Super Typhoon Vongfong rapidly intensifies overnight - equivalent to a Category 4 hurricane and heading for Japan

Super Typhoon Vongfong, as feared, intensified rapidly overnight Monday into Tuesday, U.S. time. The satellite image above with the classic distinct eye says it all.

As of midnight local time Wednesday, the eye of Vongfong was about 750 miles southeast of Kadena Air Base on Okinawa, moving west at 10-15 mph.

Maximum sustained winds had increased to an estimated 155 mph, the equivalent of a Category 4 hurricane, according to the U.S. military's Joint Typhoon Warning Center.

Vongfong became the fifth super typhoon (150 mph max sustained winds or higher) of 2014. According to the Japan Meteorological Agency, Vongfong has now surpassed Genevieve for the most intense western Pacific typhoon of 2014 by estimated central pressure (905 millibars).

With low vertical wind shear (change in wind speed and/or direction with height), impressive outflow (winds in the upper levels spreading apart from the center, favoring upward motion and thunderstorms) and warm western Pacific water, Vongfong may intensify further over the next day or so, possibly reaching Category 5 equivalent status (157 mph or higher max sustained winds).

Intense tropical cyclones undergo eyewall replacement cycles (ERC), during which the old inner eyewall is replaced by a contracting outer eyewall. During that time, the intensity backs off a bit. The timing of these ERCs cannot be forecasted using present technology.

Similar to what happened with Typhoon Phanfone, Vongfong will turn north in the next day or so, as it rounds the western edge of the subtropical steering high mentioned above.

However, in contrast to the scenario with Phanfone, a second, temporary blocking high pressure system aloft may deflect Vongfong slightly to the west Friday through Sunday.

This is a disconcerting possibility, as it could bring the core of Vongfong's strongest winds much closer to the Ryuku Islands this weekend than otherwise would happen. It should be noted Vongfong is expected to weaken once it begins moving north this week, but should still be a formidable typhoon as it draws close to Japan this weekend into early next week.

That temporary upper-level ridge will eventually be replaced by a dip in the jet stream, or trough, that will finally grab hold of Vongfong and accelerate it toward the east-northeast, similar to what happened with Typhoon Phanfone.

It is still too soon to be certain regarding specific impacts to Japan from Vongfong.

However, at the present time it appears Vongfong will end up tracking far enough west and north to at least bring some high winds, heavy rain and storm surge flooding once again to Okinawa, Kyushu, Shikoku, and at least central and eastern Honshu Saturday through Tuesday.

Those with interests or travel plans in these areas should monitor closely the progress of Vongfong on weather.com and The Weather Channel.

Guam Impact

Based on data from the National Weather Service Doppler radar on Guam, the eye of Typhoon Vongfong passed near or over Rota Island, which is about 45 miles north-northeast of Guam, between 3 and 4 a.m. local time Monday (1 and 2 p.m. EDT Sunday).

In a series of statements issued Sunday, the NWS office repeatedly warned that "devastating damage [was] expected" on the island of Rota, which lies in the Northern Mariana Islands, a U.S. commonwealth.

The bulletin, eerily reminiscent of one issued by the NWS New Orleans office before Hurricane Katrina in August 2005, included these ominous descriptions of potential destruction from winds that were forecast to gust as high as 140 mph:

"Collapse of some residential structures will put lives at risk. Airborne debris will cause extensive damage. Persons or animals struck by the wind blown debris will be injured or killed. Electricity and water will be unavailable for days and perhaps weeks after the storm passes. Most trees will be snapped or uprooted. Fallen trees may cut off residential areas for days to weeks."

The bulletin said the islands of Tinian and Saipan to the north, as well as Guam to the south, could expect damage of a less extreme nature.

Fortunately, damage was much less severe than expected on Rota. While 70 percent of the island lost power, there had been no reported injuries.

Guam experienced sustained tropical storm force wind with typhoon strength gusts at times. Flash flood warnings were issued for Guam due to heavy rain.

Vongfong was first designated a tropical depression early Thursday, local time, and steadily gained strength as it approached Guam and the Northern Mariana Islands. According to the U.S. military's Joint Typhoon Warning Center, Vongfong strengthened into a typhoon Saturday.