAK STEERING 
ENVIRONMENT. THIS FORECAST IS SLIGHTLY NORTH OF CONSENSUS AND FAVORS 
A SLOWER POLEWARD TURN AHEAD OF THE TROUGH.//
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