Tropical Cyclone 14W (Muifa) / Tropical Cyclone 15W (Merbok) / Tropical Cyclone 16W (Nanmadol) / Invest 94E
Tuesday, September 13, 2022

Current Snapshot

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By PDC’s Senior Weather
Specialist Glenn James

Tropical Cyclone 14W (Muifa)…is located approximately 214 NM south-southeast of Shanghai, China

Tropical Cyclone 15W (Merbok)…is located approximately 505 NM east of Minami Tori Shima

Tropical Cyclone 16W (Nanmadol)…is located approximately 135 NM south-southwest of Iwo To, Japan


Northeast Pacific: .

Southwest of southwestern Mexico:

>>> Shower and thunderstorm activity associated with a small area of low pressure located a few hundred miles southwest of Manzanillo, Mexico has increased some since this morning.

Although environmental conditions appear marginally favorable, some slight additional development is possible during the next day or so before it likely merges with the disturbance to its east.

* Formation chance through 48 hours…low…20 percent
* Formation chance through 5 days…low…20 percent

Near the coast of southern Mexico:

Invest 94E

>>> A trough of low pressure located along the coast of southern Mexico continues to produce disorganized cloudiness and thunderstorms.

This system is forecast to merge with the disturbance off the southwestern coast of Mexico around midweek or possibly develop as a separate system. Environmental conditions are expected to become more conducive for development by the middle part of the week.

Consequently, a tropical depression is likely to form toward the end of the week while it moves slowly westward near the coast of southern and southwestern Mexico.

* Formation chance through 48 hours…low…30 percent
* Formation chance through 5 days…high…80 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 14W (Muifa)

According to the JTWC Warning number 31, sustained winds were 85 knots with gusts to near 105 knots.

Animated enhanced infrared satellite imagery depicts a spasmodic eye with well defined, deep convective cloud lines tightly warping into the circulation center. Solid microwave imagery remains capricious, however, a microwave image shows that the eye is fragmenting and deep convection is becoming isolated to pockets around the low level center, rather than occurring throughout the system.

TY 14W continues tracking north-northwestward under the steering influence of the ridge to the northeast. By 12 hours as track speeds begin to increase past 7 knots the system will be in a marginal environment characterized by low vertical wind shear (5-10 knots) and good outflow aloft struggling to counteract falling sea surface temperature values.

By 24 hours, now just south of Shanghai, offshore sea surface temperatures values quickly overpower the other environmental factors and intensity is forecast to fall rapidly.

Just after 24 hours, as the ridge continues to force the system north-northwestward, 14W makes landfall and intensity values take a nose dive. Throughout the remaining forecast track, 14W is steadily ripped apart by southeastern China, eventually dissipating near 72 hours.

Tropical Cyclone 15W (Merbok)

According to the JTWC Warning number 14, sustained winds were 65 knots with gusts to near 80 knots.

Animated enhanced infrared satellite imagery depicts two main deep convective regions spinning cyclonically about the low level center imparting a comma like shape to the system. A microwave image shows a nearly formed eye like structure with low level cloud lines visible to the west of the low level center and deep convection visible to the east.

TS 15W is forecast to continue tracking on the western periphery of the ridge to the east. As the system rounds the ridge axis, a generally north-northwestward track will become north-northeastward. As this takes place, 15W is forecast to continue intensifying in a favorable environment characterized by warm sea surface temperatures, low vertical wind shear (10-15 knots) and improving outflow aloft.

TS Merbok will continue on its current track under the steering influence of the ridge until 12 hours. Afterward, the low- to mid-layered sub-tropical ridge to the east will assume steering and drive the cyclone more poleward.

After 36 hours, after reaching a potential peak intensity of 85 knots, sea surface temperatures values will begin to cool and vertical wind shear will increase as a mid latitude trough approaches from the west.

After 48 hours, 15W will steadily increase its interaction with this trough and progress through extra-tropical transition (ett) dramatically increasing track speeds. By 72 hours, now fully devoid of tropical characteristics, 15W will complete ett near the Aleutian island chain.

Tropical Cyclone 16W (Nanmadol)

According to the JTWC Warning number 6, sustained winds were 40 knots with gusts to near 50 knots.

Animated enhanced infrared satellite imagery depicts a broad, yet consolidating, low level circulation which appears to be improving in structure with flaring convection continuing mainly in the southern semi-circle. A partial scatterometer pass does indicate the system is starting to show a more defined core, albeit only half of the low level circulation is visible.

The environment is marginally favorable for further development with low (10-15 knot) vertical wind shear, and warm sea surface temperatures, offset by very weak radial outflow aloft. The system continues to drift northeastward under a weak steering environment.

TD 16W continues its dance between two competing steering mechanisms. There is the subtropical ridge (str) sitting to the north and the near equatorial ridge (ner) lying to the south. As in the previous prognostic reasoning, the ner is in a slightly better position and currently causing TD 16W to pursue a more northeastward track.

On or about 12 hours, TD 16W will take a turn poleward and increase in intensity to 35 knots. By 24 hours, TD 16W will head on a more west-northwestward track as the ner begins to subside and the str to the north becomes the dominant steering mechanism. At this time, the system will increase to 45 knots in intensity.

By 36 hours, the system will continue its west-northwestward track along the southwest periphery of the str and reach an intensity of 50 knots as the environment will continue to improve. By 48 hours, TD 16W will reach an intensity of 60 knots and will gradually pick up track speed.

By 72, TD 16W will reach an intensity of 75 knots, at the same time, a major shortwave trough will pass to the north and weaken the str. This will cause TD 16W to make the shift more northwestward, then finally more northerly after 96 hours where TD 16w is forecast to reach its peak intensity of 95 knots as it heads for the northern Ryukyu Islands.

By 120 hours, there will be a slight decrease in intensity to 90 knots due to land interaction with Kyushu, Japan.