By PDC’s Senior Weather
Specialist Glenn James
Tropical Cyclone 10W (Ma-on)…is located approximately 169 NM northeast of Subic Bay, Philippines
Tropical Cyclone 11W (Tokage)…is located approximately 684 NM southeast of Yokosuka, Japan
Central East Pacific:
A broad area of low pressure located several hundred miles southwest of the southern tip of the Baja California peninsula is producing disorganized showers and thunderstorms.
Environmental conditions appear generally favorable for additional development, and a tropical depression could form over the next day or so as the system moves westward or west-northwestward, well offshore of the coast of Mexico. By mid-week, less favorable environmental conditions could limit further development.
* Formation chance through 48 hours…medium…40 percent
* Formation chance through 5 days…medium…40 percent
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 Ocean
Tropical Cyclone 10W (Ma-on)
According to the JTWC Warning number 7, sustained winds were 60 knots with gusts to near 75 knots.
Animated enhanced infrared satellite imagery shows that the previously exposed low level circulation center has now tucked under an area of flaring convection, which has successfully pushed back against the persistent, but weakening, northeasterly flow aloft.
The upper-level flow pattern, while still predominantly from the northeast, has become strongly divergent over top of TS 10W, relaxing the shear and allowing for development of the core of the system. The environment is generally favorable for intensification with warm sea surface temperatures, low (10-15 knot) vertical wind shear and strong poleward outflow.
TS 10W has slowed significantly over the past six hours as the steering ridge has weakened slightly, and it has run into some headwinds flowing off the coast of Luzon. The steering ridge is forecast to restrengthen and reorient to a slightly more northwest to southeast axis over the next 12 hours.
In combination with the buffer effect of the terrain features of Luzon, the system is expected to turn sharply northward, make landfall around 12 hours, and then turn onto a more northwestward track, reemerging over water off the northwest coast of Luzon by 24 hours. The system will then turn in a graceful arc towards the southeast coast of China, making landfall just south of Hong Kong just prior to 72 hours and then moving quickly inland.
While the system is experiencing a better environment currently, the short time remaining over land means it has only a small window of opportunity to intensify prior to landfall, with the current forecast calling for a peak of 50 knots by 12 hours. The system will weaken slightly as it crosses Luzon due to terrain influences, but restrengthen once in the South China Sea.
The ultimate intensity will be constrained by the fact that as the system moves across the South China Sea it will be under the influence of moderate east-northeasterly flow aloft, and while all other parameters are favorable, the persistent moderate shear will limit the peak intensity, currently forecast at 55 knots.
It remains possible however that the system could briefly reach a slightly higher intensity between 48 and 72 hours, not captured in the forecast, prior to landfall. Once ashore in China, the system will rapidly weaken to below warning criteria no later than 96 hours.
Tropical Cyclone 11W (Tokage)
According to the JTWC Warning number 4, sustained winds were 60 knots with gusts to near 75 knots.
Animated enhanced infrared (eir) satellite imagery indicates the system has taken on a shrimp-like structure, with an elongated area of deep convection to the east of the low level circulation center (llcc), which is obscured by an area of symmetrical deep convection, distinct from the eastern band. the most recent eir imagery suggest that the system is attempting to develop a banding eye feature, with some weak hot towers starting to rotate around the assessed center.
The environment is very favorable for such a high latitude system, as it lies between a weakening tropical upper tropospheric trough (tutt) to the west, and an upper-level anticyclone just to the east, which is producing strong poleward outflow over top of the system and low vertical wind shear…while sea surface temperature are quite warm as well.
TS 11W is coming together nicely under favorable environmental conditions, developing a potential banding eye and taking on the classic shrimp shape associated with developing systems. The system is expected to gradually turn to a northwestward track over the next 12 hours as the steering ridge to the east slides a bit further to the south and builds.
TS 11W will track up the western side of this ridge, and round the ridge axis by 48 hours, then accelerate northeastward along the northwestern side of the ridge through the end of the forecast period. by 60 hours the system will begin extratropical transition (ett). ETT is forecast to complete no later than 96 hours as the system rapidly moves northeast to the east of the Kuril Islands.
TS 11W has about another 12 hours under the very favorable upper-level flow pattern, before the tutt dissipates to the west and the anticyclone weakens and moves directly over the system. Once this occurs the net outflow will actually decrease, putting a cap on the intensification.
Once the system rounds the ridge axis and starts to be impacted by dramatically increased shear and quickly decreasing sea surface temperatures, it will start a rapid weakening trend, but will ultimately complete ett as a gale force low.