Tropical Storm SONGDA Advisory Tue Oct 11

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 23W (SONGDA) WARNING NR 09//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TYPHOON 23W (SONGDA), LOCATED APPROXIMATELY 253 NM EAST OF IWO
TO, HAS TRACKED NORTH-NORTHWESTWARD AT 10 KNOTS OVER THE PAST SIX
HOURS. ANIMATED MULTISPECTRAL SATELLITE IMAGERY DEPICTS A RAPIDLY
CONSOLIDATING SYSTEM WITH DEEP CENTRAL CONVECTION AND A NEWLY FORMED
12 NM RAGGED EYE GIVING HIGH CONFIDENCE TO THE INITIAL POSITION. A
100316Z GMI 89 GHZ IMAGE SHOWS VERY SHALLOW CONVECTION IN THE
BANDING FEATURES, BUT A SOLID RING OF DEEP CONVECTION AROUND THE LOW
LEVEL CIRCULATION CENTER MEASURING ONLY ABOUT 50 NM IN DIAMETER. THE
INITIAL INTENSITY ASSESSMENT OF 90 KNOTS IS BASED ON DVORAK
ESTIMATES OF T5.0 (90 KNOTS) FROM ALL AGENCIES. UPPER-LEVEL ANALYSIS
SHOWS NEAR RADIAL OUTFLOW BEING LIMITED ON THE SOUTHERN PORTION,
WITH A VERY STRONG POLEWARD TAP INTO THE MIDLATITUDE WESTERLIES, AND
ACCOMPANIED BY VERY LOW VERTICAL WIND SHEAR. SSTS ARE FAVORABLE NEAR
28 CELSIUS. CURRENTLY TY SONGDA IS TRACKING NORTH-NORTHWEST ALONG
THE PERIPHERY OF A SUBTROPICAL RIDGE TO THE NORTHEAST, AND SLOWING
SLIGHTLY AS IT APPROACHES THE RIDGE AXIS.
3. FORECAST REASONING.
   A.  NO SIGNIFICANT CHANGE TO THE FORECAST PHILOSOPHY FROM THE
PREVIOUS PROGNOSTIC REASONING MESSAGE.
   B. TY SONGDA WILL TRACK NORTHWARD AS IT ROUNDS THE CURRENT
STEERING RIDGE AXIS IN THE NEXT 12 TO 24 HOURS, EVENTUALLY SHIFTING
TO A NORTHEASTWARD TRACK. OUTFLOW IS EXPECTED TO IMPROVE DURING THIS
TIME AS THE SYSTEM APPROACHES MIDLATITUDE WESTERLIES AND AN
APPROACHING SHORTWAVE TROUGH TO THE WEST GIVING A SHORT WINDOW FOR
FURTHER INTENSIFICATION, AND REACHING A PEAK INTENSITY OF 100 KNOTS.
BEYOND TAU 24 TY SONGDA WILL BEGIN TO INTERACT WITH THE APPROACHING
TROUGH AND WESTERLY JET AND IS EXPECTED TO BEGIN WEAKENING AS SHEAR
VALUES INCREASE. BY TAU 36 TO 48 TY SONGDA WILL BEGIN TO EXHIBIT
FRONTAL CHARACTERISTICS AS IT GETS ABSORBED INTO BAROCLINIC ZONE AND
TRANSITIONS INTO AN EXTRATROPICAL SYSTEM. TY SONGDA IS EXPECTED TO
BECOME FULLY EXTRATROPICAL BY TAU 72. DYNAMIC MODEL GUIDANCE IS
STILL IN VERY GOOD AGREEMENT, LENDING HIGH CONFIDENCE TO THE
FORECAST TRACK.//
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