MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 01C (HALOLA) WARNING NR
31//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
TROPICAL STORM (TS) 01C (HALOLA), LOCATED APPROXIMATELY 955 NM
EAST-SOUTHEAST OF IWO TO, HAS TRACKED WESTWARD AT 12 KNOTS OVER THE
PAST SIX HOURS. ANIMATED INFRARED SATELLITE IMAGERY DEPICTS
PERSISTENT DEEP CONVECTION OVER A PARTIALLY-EXPOSED LOW-LEVEL
CIRCULATION CENTER (LLCC). A 171652Z SSMI 37 GHZ IMAGE SHOWS LIMITED
CURVED BANDING OVER THE SOUTHERN QUADRANT OF THE LLCC, WHICH IS
LOCATED ON THE WESTERN EDGE OF THE DEEP CONVECTION. THE SSMI IMAGE
PROVIDES GOOD CONFIDENCE IN THE CURRENT POSITION. A 171016Z BYU HI-
RESOLUTION ASCAT IMAGE REVEALS 30 TO 35 KNOT WINDS OVER THE NORTHERN
SEMI-CIRCLE OF THE CIRCULATION WITH WEAKER WINDS OVER THE SOUTHERN
SEMI-CIRCLE. BASED ON ASCAT DATA AND DVORAK INTENSITY ESTIMATES, THE
CURRENT INTENSITY IS ASSESSED AT 35 KNOTS. UPPER-LEVEL ANALYSIS
INDICATES A MARGINAL ENVIRONMENT DUE TO THE CLOSE PROXIMITY OF A
TUTT CELL NEAR 21N 163E, WHICH IS PRODUCING CONVERGENT FLOW OVER THE
NORTHERN SEMI-CIRCLE AND WESTERLY VERTICAL WIND SHEAR. TS 01C IS
TRACKING ALONG THE SOUTHERN PERIPHERY OF THE DEEP-LAYERED STR.
3. FORECAST REASONING.
A. THERE IS NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE
PREVIOUS PROGNOSTIC REASONING MESSAGE.
B. TS 01C WILL CONTINUE TRACKING WESTWARD TO WEST-NORTHWESTWARD
UNDER THE STEERING INFLUENCE OF THE STR THROUGH TAU 72. AVAILABLE
DYNAMIC GUIDANCE IS IN TIGHT AGREEMENT WITH A SPREAD OF 110 NM AT
TAU 72, THEREFORE HIGH CONFIDENCE IN THE JTWC FORECAST TRACK THROUGH
TAU 72. TS 01C IS STRUGGLING DUE TO THE MARGINAL UPPER-LEVEL
ENVIRONMENT AND POSSIBLE DRY AIR ENTRAINMENT, THEREFORE, THE SYSTEM
IS FORECAST TO MAINTAIN INTENSITY THROUGH TAU 12 WITH A SLOW RATE OF
INTENSIFICATION FROM TAU 12 TO 48. DUE TO THE WEAK NATURE OF THE
SYSTEM AND THE STRONG LOW-LEVEL STR, THE SYSTEM IS EXPECTED TO
MAINTAIN A GENERALLY WESTWARD TRACK THROUGH TAU 24. THEREAFTER, THE
SYSTEM SHOULD TURN MORE WEST-NORTHWESTWARD AS IT INTENSIFIES AND
BECOMES BETTER ORGANIZED. FORECAST GUIDANCE INDICATES MARGINAL
CONDITIONS THROUGH, AT LEAST, TAU 48; HOWEVER, THERE IS UNCERTAINTY
IN THE INTENSITY FORECAST DUE TO THE COMPLEX INTERACTION WITH THE
TUTT.
C. IN THE EXTENDED FORECAST PERIOD, EXPECT A MORE WEST-
NORTHWESTWARD TO NORTHWESTWARD TRACK AS THE SYSTEM BEGINS TO
APPROACH THE WESTERN PERIPHERY OF THE STR. DYNAMIC MODEL GUIDANCE
DIVERGES SIGNIFICANTLY WITH THE MESO-SCALE MODELS SHOWING A SHARPER
NORTHWESTWARD TURN THAN THE GLOBAL MODELS, WHICH SHOW A MORE WEST-
NORTHWESTWARD TRACK. THERE IS A 390-NM SPREAD IN SOLUTIONS AT TAU
120, THEREFORE, UNCERTAINTY IS HIGH AND CONFIDENCE IN THE JTWC
FORECAST TRACK IS LOW. INTENSIFICATION IS MORE LIKELY DUE TO
IMPROVED POLEWARD OUTFLOW WITH A PEAK INTENSITY OF 80 KNOTS FORECAST
AT TAU 96 AND 120.//
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