TC 22S(HALIMA): forecast to reach CAT 4 US by 36h, 24/15utc

JTWC IS ISSUING 12HOURLY WARNINGS ON TC 22S(HALIMA).3HOURLY SATELLITE BULLETINS ARE ISSUED FOR TC 22S AND THE REMNANTS OF TC 21S(CHARMOTTE).

24/15UTC.

3. FORECAST REASONING. SIGNIFICANT FORECAST CHANGES: THERE ARE NO SIGNIFICANT CHANGES TO THE FORECAST FROM THE PREVIOUS WARNING. FORECAST DISCUSSION: TC 22S IS FORECAST TO TRACK GENERALLY SOUTHWARD ALONG THE WESTERN PERIPHERY OF A NORTH-SOUTH ORIENTED STEERING RIDGE THROUGH 48H. DUE TO HIGHLY FAVORABLE CONDITIONS, THE SYSTEM IS EXPECTED TO RAPIDLY INTENSIFY THROUGH 36H WITH A PEAK INTENSITY OF 115 KNOTS/CAT 4 US AT 36H. SLIGHT WEAKENING WILL OCCUR AFTER 36H AS VERTICAL WIND SHEAR (VWS) INCREASES TO MODERATE LEVELS WITH THE APPROACH OF A BROAD UPPER-LEVEL TROUGH OVER THE SYSTEM. AFTER 48H, TC 22S WILL TURN SOUTH-SOUTHEASTWARD THEN EAST-SOUTHEASTWARD THROUGH 96H AS IT TRACKS WITHIN THE EVOLVING FLOW BETWEEN THE EASTWARD-PROPAGATING, UPPER-LEVEL TROUGH AND THE SHIFTING STEERING RIDGE TO THE NORTHEAST. AFTER 96H, A STRONG LOW- TO MID-LEVEL HIGH WILL BUILD TO THE SOUTHEAST EFFECTIVELY BLOCKING THE EASTWARD PROGRESSION AND PRODUCING A SLOWER, MORE ERRATIC TRACK. TC HALIMA WILL STEADILY WEAKEN THROUGH THE REMAINDER OF THE FORECAST AS VWS INCREASES TO HIGH LEVELS (25-35 KNOTS) AND SEA SURFACE TEMPERATURES COOL TO 26-27C. TC 22S SHOULD GRADUALLY TRANSITION TO A SUBTROPICAL STORM IN THE EXTENDED PERIOD AS IT STALLS UNDER THE SUBTROPICAL WESTERLIES.

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION: ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS AN 150KM DIAMETER CENTRAL DENSE OVERCAST OBSCURING THE LOW-LEVEL CIRCULATION CENTER (LLCC) WITH SPIRAL BANDING PRIMARILY LOCATED OVER THE WESTERN SEMICIRCLE. A 241057Z SSMIS 91GHZ MICROWAVE IMAGE SHOWS TIGHTLY CURVED BANDING WRAPPING INTO THE EYEWALL SURROUNDING A SMALL 9-19KM MICROWAVE EYE FEATURE, WHICH SUPPORTS THE INITIAL POSITION WITH HIGH CONFIDENCE. UPPER-LEVEL CONDITIONS REMAIN HIGHLY FAVORABLE WITH NEAR-RADIAL OUTFLOW AND ROBUST POLEWARD OUTFLOW INTO THE STRONG WESTERLIES TO THE SOUTH. OUTFLOW OVER THE EASTERN QUADRANT IS GRADUALLY IMPROVING DESPITE SOME LOW EASTERLY VERTICAL WIND SHEAR. THERE IS MEDIUM CONFIDENCE IN THE INITIAL INTENSITY OF 65 KNOTS/CAT 1 US, WHICH IS BASED ON THE HIGHER END OF THE DVORAK ESTIMATES RANGING FROM 55 TO 65 KNOTS AND THE CIMSS ADT ESTIMATE.

MODEL DISCUSSION: NUMERICAL MODEL GUIDANCE IS IN FAIR AGREEMENT THROUGH 72H WITH A 370KM SPREAD IN SOLUTIONS AT 72H. SIGNIFICANT UNCERTAINTY IS PRIMARILY RELATED TO THE COMPLEX, EVOLVING STEERING PATTERN ASSOCIATED WITH AN APPROACHING UPPER-LEVEL TROUGH. AFTER 72H, BOTH THE DETERMINISTIC AND PROBABILISTIC MODEL GUIDANCE INDICATE INCREASING UNCERTAINTY (LOW JTWC TRACK CONFIDENCE) DUE TO A POTENTIAL SLOW-DOWN OR STALL ASSOCIATED WITH A STRONG HIGH FORECAST TO BUILD IN QUICKLY TO THE EAST AND SOUTHEAST. INTENSITY GUIDANCE IS FAIRLY UNANIMOUS IN SUPPORTING RAPID INTENSIFICATION (RI) OVER THE NEXT 36 HOURS WITH SEVERAL RAPID INTENSIFICATION AIDS TRIGGERED AND THE COAMPS-TC ENSEMBLE (GFS VERSION) INDICATING A 60 TO 80 PERCENT PROBABILITY OF RI. IN THE EXTENDED FORECAST, THERE IS LOW CONFIDENCE IN THE JTWC INTENSITY FORECAST WITH POTENTIAL FOR A SIGNIFICANTLY WEAKER SYSTEM.