Current Snapshot

The Pacific Disaster Center’s (PDC Global) Thursday, September 19, 2024, Tropical Cyclone Activity Report…for the Pacific Ocean, the Indian Ocean, and adjacent Seas

Current Tropical Cyclones:

Tropical Cyclone 15W (Pulasan), is located approximately 78 NM northwest of Shanghai, Japan

Northeast Pacific Ocean: There are no Tropical Cyclones.

>>> Central Portion of the East Pacific:

An area of low pressure could form well to the southwest of the
southwestern coast of Mexico late this weekend. Environmental conditions appear conducive for some slow development of this system thereafter as it slowly moves generally northward.

* Formation chance through 48 hours…low…near 0 percent
* Formation chance through 7 days…low…30 percent

Central Pacific Ocean: There are no Tropical Cyclones.

Western Pacific, Indian Ocean, and adjacent Seas:

Tropical Cyclone 15W (Pulasan)  

According to the JTWC Warning number 14, sustained winds are 30 knots…with gusts to near 40 knots

Earlier today, TS 15W exhibited a brief, misleading history of a tc-like appearance on animated multi-spectral satellite imagery due to flaring convection and dispersed outflow poleward and to the east. However, the system continues to predominantly meet the characteristics of a monsoon depression, which include the following attributes. animated enhanced infrared (eir) and microwave satellite

Imagery shows a loosely organized band of weak convective elements on the eastern semicircle and a cluster of pulsing convection over a sharp wave that extends northeastward from the low pressure center.
Scatterometry shows a low-level wind distribution of light winds in the core and a radius of maximum winds displaced greater than 150 NM from the pressure center.

Due to the expansive cyclonic circulation, the system’s center position was relocated further south in the axis of sharpest troughing. This sharp wave extends between the pressure center and a region of gradient-driven wind maxima approximately 150 NM to the northeast. Additionally, IR imagery reveals a hallmark absence of a cloud system center over the system’s center position. most notably, because there is no evidence of a closed surface circulation, the system is difficult to track and the current position is placed with significant uncertainties and low confidence.

The system is expected to make landfall in coastal China near Shanghai, while the ill-defined patch of wind maxima will remain just offshore. The weak TD will slow drastically or stall over land until getting picked up by an approaching trough. The winds associated with the system will decrease slightly in intensity while the system is over land at 24 hours, and subsequently return to a similar magnitude (35 knots) due to the tight pressure gradient between the trough and the sharp subtropical steering ridge to the east.

The approaching trough is associated with a combined 150-knot jet stream maximum and a tight thermal gradient that will introduce a baroclinic zone between 24 and 36 hours. As the trough picks up the system remnants, it will re-emerge and deepen over the East China Sea as a developing stable wave, to include frontogenesis.

As the pressure center tracks quickly eastward, extratropical transition will occur. The developing stable wave will track through the Korea Strait, possibly making landfall near Japan. The location of the jet stream over the Republic of Korea will prevent the system from venturing north; if by slim chance it does, it can only do so as an extratropical low. Extratropical transition will become complete by 72 hours.

>>> There’s an area of disturbed weather, being referred to as Invest 90W, which is located approximately 368 NM east-southeast of Taipei, Taiwan

Animated visible satellite imagery depicts exposed low level cloud lines wrapping into a defined circulation center. Convection is flaring in the southern quadrant with anvils sheared to the south. A partial scatterometry pass shows the system is forming adjacent to an extensive belt of 20-30 knot southeasterly winds to the east of the circulation.

Environmental conditions are marginally favorable with moderate equatorward outflow aloft, moderate to high (20-25 knots) vertical wind shear and warm sea surface temperatures creating a conducive area for further development moving forward.

Deterministic and probabilistic models depict a deepening system forming beside the wide swath of vigorous low-level flow and heading generally northwestward. Global models indicate slow development; however, they do indicate a possibility for the stronger winds to the east to wrap around the circulation.

Maximum sustained surface winds are estimated at 20 to 25 knots.

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