TC 19S(GOMBE): intensifying rapidly next 18h: dangerous CAT 3 US at landfall/Mozambique,destructive flooding likely once inland//Invest 99S, 10/09utc

JTWC IS ISSUING 6HOURLY WARNINGS AND 3HOURLY SATELLITE BULLETINS ON TC 19S(GOMBE).

10/09UTC.

FORECAST REASONING. SIGNIFICANT FORECAST CHANGES: THERE ARE NO SIGNIFICANT CHANGES TO THE FORECAST FROM THE PREVIOUS WARNING. HOWEVER THE FORECAST TIMELINE HAS BEEN EXTENDED TO 120 HOURS, TO CAPTURE THE RETURN OF THE SYSTEM OVER WATER AND SUBSEQUENT REINTENSIFICATION. FORECAST DISCUSSION: TC 19S IS TRACKING WESTWARD IN A WELL-BEHAVED MANNER ALONG THE NORTHERN SIDE OF A WELL-ENTRENCHED AND STRONG DEEP-LAYER SUBTROPICAL RIDGE (STR) TO THE SOUTH. NO SIGNIFICANT CHANGE IS EXPECTED IN THIS GENERAL MOTION THROUGH 48H, THOUGH THE SYSTEM IS FORECAST TO SLOW DOWN AS IT MAKES LANDFALL AROUND 18H AND MOVES INLAND OVER MOZAMBIQUE. CONDITIONS ARE HIGHLY FAVORABLE WITH LOW VWS, WARM SSTS AND ROBUST RADIAL OUTFLOW, AND SUPPORT RAPID INTENSIFICATION PRIOR TO LANDFALL. WITH THE FORECAST POINTS FALLING ON EITHER SIDE OF LANDFALL, THE PEAK INTENSITY IS NOT CAPTURED IN THE FORECAST TRACK ITSELF, AND THE PEAK INTENSITY IS PREDICTED TO OCCUR JUST PRIOR TO LANDFALL, NEAR 18H, AT 100-105 KNOTS/CAT 3 US. AFTER MOVING INLAND AND RAPIDLY WEAKENING, TC 19S WILL SLOW TO A CRAWL AS THE STEERING RIDGE WEAKENS AND MOVES EAST RESULTING IN A WEAK STEERING ENVIRONMENT. THE STALLING OF THE SYSTEM WILL LIKELY BRING SIGNIFICANT AND DESTRUCTIVE FLOODING TO CENTRAL MOZAMBIQUE. THE APPROACH OF A MID-LATITUDE TROUGH FROM THE WEST WILL QUICKLY ERODE THE RIDGE FROM THE WEST, BUT SIMULTANEOUSLY THE RIDGE WILL REORIENT TO A NORTH-SOUTH AXIS AND IN RESPONSE, THE REMNANTS OF TC 19S WILL TURN SHARPLY SOUTHWARD BY 72H. THE SYSTEM IS FORECAST TO WEAKEN TO 30 KNOTS, AND POTENTIALLY SLIGHTLY LESS BY 72H. HOWEVER, IT HAS BECOME INCREASINGLY LIKELY THAT THE REMNANTS WILL EMERGE BACK OVER THE MOZAMBIQUE CHANNEL BY 96H, WHERE THE FAVORABLE ENVIRONMENTAL CONDITIONS WILL SUPPORT REINTENSIFICATION TO AT LEAST 45 KNOTS BY 120H.

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION: ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS A VERY COMPACT AREA OF DEEP, INCREASINGLY ORGANIZED CONVECTIVE ACTIVITY WHICH HAS DEVELOPED INTO A CDO. VORTICAL HOT TOWERS WITH OVERSHOOTING TOPS WERE EVIDENT BY THE 100700Z HOUR, AND ARE BEGINNING TO SURROUND A NASCENT WARM SPOT IN THE INFRARED IMAGERY. ADDITIONALLY, GLOBAL LIGHTNING DATA SHOWS AN INCREASED INNER-CORE LIGHTNING ACTIVITY, ALL OF WHICH INDICATES THE SYSTEM CONTINUES TO INTENSIFY AND SUGGESTS THAT THE SYSTEM WILL SOON DEVELOP AN ACTUAL EYE FEATURE AND COMMENCE RAPID INTENSIFICATION. A 100618Z AMSU-B 89GHZ MICROWAVE IMAGE SHOWS THE SMALL CORE SURROUNDED BY DEEP CONVECTIVE BANDING, THOUGH THE LOW RESOLUTION PROHIBITS CLARIFICATION OF A MICROWAVE EYE FEATURE. THE INITIAL POSITION IS ASSESSED WITH HIGH CONFIDENCE BASED ON THE AMSU-B IMAGERY IN CONJUNCTION WITH THE PGTW AND FMEE FIX POSITIONS. THE INITIAL INTENSITY IS ASSESSED WITH HIGH CONFIDENCE BASED ON THE AVERAGE OF DVORAK INTENSITY ESTIMATES BETWEEN 55KT AND 77 KTS AND SLIGHTLY HIGHER THAN THE ADT AND SATCON IN LIGHT OF A 100258Z SMAP PASS WHICH SHOWED A 63 KNOT 10-MIN MAXIMUM WIND.

MODEL DISCUSSION: DETERMINISTIC AND ENSEMBLE TRACK GUIDANCE PROVIDES HIGH CONFIDENCE TO THE JTWC FORECAST TRACK THROUGH 48H, WITH A MINIMAL MODEL SPREAD OF 65KM BY 48H. AFTER THIS POINT HOWEVER, MODEL GUIDANCE DIVERGES SIGNIFICANTLY AND RAPIDLY, WITH THE HWRF AND NAVGEM SOLUTIONS KEEPING THE SYSTEM QUASI-STATIONARY AFTER 48H AND DISSIPATING IT OVER LAND. THE REMAINDER OF THE GUIDANCE INDICATES A SHARP TURN TO THE SOUTH, BUT DIFFERS ON THE TIMING AND SHARPNESS OF THE TURN. OVERALL CONFIDENCE IN THE LONGER TERM FORECAST IS LOW, WITH CROSS-TRACK SPREAD INCREASING TO NEARLY 370KM BY TAU 120H. INTENSITY GUIDANCE SUPPORTS THE FORECAST PHILOSOPHY BUT THE MESOSCALE MODELS HAVE BACKED OFF THE PEAK INTENSITY WITH THIS RUN, WITH THE HWRF AND COAMPS-TC NOW PEAKING THE SYSTEM AT ONLY 85 KNOTS. HOWEVER THE DECAY SHIPS STILL INDICATES A 100 KNOT PEAK, AND THE RAPID INTENSIFICATION GUIDANCE INCLUDING RIPA AND RIDE ARE STILL BEING TRIGGERED AND PROVIDES INCREASED CONFIDENCE TO THE FORECAST. ADDITIONALLY, COAMPS-TC AND GEFS ENSEMBLE GUIDANCE ALSO INDICATE A HIGH PROBABILITY (50-75 PERCENT) OF RAPID INTENSIFICATION THROUGH 24H. THUS THE JTWC FORECAST LIES ABOVE THE CONSENSUS MEAN AND THE INDIVIDUAL MODEL GUIDANCE THROUGH LANDFALL, AND SLIGHTLY ABOVE THE CONSENSUS IN THE LONG-RANGE FORECAST THROUGH 120H, THOUGH THE ULTIMATE SECONDARY PEAK WILL IN VERY LARGE PART DEPEND UPON HOW MUCH OF THE CIRCULATION EMERGES BACK OVER WATER.