Category: Posts EN

 

Typhoon Trami is beginning to move more quickly to the north and northeast today. It’ll be raking the Ryukyu Islands through tonight, but the Japanese home islands are next in the crosshairs. Heavy rains have already spread across much of Japan well ahead of the cyclone (see radar image below). Flooding, damaging winds, and a significant storm surge will accompany this ferocious storm over the weekend.

 

 

Trami is moving more quickly today. A turn to the northeast is expected later today, bringing Trami into or near southern Japan starting Sunday morning. Acceleration will continue with Trami already exiting the home islands by midday Monday. Pockets of heavy rain have broken out well ahead of the cyclone, however. Winds and waves will be on the increase through Sunday as well. Gusts along the southern coast of Japan will likely approach 85 mph (150 kph) as the cyclone passes through.

 

 

Much of the home islands will see rainfall exceeding three inches (75 mm). Central and southwest sections will see 6-12 inches (150-300 mm), with parts of eastern Kyushu and Shikoku seeing amounts exceeding 12 inches (300 mm). Significant flash flooding will be the result, especially where mountainous terrain enhances runoff. Dangerous mudslides will also occur.

 

Hurricane Rosa underwent rapid intensification early today and is now a category four cyclone. Rosa is moving slowly west and will encounter much cooler sea surface temperatures in the next few days (see map below), so weakening is likely. However, Rosa will also be speeding up and turning north, then northeast. Rosa will threaten portions of northwest Mexico and the American Southwest later this weekend into early next week.

 

 

Most of the models suggest Rosa will make an initial landfall along the northern Baja Californian coast. By then, Rosa will have weakened significantly thanks to much cooler water temperatures. However, increasing forward speed may carry it fast enough into the Desert Southwest that Rosa will retain some gusty wind potential, especially in the higher terrain near and east of the track of the circulation.

 

 

The most significant hazard, however, will likely be heavy, flooding rainfall over a region unaccustomed to the kinds of amounts in the forecast. Where the rain falls will depend on the exact track of this small but powerful storm. Most models carry the storm through central Arizona. In this corridor, expect widespread amounts of 1.5-3 inches (38-75 mm) in 12 hours or less. Localized amounts of 4-5 inches (100-125 mm) are likely. That kind of rainfall will easily overwhelm the local drainage capacity. Significant flooding will be the result!

 

 

Typhoon Trami peaked at Category Five intensity on Tuesday. Since then, Trami has been moving very slowly, allowing ocean waters to cool underneath the storm. This has cut off the supply of warm ocean moisture that typically fuels cyclones. Trami has weakened back to Category Three status, though it can still boast sustained winds to 90 knots (167 kph). Models indicate the storm could intensify a bit as it picks up speed and takes aim for Japan late this weekend into early next week.

 

 

Trami is currently drifting slowly north under the influence of weak steering winds. An approaching trough will eventually pick Trami up as the cyclone enters the East China Sea late this week. A turn to the northeast looks likely which would cause the cyclone to rake many of the Japanese home islands. The interaction with the trough would mean heavy rains breaking out in the south as early as Friday, persisting through Monday. Later next week, the typhoon will transition to be a large and powerful extratropical cyclone over the northwest Pacific.

 

 

While forward motion is so slow, conditions will not be favorable for strengthening. However, there will be a window of opportunity for some strengthening as the cyclone starts to accelerate. Trami will be a threat to produce damaging winds and a minor to moderate storm surge, especially in southern Japan. However, the more widespread threat will be flooding rainfall. Most of Japan will see amounts of at least 75-150 mm. Locations in the central and south will see totals commonly 150-300 mm, with some spots seeing totals of 400-450 mm! Serious flash flooding is likely.