TC 08S(BATSIRAI) CAT 2 US: intensifying & approaching Mauritius/Réunion islands// TC 09P: slow intensification after 36h, 01/15utc

JTWC IS ISSUING 12HOURLY WARNINGS ON TC 08S(BATSIRAI) AND 6HOURLY WARNINGS ON TC 09P. 3HOURLY SATELLITE BULLETINS ARE ISSUED FOR BOTH SYSTEMS.

01/15UTC.

FORECAST REASONING. SIGNIFICANT FORECAST CHANGES: THERE ARE NO SIGNIFICANT CHANGES TO THE FORECAST FROM THE PREVIOUS WARNING. FORECAST DISCUSSION: TC 08S WILL TRACK GENERALLY WEST-SOUTHWESTWARD TO WESTWARD THROUGH 72H UNDER THE STEERING INFLUENCE OF THE SUBTROPICAL RIDGE (STR) TO THE SOUTH. TC 08S IS FORECAST TO INTENSIFY STEADILY THROUGH 72H UNDER FAVORABLE CONDITIONS AND SHOULD REACH A PEAK INTENSITY OF 110 KNOTS/CAT 3 US AT 72H ALTHOUGH A HIGHER PEAK INTENSITY IS POSSIBLE. AFTER 72H, THE STR WILL SHIFT EASTWARD AND REALIGN WITH THE APPROACH OF A MIDLATITUDE MAJOR SHORTWAVE TROUGH. THIS WILL PRODUCE A WEST-SOUTHWESTWARD TURN TOWARD A BREAK IN THE STR. TC 08S WILL MAKE LANDFALL NEAR 96H AND IS EXPECTED TO WEAKEN QUICKLY AS IT TRANSITS THE MOUNTAINOUS TERRAIN OF MADAGASCAR. HOWEVER, THE SYSTEM IS EXPECTED TO REINTENSIFY OVER THE MOZAMBIQUE CHANNEL AFTER THE FORECAST PERIOD.

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION: TC 08S HAS CONSOLIDATED OVER THE PAST 12 HOURS AND BRIEFLY FORMED A RAGGED EYE IN VISIBLE SATELLITE IMAGERY (AND ENHANCED INFRARED IMAGERY), HOWEVER, ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) NOW INDICATES THE EYE FEATURE FILLED IN OVER THE PAST TWO HOURS. A 010909Z PARTIAL AMSR2 89GHZ MICROWAVE IMAGE DEPICTS A 37KM DIAMETER MICROWAVE EYE FEATURE WHICH ALONG WITH RECENT VISIBLE SATELLITE IMAGERY SUPPORTS THE INITIAL POSITION WITH HIGH CONFIDENCE. THE INITIAL INTENSITY OF 90 KTS IS ASSESSED WITH HIGH CONFIDENCE BASED ON THE PGTW AND FMEE DVORAK ESTIMATES AND THE 010928Z SATCON ESTIMATE. THE 34-KNOT, 50-KNOT AND 64-KNOT WIND RADII WERE ADJUSTED BASED ON A DETAILED ANALYSIS OF THE 010547Z ASCAT-B IMAGE. ENVIRONMENTAL CONDITIONS REMAIN FAVORABLE WITH LOW VERTICAL WIND SHEAR AND STRONG EQUATORWARD OUTFLOW.

MODEL DISCUSSION: NUMERICAL MODEL GUIDANCE IS IN TIGHT AGREEMENT WITH A 120KM SPREAD IN SOLUTIONS AT 72H THUS THERE IS HIGH CONFIDENCE THROUGH 72H. AFTER 72H, MODEL GUIDANCE DIVERGES SLIGHTLY WITH MARKED DIFFERENCES IN TRACK SPEED THUS MEDIUM CONFIDENCE. THE ONLY EXCEPTION IS NAVGEM, THE SOLE OUTLIER, WHICH STALLS THE SYSTEM ALONG THE EAST COAST OF MADAGASCAR. COAMPS-TC INDICATES A HIGHER PEAK INTENSITY OF 115-120 KNOTS/CAT 4 US BUT THE BULK OF THE RELIABLE INTENSITY GUIDANCE INCLUDING THE JTWC INTENSITY CONSENSUS AND HWRF PEAK AROUND 100-105 KNOTS/CAT 3 US. OVERALL, THERE IS MEDIUM CONFIDENCE IN THE JTWC INTENSITY FORECAST.

FORECAST REASONING. SIGNIFICANT FORECAST CHANGES: THERE ARE NO SIGNIFICANT CHANGES TO THE FORECAST FROM THE PREVIOUS WARNING. FORECAST DISCUSSION: TC 09P IS FORECAST TO TRACK EASTWARD TO EAST-SOUTHEASTWARD UNDER THE STEERING INFLUENCE OF THE NER THROUGH 72H. TC 09P WILL MAINTAIN INTENSITY AT 35 KNOTS THROUGH 36H DUE TO DRY AIR ENTRAINMENT AS WELL AS INCREASING MID-LEVEL VERTICAL WIND SHEAR (VWS). AFTER 36H, THE SYSTEM WILL INTENSIFY SLOWLY AS VWS DECREASES, THE CORE ENVIRONMENT MOISTENS AND POLEWARD OUTFLOW IMPROVES. AFTER 72H, TC 09P WILL GRADUALLY TURN SOUTHEASTWARD ALONG THE WESTERN FLANK OF A BUILDING SUBTROPICAL RIDGE (STR) TO THE EAST. TRACK SPEEDS WILL INCREASE AFTER 72H AS THE SYSTEM TRACKS WITHIN THE ENHANCED FLOW BETWEEN THE STR AND A BROAD MIDLATITUDE TROUGH. THE SYSTEM WILL PEAK AT 55 KNOTS BY 96H THEN WEAKEN SLIGHTLY, HOWEVER, THIS PORTION OF THE INTENSITY FORECAST IS UNCERTAIN DUE TO POSSIBLE DRY AIR ENTRAINMENT AND SLIGHTLY COOLER SEA SURFACE TEMPERATURES (27-28C).

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION: ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY INDICATES AN INCREASINGLY DISORGANIZED SYSTEM WITH ERODING DEEP CONVECTION AND A WEAKLY DEFINED LOW-LEVEL CIRCULATION (LLC). A 010840Z SSMIS 91GHZ COLOR COMPOSITE MICROWAVE IMAGE REVEALED A BROAD LLC WITH A LINE OF DEEP CONVECTION TO THE NORTHWEST. TC 09P IS LOCATED JUST EAST OF AN UPPER-LEVEL POINT SOURCE WITH DIVERGENT FLOW ALONG A WEST-NORTHWEST TO EAST-SOUTHEAST AXIS, HOWEVER, CONVERGENT FLOW SOUTH OF THE SYSTEM IS RESTRICTING POLEWARD OUTFLOW. ADDITIONALLY, THERE IS SIGNIFICANT DRY AIR PRESENT OVER THE SOUTHERN PERIPHERY OF THE SYSTEM WITH MID-LEVEL DRY AIR ENTRAINMENT. SEA SURFACE TEMPERATURES (29-30C) AND VERTICAL WIND SHEAR REMAIN FAVORABLE. THE INITIAL POSITION IS PLACED WITH LOW CONFIDENCE BASED ON THE EIR AND SSMIS IMAGE. THE INITIAL INTENSITY OF 35 KTS IS ASSESSED WITH MEDIUM CONFIDENCE BASED ON THE PGTW CURRENT INTENSITY ESTIMATE OF 2.5 (35 KNOTS).

MODEL DISCUSSION: NUMERICAL MODELS ARE IN FAIR AGREEMENT WITH A 410KM SPREAD IN SOLUTIONS AT 72H. HOWEVER, THERE IS LARGE SPREAD AFTER 72H. THE BULK OF THE GUIDANCE TURNS THE SYSTEM SOUTHEASTWARD TO SOUTHWARD OVER AND JUST NORTH OF NEW CALEDONIA. THE 010600Z ECMWF (EPS) ENSEMBLE STRIKE PROBABILITY GRAPHIC INDICATES A MORE PROLONGED EAST-SOUTHEASTWARD TRACK THEN A SHARP SOUTHWARD TRACK. BASED ON THE POSITIONAL UNCERTAINTY AND SPREAD IN MODEL TRACKERS, THERE IS MEDIUM CONFIDENCE IN THE JTWC TRACK FORECAST.