Western Pacific: 19W(CHANTHU) monitored for the past 12 days and still there//Atlantic: Tropical Cyclone Formation Alert issued again for 96L,17/09utc

17/00UTC.

TS 19W(CHANTHU). WARNING 45 ISSUED AT 17/09UTC.SIGNIFICANT FORECAST CHANGES: THERE ARE NO SIGNIFICANT CHANGES TO THE FORECAST FROM THE PREVIOUS WARNING. FORECAST DISCUSSION: TS 19W HAS ROUNDED THE RIDGE AXIS AND IS NOW ACCELERATING TOWARDS THE EAST-NORTHEAST. THE SYSTEM HAS SKIRTED THE NORTHWESTERN TIP OF KYUSHU AND IS RAPIDLY MOVING TOWARDS A LANDFALL IN THE VICINITY OF FUKUOKA IN THE NEXT COUPLE OF HOURS. IT IS FORECAST TO CONTINUE MOVING GENERALLY EASTWARD, THROUGH THE INLAND SEA AND EMERGE BACK OVER THE PACIFIC JUST AFTER 24H. AS THE SYSTEM MOVES THROUGH THE INLAND SEA, INTERACTION WITH THE COMPLEX AND RUGGED TERRAIN WILL, IN CONJUNCTION WITH STEADILY INCREASING WESTERLY SHEAR, LEAD TO STEADY WEAKENING THROUGH THE FORECAST PERIOD. ANALYSIS OF 500MB DATA INDICATES A SMALL SHORT-WAVE TROUGH JUST WEST OF THE SYSTEM, WHICH IS EXPECTED TO MOVE IN PHASE WITH TS 19W OVER THE NEXT 24 HOURS, FACILITATING THE START OF EXTRA-TROPICAL TRANSITION (ETT). HOWEVER, BY 36H THIS SHORTWAVE TROUGH WILL OUTPACE TS 19W, PUTTING IT UNDER CONVERGENT FLOW ALOFT LEADING TO FURTHER WEAKENING AFTER 48H AS THE SYSTEM MOVES BACK OVER WATER. GLOBAL MODELS CONTINUE TO SHOW THE DEVELOPMENT OF A SECONDARY LOW PRESSURE AREA, A POSSIBLE TRIPLE POINT LOW, TO THE WEST OF HONSHU, WHICH THEN MOVES NORTHEAST IN PHASE WITH THE SHORTWAVE TROUGH MENTIONED EARLIER. THIS LOW THEN BECOMES THE DOMINATE EXTRA-TROPICAL SYSTEM, DEVELOPING STRONG FRONTAL FEATURES WHICH WILL EXTEND SOUTHWESTWARD TO THE VICINITY OF TS 19W, WHICH WILL MERGE WITH THE FRONT BOUNDARY SOUTH OF TOKYO. STRONG RIDGING BUILDING INTO FROM THE NORTHWEST BEHIND THE PRIMARY LOW WILL BLOCK FURTHER NORTHEAST MOVEMENT OF TS 19W AND THE SYSTEM IS EXPECTED TO SLOW AND TURN SOUTH TO THE SOUTHEAST OF TOKYO AFTER 48H, ALONG THE TAIL END OF THE DECAYING FRONTAL BOUNDARY. TS 19W WILL COMPLETE ETT BY 36H AND WILL REMAIN A WEAK EXTRA-TROPICAL LOW THROUGH 72H, WHILE SLOWLY DISSIPATING.

TS 19W(CHANTHU).SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION: ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) AND ANIMATED JMA RADAR DATA INDICATE THE SYSTEM WAS CROSSING JUST OFFSHORE OF IKITSUKI-SHIMA AT THE 0600Z HOUR HAD NOT YET MADE LANDFALL. ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTED A PARTIALLY EXPOSED LOW LEVEL CIRCULATION CENTER (LLCC) WITH SHEARED, FLARING CONVECTION TO THE NORTHEAST. THE INITIAL POSITION IS PLACED WITH HIGH CONFIDENCE BASED ON THE PARTIALLY EXPOSED LLCC AND THE RADAR DATA. THE INITIAL INTENSITY HAS BEEN LOWERED TO 40 KNOTS WITH HIGH CONFIDENCE BASED ON A COMBINATION OF FACTORS. AGENCY CURRENT INTENSITY ESTIMATES RANGE BETWEEN T2.5-T3.0 (35-45 KNOTS), WHILE ADT WAS A PALTRY 32 KNOTS AND SATCON WAS 39 KNOTS, PLACING THE INITIAL INTENSITY SQUARELY IN THE AVERAGE OF THESE DATA. ADDITIONALLY, SURFACE OBSERVATIONS FROM THE REGION AT 0600Z SHOWED PRESSURES BETWEEN 994-997MB, WHICH WOULD SUPPORT A 40 KNOT SYSTEM. LASTLY, WIND READINGS FROM NAGASAKI WERE 41 KNOTS SUSTAINED WITH GUSTS TO 60 KNOTS, 29 KNOTS GUSTING TO 40 KNOTS AT SAGA AND 28 KNOTS GUSTING TO 40 KNOTS AT SASEBO. THE SYSTEM IS MOVING THROUGH AN INCREASINGLY HOSTILE ENVIRONMENT, WITH MODERATE AND INCREASING WESTERLY SHEAR OFFSETTING STRONG POLEWARD OUTFLOW.

TS 19W(CHANTHU). MODEL DISCUSSION: WITH THE EXCEPTION OF GALWEM, WHICH APPARENTLY JUMPS CIRCULATIONS TO THE EXTRA-TROPICAL SYSTEM WEST OF HONSHU AND TRACKS RAPIDLY NORTHEAST, TRACK GUIDANCE IS IN FAIRLY GOOD AGREEMENT WITH AN 160KM SPREAD AT 24H. AFTER 24H, AS THE SYSTEM BECOMES INCREASINGLY BROAD AND DISORGANIZED, THE GUIDANCE DIVERGES, WITH ALL TRACKERS WITH THE EXCEPTION OF THE ECMWF ENSEMBLE, AGREEING ON A SLOW TRACK PASSING SOUTH OF TOKYO FOLLOWED BY A TURN SOUTHWARD AFTER 48H. THE JTWC FORECAST LIES ON THE NORTH SIDE OF THE GUIDANCE ENVELOPE THROUGH 48H, THEN JUST EAST OF THE CONSENSUS MEAN THROUGH 72H. OVERALL CONFIDENCE IS MEDIUM, WITH SIGNIFICANT UNCERTAINTY AFTER 36H. THE JTWC INTENSITY FORECAST IS SLIGHTLY HIGHER THAN THE CONSENSUS MEAN WITH MEDIUM CONFIDENCE.

17/00UTC.

ATLANTIC. INVEST 96L. TROPICAL CYCLONE FORMATION ALERT ISSUED AT 16/14UTC.

INVEST 96L. TRACK AND INTENSITY GUIDANCE.

17/10UTC.