Tropical Storm ATSANI Advisory 10月30日

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 23W (ATSANI)
WARNING NR 002//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TROPICAL DEPRESSION 23W (ATSANI), LOCATED APPROXIMATELY 297 NM
SOUTH-SOUTHEAST OF ANDERSEN AFB, GUAM HAS TRACKED NORTH-
NORTHWESTWARD AT 13 KNOTS OVER THE PAST SIX HOURS. ANIMATED ENHANCED
INFRARED SATELLITE IMAGERY DEPICTS A BROAD AREA OF GENERALLY
DISORGANIZED DEEP CONVECTIVE ACTIVITY. A 291610Z AMSR2 89 GHZ PASS
SUGGESTS THE LOW LEVEL CIRCULATION CENTER (LLCC) MAY BE
CONSOLIDATING AROUND A DEVELOPING VERTICAL TOWER NEAR THE CENTER OF
THE CONVECTIVE MASS, WHILE ACTIVITY ALONG THE NORTHERN PERIPHERY
APPEARS LINEAR AND NOT WRAPPING. THE CIMSS 850 MB VORTICITY PRODUCT
ALSO DEPICTS THE CURRENT STRUCTURE ASYMMETRY. THERE IS A HIGH DEGREE
OF UNCERTAINTY IN THE INITIAL PLACEMENT AS THE LLCC IS NOT FIRMLY
ESTABLISHED AND MAY SHIFT. THE INITIAL POSITION IS BASED ON FIXES
FROM PGTW AND RJTD, AND THE AFOREMENTIONED AMSR2 DATA. THE INITIAL
INTENSITY IS ASSESSED AT 25 KTS BASED ON SUBJECTIVE DVORAK
ESTIMATES. THE AMSR2 WIND SPEED PRODUCT INDICATES AN ISOLATED AREA
OF 30 TO 34 KNOT WINDS TO THE EAST, HOWEVER, AN EARLIER SCAT PASS
AND CURRENT STRUCTURE ANALYSIS INDICATES THESE ISOLATED HIGHER WINDS
ARE NOT REPRESENTATIVE OF THE SYSTEM’S OVERALL DEVELOPMENT AT THIS
TIME. UPPER LEVEL ANALYSIS INDICATES MODERATE (15-20 KNOT) VERTICAL
WIND SHEAR OVER THE SYSTEM MAY BE HAMPERING DEVELOPMENT, HOWEVER,
THIS IS PARTIALLY OFFSET BY DIVERGENCE OVER THE LLCC. 30 TO 31
DEGREE CELSIUS SEA SURFACE TEMPERATURES ARE VERY FAVORABLE. TD 23 IS
CURRENTLY TRACKING GENERALLY NORTHWESTWARD ALONG A RIDGE OF HIGH
PRESSURE TO THE EAST.
3. FORECAST REASONING.
   A. NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE PREVIOUS
PROGNOSTIC REASONING MESSAGE.
   B. TD 23W IS FORECAST TO CONTINUE ITS PIVOT TO A MORE
NORTHWESTWARD TRACK OVER THE NEXT 12 HOURS, AS THE STEERING RIDGE
REORIENTS SLIGHTLY, AND IS FORECAST TO CONTINUE THIS NORTHWESTWARD
TRACK THROUGH TAU 72. AS THE SYSTEM TRACKS NORTHWESTWARD, IT WILL
BEGIN TO BE IMPACTED BY THE OUTFLOW FROM TY 22W, WITH CONVERGENT
UPPER-LEVEL FLOW MOVING DOWN FROM THE NORTH LIMITING THE AVAILABLE
OUTFLOW TO A SINGLE WESTWARD CHANNEL. THIS, COMBINED WITH MODERATE
VWS WILL OFFSET THE VERY WARM (30 DEG CELSIUS) WATERS TO LIMIT THE
SYSTEM’S INTENSIFICATION THROUGH TAU 48. AFTER TAU 48 THE UPPER-
LEVEL PATTERN WILL BEGIN TO SHIFT AND PROVIDE INCREASING DIVERGENT
OUTFLOW ALLOWING THE SYSTEM TO START INTENSIFYING AT A FASTER RATE,
INCREASING TO 80 KNOTS BY TAU 72. THE JTWC FORECAST TRACK IS PLACED
WITH HIGH CONFIDENCE THROUGH TAU 48 AND LIES SLIGHTLY SOUTH OF THE
MULTI-MODEL CONSENSUS TO ACCOUNT FOR JGSM, WHICH IS FAR TO THE NORTH
OF THE REMAINDER OF THE MODELS AT TAU 48. HOWEVER, NUMERICAL MODEL
GUIDANCE DIVERGES MORE AFTER TAU 48 LEADING TO MODERATE CONFIDENCE
BETWEEN TAUS 48-72 WITH CROSS-TRACK SPREAD INCREASING TO 250 NM AT
TAU 72 WITH AFUM AND GFS REPRESENTING THE NORTH AND SOUTH
OUTLIERS.//
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