Well that’s about the fastest I’ve ever seen the JTWC going from designating an invest with a low chance of formation to upgrading it to high chance and issuing a TCFA on it.
This is what has happened to Invest 97S. The JTWC had designated it around this time last night, noted it as a medium chance invest around 10-11am EST on their map they issue on their homepage to now at near 7:40 pm EST.
WTXS21 PGTW 242200
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/TROPICAL CYCLONE FORMATION ALERT (INVEST 97S)//
RMKS/
1. FORMATION OF A SIGNIFICANT TROPICAL CYCLONE IS POSSIBLE WITHIN
080 NM EITHER SIDE OF A LINE FROM 18.2S 51.3E TO 17.4S 55.8E
WITHIN THE NEXT 12 TO 24 HOURS. AVAILABLE DATA DOES NOT JUSTIFY
ISSUANCE OF NUMBERED TROPICAL CYCLONE WARNINGS AT THIS TIME.
WINDS IN THE AREA ARE ESTIMATED TO BE 28 TO 33 KNOTS. METSAT
IMAGERY AT 242200Z INDICATES THAT A CIRCULATION CENTER IS LOCATED
NEAR 18.2S 51.6E. THE SYSTEM IS MOVING SOUTHEASTWARD AT 03 KNOTS.
2. REMARKS: THE AREA OF CONVECTION (INVEST 97S) PREVIOUSLY LOCATED
NEAR 18.0S 51.5E IS NOW LOCATED NEAR 18.2S 51.6E, APPROXIMATELY
282 NM NORTHWEST OF LA REUNION. ANIMATED ENHANCED INFRARED SATELLITE
IMAGERY (EIR) DEPICTS A RAPIDLY CONSOLIDATING LOW-LEVEL CIRCULATION
CENTER (LLCC), WITH FLARING CONVECTION OVER THE CENTER. A 241725Z ASCAT
METOP-B IMAGE REVEALS 35 KNOT WINDS WITHIN THE NORTHEASTERN QUADRANT.
HOWEVER, THE 35 KNOT WIND BARS ARE FLAGGED IN THE QC VERSION OF THE
IMAGE. ENVIRONMENTAL ANALYSIS REVEALS FAVORABLE CONDITIONS FOR
DEVELOPMENT WITH LOW VERTICAL WIND SHEAR (VWS) OF 10-15 KNOTS, GOOD
EQUATORWARD UPPER-LEVEL OUTFLOW AND WARM SEA SURFACE TEMPERATURES (SST)
OF 29-30 C. BOTH DETERMINISTIC AND ENSEMBLE MODELS CONTINUE TO AGREE,
FORECASTING GRADUAL DEVELOPMENT OF INVEST 97S OVER THE NEXT 24 HOURS
WITH A GENERALLY EASTWARD TRACK. MAXIMUM SUSTAINED SURFACE WINDS ARE
ESTIMATED AT 28 TO 33 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 IS HIGH.
3. THIS ALERT WILL BE REISSUED, UPGRADED TO WARNING OR CANCELLED BY
252200Z.//
NNNN
The Satellite Fix bulletin on this has it at T#1.5, or around 30 kts.