North Indian: 2 Tropical Cyclones in August! TC 04B making landfall// Invest 93W// Invest 99L, 19/03utc

JTWC IS ISSUING 6HOURLY WARNINGS AND 3HOURLY SATELLITE BULLETINS ON TC 04B

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION: ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS A MASS OF BUILDING CONVECTION OVER THE SOUTHERN PERIPHERY OF AN ASSESSED LOW LEVEL CIRCULATION (LLC) TRACKING WEST-NORTHWEST OVER THE NORTHERN BAY OF BENGAL. AN 182313Z 91 GHZ SSMIS PASS SHOWS FRAGMENTED BANDING IN THE WESTERN AND SOUTHERN QUADRANTS WRAPPING INTO THE CENTER OF THE LLC. THIS PASS ALSO INDICATES A MAJORITY OF THE CONVECTIVE ACTIVITY TO BE IN THE SOUTHERN PERIPHERY AS WELL AS IN THE OUTER BAND THAT STRETCHES NORTHWEST TO NORTHEAST OF KOLKATA, INDIA. ENVIRONMENTAL ANALYSIS INDICATES TC 04B IS IN A MARGINALLY FAVORABLE AREA FOR FURTHER DEVELOPMENT WITH SPLIT WESTWARD AND EQUATORWARD UPPER LEVEL OUTFLOW, A HIGH MAGNITUDE 850 MB SIGNATURE, AND WARM (29-30 C) SEA SURFACE TEMPERATURES, OFFSET BY MODERATE (15-20 KTS) VERTICAL WIND SHEAR (VWS). THE INITIAL POSITION IS PLACED WITH MEDIUM CONFIDENCE BASED ON MULTIPLE AGENCY FIXES, PARTIAL RADAR IMAGERY FROM KOLKATA AND THE AFOREMENTIONED EIR DATA. THE INITIAL INTENSITY OF 40 KTS IS ASSESSED WITH MEDIUM CONFIDENCE SET LOWER THAN THE PGTW DVORAK ESTIMATE AND HIGHER THAN AUTOMATED AND OTHER AGENCY DVORAKS.

FORECAST REASONING. SIGNIFICANT FORECAST CHANGES: THERE ARE NO SIGNIFICANT CHANGES TO THE FORECAST FROM THE PREVIOUS WARNING. FORECAST DISCUSSION: TC 04B CONTINUES ON A DIRECT PATH TO MAKE LANDFALL ALONG THE COAST OF NORTHEAST INDIA APPROXIMATELY 75 NM SOUTHWEST OF KOLKATA. THE INTENSITY WILL STEADILY INCREASE TO 45 KNOTS BY TAU 12 DURING LANDFALL AS THE VERTICAL WIND SHEAR IS EXPECTED TO CONTINUE TO DECREASE DUE TO A BREAK IN THE UPPER LEVEL WINDS OVER THE NEXT 18 HOURS. BY TAU 24 TC 04B WILL DECREASE IN INTENSITY TO 35 KNOTS AND BEGIN DISSIPATION DUE TO LAND INTERACTION. BY TAU 36 THE SYSTEM WILL BE DISSIPATED WITH THE INTENSITY FALLING TO 30 KNOTS.

MODEL DISCUSSION: THE JTWC TRACK CONSENSUS ENVELOPE CONTINUES TO BE RELATIVELY TIGHT AIMING NORTHWESTWARD WITH NAVGEM BEING THE OUTLIER WITH A JOG WESTWARD IMMEDIATELY OUT TO TAU 12, THEN EASING INTO A MORE WEST-NORTHWESTWARD DIRECTION AFTERWARDS. DUE TO THIS OUTLIER THE JTWC FORECAST TRACK IS SET SLIGHTLY TO THE RIGHT OF TRACK WITH HIGH CONFIDENCE. INTENSITY GUIDANCE IS IN BETTER AGREEMENT THAN THE PREVIOUS MODEL RUN WITH A 5-10 KNOT SPREAD AT TAU 12. THIS IMPROVED AGREEMENT COUPLED WITH THE IMPROVING ENVIRONMENT OVER THE NEXT 18 HOURS LENDS MEDIUM CONFIDENCE IN THE JTWC INTENSITY FORECAST WHICH IS SET SLIGHTLY HIGHER THAN CONSENSUS.

THE AREA OF CONVECTION (INVEST 93W) PREVIOUSLY LOCATED NEAR 15.3N 133.9E IS NOW LOCATED NEAR 17.6N 131.4E, APPROXIMATELY 709 NM SOUTHEAST OF TAIPEI, TAIWAN. A 190109Z ASCAT-C PARTIAL PASS DEPICTS A TROPICAL WAVE FEATURE WITH A LARGE SWATH OF MOSTLY 15KT CONVERGENT SOUTHERLY WINDS WITH A FEW 30KT WINDS ALONG THE EASTERN SEMICIRCLE. ANIMATED ENHANCED INFRARED SATELLITE IMAGERY DEPICTS SCATTERED POCKETS OF DEEP CONVECTION ASSOCIATED WITH THE STRONG LOW LEVEL CONVERGENT FLOW. A 190317Z GMI 89GHZ PARTIAL PASS INDICATES DISORGANIZED DEEP CONVECTION WITH NO EVIDENCE OF A DEFINED LOW LEVEL CIRCULATION CENTER. ENVIRONMENTAL ANALYSIS REVEALS MARGINALLY FAVORABLE CONDITIONS FOR DEVELOPMENT DEFINED BY WEAK POLEWARD AND MODERATE EQUATORWARD OUTFLOW ALOFT, LOW (5-10KT) VWS AND VERY WARM (29-30C) SST VALUES. GLOBAL MODELS HAVE BACKED OFF ON THE INTENSIFICATION OF 93W BUT GENERALLY AGREE THAT THE SYSTEM WILL SLOWLY MEANDER ALONG A WEST-NORTHWESTWARD TRACK TOWARD TAIWAN. MAXIMUM SUSTAINED SURFACE WINDS ARE ESTIMATED AT 10 TO 15 KNOTS. MINIMUM SEA LEVEL PRESSURE IS ESTIMATED TO BE NEAR 1007 MB. THE POTENTIAL FOR THE DEVELOPMENT OF A SIGNIFICANT TROPICAL CYCLONE WITHIN THE NEXT 24 HOURS REMAINS LOW.

GLOBAL MODELS HAVE BACKED OFF ON THE INTENSIFICATION OF 93W BUT GENERALLY AGREE THAT THE SYSTEM WILL SLOWLY MEANDER ALONG A WEST-NORTHWESTWARD TRACK TOWARD TAIWAN.