Current Snapshot

The Pacific Disaster Center’s (PDC Global) Monday, September 30, 2024, Tropical Cyclone Activity Report…for the Pacific Ocean, the Indian Ocean, and adjacent Seas

Current Tropical Cyclones:

Tropical Cyclone 19W (Jebi), is located about 185 NM south-southeast of Yokosuka, Japan

Tropical Cyclone 20W (Krathon), is located about 290 NM south-southwest of Taipei, Taiwan

Northeast Pacific Ocean: There are no Tropical Cyclones 

>>> Offshore of Southwestern Mexico:

An area of low pressure is expected to gradually form off the coast of southwestern Mexico during the next day or so. Environmental conditions are expected to be conducive for development after that time, and a tropical depression is expected to form by the end of the week. The disturbance is forecast to meander near or just offshore of the coast of Mexico for much of the week, and then begin moving slowly west-northwestward, parallel to the coast of Mexico by this weekend. Regardless of development, this system is expected to contribute to heavy rainfall across portions of the southwestern coast of Mexico that were already adversely affected by substantial rainfall last week, and interests there should monitor the progress of this disturbance.

* Formation chance through 48 hours…low…30 percent
* Formation chance through 7 days..high…70 percent

>>>South of the Gulf of Tehuantepec:

Invest 96E

Showers and thunderstorms associated with an area of low pressure
near the Gulf of Tehuantepec have continued to become better organized this afternoon. Although the system does not yet appear to have a well-defined surface circulation, environmental conditions are expected to be conducive for additional development, and a tropical depression is likely to form as soon as tonight or tomorrow. This system is forecast to meander for the next couple of days before drifting northward towards the southern coast of Mexico, and interests there should monitor the progress of this system. Regardless of development, heavy rain is possible along most of the coast of southern Mexico and northern Central America throughout this week.

* Formation chance through 48 hours…high…70 percent
* Formation chance through 7 days..high…70 percent

Central Pacific Ocean: There are no Tropical Cyclones.

Western Pacific, Indian Ocean, and adjacent Seas:

Tropical Cyclone 19W (Jebi)

According to the JTWC warning number 19, sustained winds were 70 knots, with gusts to 85 knots.

Animated multi-spectral satellite imagery continues to reveal improving
outflow, especially over the western semicircle, with cloud filaments along the western edge of the convection, and enhanced poleward venting into the westerlies to the north. this has allowed the system to consolidate quickly with tightly curved convective banding wrapping into a better-defined low-level circulation center (llcc).

Based on the improved environmental conditions previously discussed, TS 19W is expected to intensify to minimal typhoon strength over the next day, with a peak intensity of 65 knots near 24 hours. The track forecast is relatively straight-forward, with a northward track through 24 hours along the western periphery of the ridge.

After 24 hours, the system will begin to interact with an upper-level
shortwave trough and will commence extra-tropical transition (ett). As
the system recurves northeastward around the ridge axis, it will track
under the jet and gain frontal characteristics, completing ett by 48 hours.

Steady weakening from 24 to 48 hours is expected as the system encounters strong vertical wind shear and tracks over cooler sea surface temperature values. TS 19W will maintain a relatively compact region of gale-force winds, primarily located over the eastern semicircle, as it passes east of the Kanto Plain.

Tropical Cyclone 20W (Krathon)

According to the JTWC warning number 16, sustained winds were 130 knots, with gusts to 160 knots.

Animated multi-spectral satellite imagery depicts a well-formed, circular appearance with striated texture in the cloud tops throughout the eyewall region and a contracting eye, occluded in the center with low-based clouds. Deep convection is continuing to form in the well-wrapped spiral bands, particularly along the southern periphery and eastern eyewall.

The northwestward movement has continued to be trochoidal as the system experienced additional strengthening since the previous warning. Typhoon Krathon is generating strong radial outflow, with assistance in the equatorward direction by moderate northeasterly flow aloft over the Philippines.

Typhoon Krathon will continue drifting northwestward at a slow clip and may begin exhibiting more erratic motion as it prepares to make its expected pivot to the northeast. The onset of land interaction with southern Taiwan between 36 and 48 hours will initiate the weakening process.

It is climatologically common for typhoons in this region to display erratic and possibly a looping track motion, as well as potential for a leeside jump to occur across the mountains. Therefore, the path beyond 48 hours is plagued with large uncertainties that need to be taken into consideration and adjusted as the scenario unfolds. The bulk of the model guidance supports that an emergence of 20W will take place somewhere along the northeastern coast of Taiwan near 72 hours at a drastically weakened state.

Going forward, the system will weaken at a slow and gradual pace but largely maintain typhoon strength through the majority of the forecast period. The position of the system at 120 hours is forecast with increasing uncertainty due to ambiguity in how a westward-protruding subtropical ridge to the east situated over Japan will interact with an approaching major shortwave trough from the northwest.

>>> There’s an area of disturbed weather being referred to as Invest 91S, which is located approximately 345 NM east-southeast of Diego Garcia

Animated enhanced infrared (eir) satellite imagery depicts a broad low level circulation center (llcc) with deep flaring convection sheared off to the northwest. This llcc seems to have been present over the past 12 hours but has been slowly consolidating. A partial scatterometery pass reveals strong (25-30 knot) winds in the east-
northeastern quadrant.

Environmental analysis indicates that 91S is in a marginally favorable environment for development, due to low to moderate (15-20 knot) vertical wind shear, good poleward outflow aloft, and warm sea surface temperatures.

Numerical models are in good agreement that 91S will slowly track towards the southwest and intensify over the next 48 hours.

Maximum sustained surface winds are estimated at 23 to 28 knots.

The potential for the development of a significant tropical cyclone within the next 24 hours is low.