Tropical Storm SAOLA Advisory Tue Oct 24

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 27W (TWENTYSEVEN)
WARNING NR 15//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TROPICAL DEPRESSION 27W (TWENTYSEVEN), LOCATED APPROXIMATELY 297
NM SOUTH-SOUTHEAST OF ANDERSEN AFB, HAS TRACKED WEST-NORTHWESTWARD
AT 04 KNOTS OVER THE PAST SIX HOURS. ANIMATED MULTISPECTRAL
SATELLITE IMAGERY DEPICTS A BROAD AND DISORGANIZED AREA OF DEEP
CONVECTION STRUGGLING TO CONSOLIDATE ABOUT AN OBSCURED LOW LEVEL
CIRCULATION CENTER (LLCC). THE INITIAL POSITION IS BASED ON
SATELLITE FIXES WITH LOW CONFIDENCE DUE TO DISORGANIZED CONVECTION.
THE INITIAL INTENSITY IS ASSESSED AT 30 KNOTS AND IS HEDGED HIGER
THAN AGENCY DVORAK ESTIMATES OF T1.5 (25 KNOTS) BASED ON PERSISTENCE
AND A 222314Z OSCAT IMAGE SHOWING SPORADIC AREAS OF 30 KNOTS
SURROUNDING THE LLCC. THE OSCAT IMAGE ALSO SHOWS A REGION OF 40
KNOTS EMBEDDED WITHIN THE CONVECTIVE BANDS APPROXIMATELY 220 NM TO
THE SOUTHWEST OF THE LLCC. UPPER-LEVEL ANALYSIS SHOWS IMPROVEMENT
OVER THE LAST SIX HOURS DUE TO A DECREASE IN EASTERLY FLOW AS A WEAK
INVERTED TROUGH IS DEVELOPING UPSTREAM. VERTICAL WIND SHEAR IS
DECREASING INTO THE MARGINAL TO FAVORABLE CATEGORY. SSTS IN THE
REGION ARE ALSO VERY WARM NEAR 30 CELSIUS. CURRENTLY TD 27W IS
TRACKING WEST-NORTHWEST ALONG THE SOUTHWESTERN BOUNDARY OF A
BUILDING MID-TO-LOW LEVEL SUBTROPICAL RIDGE (STR) TO THE
NORTHEAST.
3. FORECAST REASONING.
   A. THE FORECAST PHILOSOPHY HAS CHANGED SLIGHTLY TO REFLECT A MORE
WESTWARD TRACK WITH AN EARLIER PERIOD OF INTENSIFICATION FOLLOWED BY
A WEAKENING TREND IN THE LATER TAUS.
   B. THE STR WILL CONTINUE TO STRENGTHEN OVER THE 24 TO 36 HOURS
WHICH WILL ACCELERATE TD 27W TO THE NORTHWEST. THE EASTERN TUTT WILL
ADVERSELY INFLUENCE OUTFLOW AND CONSOLIDATION OVER THE NEXT 24
HOURS, BUT THEREAFTER CONDITIONS ALOFT WILL SHOW GREAT IMPROVEMENT
AND TD 27 IS FORECAST TO INTENSIFY AT THE CLIMATOLOGICAL AVERAGE
REACHING A PEAK INTENSITY OF 90 KNOTS BY TAU 72. DYNAMIC MODEL
GUIDANCE SHOWS A WIDE RANGE OF TRACK POSSIBILITIES IN THE EARLY TAUS
RELATED TO THE RATE OF INTENSIFICATION. THE JAPANESE MODELS AND
NAVGEM KEEP THE SYSTEM AS A TROPICAL DEPRESSION THROUGH TAU 36 AND
FAVOR A MORE EASTWARD TRACK. GFS AND HWRF ARE SHOWING A MORE
AGGRESSIVE RATE OF INTENSIFICATION THROUGH TAU 36 AND FAVOR THE FAR
WESTWARD TRACK SOLUTIONS. THE JTWC FORECAST TRACK THROUGH TAU 48 IS
CONSISTENT WITH THE INTENSITY FORECAST, FOLLOWING A TRACK NEAR THE
MULTI-MODEL CONSENSUS HEDGED TOWARD GFS AND HWRF WITH FAIR
CONFIDENCE.
   C. IN THE EXTENDED PERIOD, THERE IS FURTHER UNCERTAINTY DUE TO A
SHORT WAVE TROUGH DEVELOPING AROUND TAU 48 THROUG 72, PASSING
POLEWARD OF TD 27W. AS A RESULT OF THE TROUGH PASSING THROUGH, THE
MID-LEVEL RIDGE WILL BE ERODED TO SOME DEGREE AND UPPER-LEVEL
OUTFLOW WILL BE ENHANCED HELPING TD 27W TO REACH THE PEAK 90 KNOT
INTENSITY. BEYOND TAU 72 THE STR IS FORECAST TO AGAIN STRENGTHEN
RESTRICTING THE EQUATORWARD OUTFLOW CHANNEL FROM ENHANCED
SOUTHEASTERLY FLOW ALOFT. STRONG ZONAL FLOW FROM THE THE MID-
LATITUDE JET POSITIONED OVER SOUTHERN JAPAN IS ALSO FORECAST TO
INCREASE VERTICAL WIND SHEAR LEADING TO A WEAKENING TREND BEYOND TAU
96, AND SHOULD KEEP THE TRACK BEYOND TAU 120 SOUTH OF JAPAN.
AVAILABLE MODEL GUIDANCE SHOWS MUCH LARGER SEPARATION IN THE LATER
TAUS AS A RESULT OF THE DISPARITY IN INTENSITIES BETWEEN MODELS,
DEPENDENT ON STEERING LEVELS, AND THE TROUGH-RIDGE INTERACTION
AROUND TAU 48. THE GFS SOLUTION IS STILL THE FURTHEST WESTWARD
OUTLIER WITH NAVGEM AND THE JAPANESE MODELS SHOWING AN UNREALISTIC
EASTWARD TURN INTO THE STEERING RIDGE. THE JTWC FORECAST TRACK IS
NEAR THE MULTI-MODEL CONSENSUS HEDGED TOWARD THE GFS SOLUTION WITH
LOW CONFIDENCE.//
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