WPAC: RAGASA - Typhoon

[cycloneye]

Is organizing at a steady rate.

[cycloneye]

FORECAST DISCUSSION: 24W IS FORECAST TO TRACK RATHER SLOWLY
NORTHWESTWARD OVER THE NEXT 48 HOURS AS THE SUBTROPICAL RIDGE TO
THE NORTH CONTINUES TO BUILD. NEAR TAU 72, THE RIDGE WILL HAVE
BUILT IN AND WILL HAVE MORE INFLUENCE ON STEERING THE VORTEX. 24W
WILL THEN INCREASE TRACK SPEEDS AS IT PASSES THROUGH THE LUZON
STRAIT WITH A MORE WEST-NORTHWESTWARD TRAJECTORY. THIS MOTION WILL
THEN PERSIST THROUGH THE REMAINDER OF THE FORECAST PERIOD AS THE
SYSTEM APPROACHES THE SOUTHERN COAST OF CHINA. REGARDING INTENSITY,
24W IS FORECAST TO RAPIDLY INTENSIFY OVER THE NEXT 48 HOURS TO
AROUND 105 KTS. ENVIRONMENTAL CONDITIONS WILL BE NEARLY PERFECT
FOR RAPID DEVELOPMENT AS THE SYSTEM TAPS INTO AN IMPROVED POLEWARD
OUTFLOW CHANNEL OVER THE NEXT 24 HOURS. A PEAK INTENSITY OF AROUND
120 KTS IS FORECAST TO OCCUR NEAR TAU 72, NORTH OF LUZON. EASTERLY
VERTICAL WIND SHEAR IS EXPECTED TO INCREASE TO 15-20 KTS AT TAU 96
AND ONWARD, CAUSING 24 TO SLIGHTLY WEAKEN AS IT HEADS FOR THE
SOUTHERN COAST OF CHINA.

MODEL DISCUSSION: NUMERICAL MODEL TRACK GUIDANCE CONTINUES TO BE IN
GOOD AGREEMENT WITH A 95 NM CROSS-TRACK SPREAD AT TAU 72 WHICH
OPENS UP TO 165 NM AT TAU 120. GFS HAS BECOME THE NORTHERNMOST
MEMBER THROUGH THE LUZON STRAIT WHILE ECMWF TRACKS THE SYSTEM
CLOSER TO NORTHERN LUZON. THE JTWC TRACK FORECAST IS PLACED CLOSE
TO THE MULTI-MODEL CONSENSUS, HEDGED SLIGHTLY CLOSER TO ECMWF, WITH
HIGH CONFIDENCE THROUGH TAU 72 AND MEDIUM CONFIDENCE THEREAFTER.
NEARLY ALL RAPID INTENSIFICATION (RI) AIDS ARE TRIGGERING THIS
MODEL RUN. MESOSCALE MODELS ARE IN GOOD AGREEMENT IN TERMS OF THE
PEAK INTENSITY OF 24W WITH HAFS-A, HWRF, AND COAMPS-TC ALL RANGING
FROM 115 TO 125 KTSAT TAU 72. GUIDANCE ALSO AGREES ON WEAKENING
AFTER TAU 72. OF NOTE, HWRF TRACKS THE SYSTEM FURTHER NORTH,
CLIPPING SOUTHERN TAIWAN, AND THEREFORE WEAKENS THE SYSTEM MUCH
MORE QUICKLY THAN HAFS-A OR COAMPS-TC. THE JTWC INTENSITY FORECAST
IS PLACED CLOSE TO THE MULTI-MODEL CONSENSUS THROUGH TAU 48, AND
THEN CLOSE TO HAFS-A FOR THE REMAINDER OF THE FORECAST PERIOD WITH
OVERALL LOW CONFIDENCE.

[Travorum]

A solid band wrapping shown on a microwave pass from 6 hours ago

[cycloneye]

JMA up to Severe Tropical Storm:

T2518(Ragasa)
Issued at 2025/09/19 18:45 UTC
Analysis at 09/19 18 UTC
Grade STS
Scale -
Intensity -
Center position N16°35′ (16.6°)
E129°55′ (129.9°)
Direction and speed of movement WNW 15 km/h (7 kt)
Central pressure 990 hPa
Maximum sustained wind speed near center 30 m/s (55 kt)
Maximum wind gust speed 40 m/s (80 kt)
Radius of 50-kt wind area 55 km (30 NM)
Radius of 30-kt wind area 390 km (210 NM)

[cycloneye]

 https://x.com/Sausius_wx/status/1969111341370638582

[cycloneye]

A. 24W (RAGASA)

B. 19/1730Z

C. 16.3N

D. 129.6E

E. THREE/HIMAWARI-9

F. T3.5/3.5

G. IR/EIR/SWIR/PRXY

H. REMARKS...8/10 BANDING ON A LOG10 SPIRAL RESULTS IN A DT OF 3.5. THE
MET EQUALS 3.5 BASED ON A RAPIDLY DEVELOPING 24-HOUR TREND AND THE PT
ALSO EQUALS 3.5. THE FT IS BASED ON THE DT.

I. ADDL POSITIONS

NIL


...LINER

[Hayabusa]

JMA up to Severe Tropical Storm:

T2518(Ragasa)
Issued at 2025/09/19 18:45 UTC
Analysis at 09/19 18 UTC
Grade STS
Scale -
Intensity -
Center position N16°35′ (16.6°)
E129°55′ (129.9°)
Direction and speed of movement WNW 15 km/h (7 kt)
Central pressure 990 hPa
Maximum sustained wind speed near center 30 m/s (55 kt)
Maximum wind gust speed 40 m/s (80 kt)
Radius of 50-kt wind area 55 km (30 NM)
Radius of 30-kt wind area 390 km (210 NM)

Actually JMA upgraded it to STS at 1500z (intermediate time)

WTPQ51 ‎RJTD ‎191500
RSMC ‎TROPICAL ‎CYCLONE ‎ADVISORY
NAME ‎ ‎STS ‎2518 ‎RAGASA ‎(2518) ‎UPGRADED ‎FROM ‎TS
ANALYSIS
PSTN ‎ ‎191500UTC ‎16.5N ‎130.0E ‎FAIR
MOVE ‎ ‎W ‎08KT
PRES ‎ ‎992HPA
MXWD ‎ ‎050KT
GUST ‎ ‎070KT

[Travorum]

Here's 37 GHz imagery throughout the past day showing Ragasa quickly organizing over the past 12 hours, from about 12z to 17z to 21z:



The banding has very quickly wrapped around and the beginnings of a cyan ring have emerged, all signs that Ragasa is developing a structure primed for rapid intensification.

Additionally, after the latest 21z microwave pass, three hot towers have shot up around the center of the storm:

[mrbagyo]

This should have been a typhoon as early as 18z

[mrbagyo]

saved loop

[sasha_B]

2330Z satellite bulletin from JTWC:

H. REMARKS: 40A/PBO SBC/ANMTN. CNVCTN WRAPS 1.10 ON LOG10 SPIRAL
YIELDING A DT OF 4.0. MET YIELDS 3.5. PT YIELDS 4.0. DBO DT.

[cycloneye]

 https://x.com/RyanMaue/status/1969200276453441724

[sasha_B]

Unless there's an override, it looks like the JTWC doesn't note any intensification. Likewise the JMA is sticking with 55 kts as of 0100z.

Edit: This is in fact now a 65 kt typhoon.

24W RAGASA 250920 0000 16.3N 129.6E WPAC 65 985

[dexterlabio]

It is a very broad circulation but it's building a tiny, compact core.

[cycloneye]

FORECAST DISCUSSION: TY 24W IS FORECASTED TO TRACK TO THE NORTHWEST
THROUGH TAU 48, ALONG THE SOUTHWESTERN FLANK OF THE SUBTROPICAL
STEERING RIDGE (STR) DIRECTLY TO THE NORTH. AFTER TAU 48, THE TRACK
BECOMES MORE WESTWARD AS A COMPETING EQUATORIAL RIDGE TO THE
SOUTHWEST BEGINS WEAKENING AND RETREATING WESTWARD. AS THE
EQUATORIAL RIDGE RETREATS OVER MALAYSIA, THE TRACK FOR TY 24W IS
FORECASTED TO BECOME WEST-NORTHWEST THROUGH THE LUZON STRAIT AND
INTO TAU 96 JUST SOUTH OF COASTAL SOUTHERN CHINA. BETWEEN TAU 96
AND TAU 120, THE EXPECTED TRACK BECOMES WESTWARD AS AN EXTENSION OF
THE SUBTROPICAL RIDGE TO THE EAST BEGINS TO BUILD WESTWARD, JUST
NORTH OF TY 24W. WITH REGARD TO INTENSITY, THE CONTINUED HIGHLY
FAVORABLE ENVIRONMENT IS FORECASTED TO SUPPORT FURTHER
INTENSIFICATION TO 120 KTS BY TAU 72, WITH FAVORABLE SEA SURFACE
TEMPERATURES, LOW VWS, AND STRONG OUTFLOW ALOFT. FOLLOWING TAU 72,
VWS IS FORECASTED TO INCREASE ABOVE 15 KTS WITH DRY AIR BEGINNING
TO WRAP CYCLONICALLY AROUND THE WESTERN PERIPHERY OF THE SYSTEM.
DURING THIS PERIOD, PERSISTENT LAND INTERACTION WITH SOUTHERN
COASTAL CHINA ALONG THE NORTHERN SEMICIRCLE OF TY 24W WILL BEGIN TO
WEAKEN SURFACE INTENSITIES INTO THE END OF THE FORECAST PERIOD.

MODEL DISCUSSION: NUMERICAL MODEL PREDICTION TRACK GUIDANCE IS IN
GOOD AGREEMENT THROUGHOUT THE FORECAST PERIOD, WITH A CROSS-TRACK
SPREAD OF 108 NM AT TAU 72, INCREASING TO 178 NM BY TAU 120.
BETWEEN TAU 96 AND TAU 120, ALL JTWC CONSENSUS MEMBERS ILLUSTRATE
TY 24W TO TRACK WESTWARD, RIGHT ALONG COASTAL SOUTHERN CHINA, NORTH
OF HAINAN. THE JTWC FORECAST IS ALIGNED CLOSELY WITH THE
MULTI-MODEL CONSENSUS THROUGH TAU 120, LENDING HIGH CONFIDENCE TO
THE JTWC TRACK FORECAST. WITH REGARD TO INTENSITY, THE JTWC
INTENSITY FORECAST IS ASSESSED WITH MEDIUM CONFIDENCE THROUGH TAU
120 AND PLACED JUST HIGHER THAN THE JTWC MULTI-MODEL INTENSITY
CONSENSUS DUE TO THE FORECASTED QUICK INTENSIFICATION INTO TAU 72.

[cycloneye]

Josh once again going for another chase.

 https://x.com/iCyclone/status/1969168718509862960

[cycloneye]

 https://x.com/dost_pagasa/status/1969237044644687922

[mrbagyo]

[cycloneye]

Finnally JMA upgrades.

T2518(Ragasa)
Issued at 2025/09/20 06:45 UTC
Analysis at 09/20 06 UTC
Grade TY
Scale -
Intensity -
Center position N16°55′ (16.9°)
E129°00′ (129.0°)
Direction and speed of movement WNW 10 km/h (6 kt)
Central pressure 975 hPa
Maximum sustained wind speed near center 35 m/s (65 kt)
Maximum wind gust speed 50 m/s (95 kt)
Radius of 50-kt wind area 75 km (40 NM)
Radius of 30-kt wind area SE560 km (300 NM)
NW390 km (210 NM)

[Hayabusa]

ADT raw rising

2025SEP20 060000 3.5 988.7 55.0 3.5 3.9 5.8 0.5T/hour OFF OFF OFF OFF -23.07 -71.16 EYE -99 IR 10.3 16.70 -129.05 FCST HIM-9 23.7
2025SEP20 063000 3.7 986.3 59.0 3.7 4.0 5.9 0.5T/hour OFF OFF OFF OFF -8.60 -70.64 EYE -99 IR 10.3 16.74 -129.01 FCST HIM-9 23.8
2025SEP20 071000 3.7 984.9 59.0 3.7 4.0 6.2 0.5T/hour OFF OFF OFF OFF 2.20 -71.65 EYE -99 IR 10.3 16.78 -128.96 FCST HIM-9 23.8
2025SEP20 073000 4.0 982.5 65.0 4.0 5.2 6.1 1.7T/6hr OFF OFF OFF OFF 5.00 -70.36 EYE 16 IR 10.3 16.81 -128.94 FCST HIM-9 23.9
2025SEP20 081000 4.2 978.1 69.8 4.2 5.1 6.0 1.7T/6hr OFF OFF OFF OFF -4.11 -70.23 EYE 16 IR 10.3 16.84 -128.88 FCST HIM-9 24.