Tropical Cyclone 18W (Noru) / Tropical Cyclone 19W (Kulap) / Invest 97W / Tropical Cyclone 02S (Ashley)
Tuesday, September 27, 2022

Current Snapshot

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By PDC’s Senior Weather
Specialist Glenn James

Tropical Cyclone 18W (Noru)…is located approximately 29 NM west of Da Nang, Vietnam – Final Warning

Tropical Cyclone 19W (Kulap)…is located approximately 339 NM east-southeast of Yokosuka, Japan

Tropical Cyclone 02S (Ashley)…is located approximately 518 NM southeast of Diego Garcia – Final Warning

 

Northeast Pacific Ocean:

South of the Southern Coast of Mexico:

An area of low pressure located south of the southern coast of Mexico is producing disorganized showers and thunderstorms.

Environmental conditions appear conducive for development, and a tropical depression is likely to form during the next few days while the system moves westward to west-northwestward off the coast of southern and southwestern Mexico.

* Formation chance through 48 hours…medium…50 percent
* Formation chance through 5 days…high…80 percent

>>> Western East Pacific:

The remnants of Newton are located nearly 1,000 miles southwest of the southern tip of the Baja California Peninsula. Bursts of shower and thunderstorm activity associated with the low has shown signs of organization today.

Some additional slight development of the system is possible for the next day or two and it could briefly become a tropical depression again while it moves generally westward over the western portion of the eastern North Pacific.

Environmental conditions are expected to become less conducive for additional development by the end of the week.

* Formation chance through 48 hours…medium…40 percent
* Formation chance through 5 days…medium…40 percent

Central Pacific:

There are no tropical cyclones nor any areas of disturbed weather under investigation by the CPHC

Northwest and Southwest Pacific Ocean, Indian Ocean, Arabian Sea:

Northwest Pacific

Tropical Cyclone 18W (Noru) – Final Warning

According to the JTWC Warning number 25, sustained winds were 80 knots with gusts to near 100 knots.

Animated enhanced infrared (eir) satellite imagery indicates that TY 18W has finally succumbed to the persistent easterly shear that has been plaguing it for some time. The satellite depiction has eroded quite dramatically over the past six hours, having gone from having a small pinhole eye to having no distinctly evident center.

While outflow remains strong and sea surface temperatures are certainly warm enough to support the system, easterly shear over 30 knots means the environment has degraded to the point of being overall unfavorable.

TY 18W is rapidly weakening at this point, having dropped from 130 knots to 105 knots in 12 hours. The system continues to track westward towards a rendezvous with the Vietnamese coastline, along the southern side of the strong steering ridge entrenched to the north.

Landfall in the vicinity of Da Nang, Vietnam, is expected within the next 12 hours, though uncertainty in the initial position means that the track speeds could be slightly faster than currently assessed, equating to a slightly earlier landfall.

The system is expected to continue to weaken in the face of persistent, strong, easterly vertical wind shear and intensity at landfall is currently expected to be around 90 knots.

Once ashore, terrain induced frictional effects combined with the continuing shear will lead to extremely fast weakening, and the system is expected to dissipate over northeast Thailand no later than 48 hours, and potentially as early as 36 hours.

Tropical Cyclone 19W (Kulap)

According to the JTWC Warning number 10, sustained winds were 60 knots with gusts to near 75 knots.

Animated enhanced infrared satellite imagery depicts a tight low level circulation center (llcc) occasionally peeking out from under cycling convection. The center was relatively devoid of deep convection, but subsequent imagery reveals another round of convection has flared up to the west of the center but it remains to be seen if this can move upshear and cover up the llcc once again.

The overall environment is marginally favorable with warm sea surface temperatures and very strong poleward outflow being offset by strong vertical wind shear and entrainment of mid-level dry air wrapping into the core from the south.

Having rounded the ridge axis a few hours ago, TS 19W has almost doubled its track speed, up to 14 knots now, as it races northeastward along the west side of the steering ridge to the east.

This trend is expected to continue, with the system steadily accelerating to the northeast as a deep shortwave trough currently across northern China begins to erode and flatten the steering ridge to the east. the biggest concern with ts 19w is not the track which is pretty firm, but the intensity and timing of the extratropical transition.

The shortwave currently over northern China is at present fairly weak, but as ts 19w moves northward and begins to pump warm air up into the higher latitudes, the downstream ridge amplifies significantly, allowing for the trough to deepen simultaneously. So much so that by 36 hours the trough has become negatively tilted and begins to pick up TS 19W as it races poleward, marking the start of extratropical transition (ett).

The system will very rapidly undergo ett (within 24 hours) and become an instant warm seclusion type extratropical low, retaining its warm core
all the way until it reaches the Bering Sea.

In the near-term the system is expected to continue to intensify as the strong shear is offset due to the in-phase track motion, allowing for the system to tap into the full effects of the very strong divergent outflow aloft.

After 24 hours, the strong baroclinic forcing associated with the negatively tilted trough will allow the system to continue to intensify even as it transitions to an extratropical low, reaching a peak of 70 knots as it completes the ett process.

>>> There’s an area of disturbed weather, being referred to as Invest 97W which is located approximately 536 NM southwest of Iwo To, Japan

Animated enhanced infrared satellite imagery show disorganized deep
convection around a broad circulation in the southwest quadrant of the
area.

Environmental analysis reveals the invest is in a marginally favorable environment for development defined by high sea surface temperatures, moderate poleward and equatorward outflow, and medium (15-25 knot) vertical wind shear.

Global models are in good agreement that Invest 97W will track northwest over the next 48-72 hours and consolidate.

Maximum sustained surface winds are estimated at 17 to 23 knots.

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

Tropical Cyclone 02S (Ashley) – Final Warning

According to the JTWC Warning number 3, sustained winds were 30 knots with gusts to near 40 knots.

Animated multi-spectral satellite imagery depicts a fully exposed low-level circulation center (llcc) with the associated convection being displaced to the southwest. This displacement is caused by strong (30-35 knot) upper-level wind flow from the north-northeast.

Tropical cyclone 02s is in a marginally unfavorable environment, characterized by strong (30-35 knot) poleward outflow aloft, offset by nominally warm seas surface temperatures, and strong (20-25 knot) vertical wind shear.

TC Ashley will continue on a west-southwestward track as it moves along the northwest sector of the ridge positioned to the southeast.

TC Ashley appears to have already peaked at 40 knots, and will now begin weakening as it transits west-southwest into a more unfavorable environment, marked by cooler sea surface temperatures, higher vertical wind shear, and drier air surrounding the llcc.

After 12 hours, TC 02S will make a southwest turn and track into even cooler waters, while the convection continually is stripped away from the center. At 24 hours the system will begin dissipating out over the southern Indian Ocean far from any landmass and complete dissipation by 36 hours if not sooner due to the harsh environment.