Tropical Storm SONGDA Advisory Sa, 08.10.

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 23W (TWENTYTHREE)
WARNING NR 01//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
TROPICAL DEPRESSION 23W (TWENTYTHREE), LOCATED APPROXIMATELY 866 NM
EAST-SOUTHEAST OF IWO TO, HAS TRACKED WEST-NORTHWESTWARD AT 15 KNOTS
OVER THE PAST SIX HOURS. ANIMATED MULTISPECTRAL SATELLITE IMAGERY
AND A 080202Z AMSR2 IMAGE DEPICTS AN AREA OF IMPROVING CONSOLIDATION
WITH FORMATIVE BANDING ON THE NORTH AND WESTERN PERIPHERIES WRAPPING
INTO THE LOW LEVEL CIRCULATION CENTER GIVING HIGH CONFIDENCE TO THE
INITIAL POSITION. THE INITIAL INTENSITY IS ASSESSED AT 25 KNOTS AND
IS BASED ON THE IMPROVED CONVECTIVE STRUCTURE AND DVORAK ESTIMATES
RANGING FROM T1.5 TO T2.0 (25 TO 30 KNOTS). UPPER-LEVEL ANALYSIS
SHOWS IMPROVING POLEWARD OUTFLOW, BUT THE PRESENCE OF A TROPICAL
UPPER TROPOSPHERIC TROUGH (TUTT) TO THE SOUTHWEST IS IMPINGING ON
EQUATORWARD OUTFLOW AND ESTABLISHMENT OF DEEP CONVECTION ON THE
SOUTHERN PERIPHERY. VERTICAL WIND SHEAR IS FAVORABLE AT 10 TO 15
KNOTS, AND SEA SURFACE TEMPERATURES ARE NEAR 29 CELSIUS. CURRENTLY
TD 23W  IS TRACKING WEST-NORTHWESTWARD ALONG THE SOUTHERN PERIPHERY
OF A DEEP-LAYERED SUBTROPICAL RIDGE.
3. FORECAST REASONING.
   A. THIS IS THE FIRST PROGNOSTIC REASONING MESSAGE AND
SETS THE FORECAST PHILOSOPHY.
   B. TD 23W WILL CONTINUE ON A TRACK NORTHWEST ALONG THE CURRENT
STEERING RIDGE. THE SOUTHERN POSITIONED TUTT WILL CONTINUE TO
INFLUENCE THE SYSTEM FOR THE NEXT 24 TO 36 HOURS, HOWEVER, UPPER-
LEVEL CONDITIONS ARE EXPECTED TO IMPROVE AS THE TUTT EVENTUALLY
MOVES OFF TO THE SOUTHWEST. FOR THIS REASON GRADUAL INTENSIFICATION
IS EXPECTED THROUGH TAU 48. BETWEEN TAU 48 AND 72, TD 23W WILL SLOW
AS IT ROUNDS THE RIDGE AXIS AND BEGINS TO TAP INTO THE WESTERLY JET
TO THE NORTH. THE PEAK INTENSITY IS EXPECTED TO REACH 75 KNOTS
DURING THIS TIME.
   C. IN THE EXTENDED FORECAST PERIOD, TD 23W WILL TURN TO THE
NORTHEAST AFTER ROUNDING THE STEERING RIDGE AXIS. THE SYSTEM WILL
ACCELERATE AND EXPERIENCE HIGHER WIND SHEAR VALUES AS IT APPROACHES
THE STRONG WESTERLY FLOW. BY TAU 120 TD 23W WILL BEGIN EXTRATROPICAL
TRANSITION AS IT INTERACTS WITH THE BAROCLINIC ZONE. DYNAMIC MODEL
GUIDANCE IS IN GOOD AGREEMENT WITH THE FORECAST PHILOSOPHY DIFFERING
SLIGHTLY IN THE EXACT POSITION AND TIMING IN THE TURN TO THE
NORTHWEST, LENDING HIGH CONFIDENCE TO THE FORECAST TRACK.//
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