From the National Weather Service…


Joaquin strengthens to a hurricane; could cause problems for Mid-Atlantic states

Hurricane Joaquin became the 2015 Atlantic season’s third hurricane Wednesday morning and hurricane watches and warnings have been issued for the Bahamas while The National Weather Service nervously watches its potential to affect the U.S. East Coast.

An Air Force Reserve Hurricane Hunter reconnaissance aircraft measured sufficiently strong flight-level winds and low surface pressure to prompt the National Hurricane Center to upgrade Joaquin Wednesday morning. The Hurricane Hunters found a 55-mile-wide eye open on its north side.

Hurricane Joaquin continues to intensify slowly, as wind shear — harmful to the intensification of tropical cyclones — lessens, and a complicated atmospheric pattern makes its future track – including any potential landfall on the U.S. East Coast – extremely difficult to forecast.

Residents along the East Coast of the U.S. should pay close attention to the forecast now through this weekend. It’s a particularly difficult forecast that hinges on the behavior of several different atmospheric features over North America and the North Atlantic Ocean.

Computer forecast models – and the meteorologists who rely on them for guidance – are grappling with a complex interaction between Joaquin, a cold front near the East Coast, the remnants of Tropical Storm Ida, a strong bubble of high pressure aloft over the North Atlantic Ocean, and a potentially strong area of low pressure aloft digging into the southeastern U.S. later this week.

Joaquin’s future depends critically on the position and relative strength of those players – not to mention its own strength. Strong wind shear had kept most of Joaquin’s thunderstorm activity (convection) south or east of its center of circulation, but that changed Tuesday afternoon and evening as thunderstorms developed closer to its circulation center.

Joaquin is expected to slowly churn toward the Bahamas Wednesday and Thursday. The extent of the effects on those islands will depend heavily on how close it gets and how much time it spends nearby before making the anticipated northward turn.

Although computer model simulations run Tuesday evening had the advantage of ingesting high-resolution real-world data from the Air Force reconnaissance flight earlier in the day, it doesn’t seem to have brought them any closer to a consensus.

The American GFS model forecast showed Joaquin making an alarming northwestward turn, slamming it right into Virginia and Maryland this weekend. Meanwhile, the European ECMWF model showed Joaquin staying well away from the U.S. East Coast, and eventually curving out into the North Atlantic well off the coasts of New England and Atlantic Canada.

It is simply too soon and the uncertainty is too high to determine any impacts from Joaquin itself for the U.S. East Coast at this time.

Regardless of the ultimate outcome of Joaquin’s path, portions of the East Coast will still see multiple impacts from the evolving large-scale weather pattern, including flooding rainfall, gusty winds, high surf, beach erosion and some coastal flooding.

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Joaquin strengthens to a hurricane; could cause problems for Mid-Atlantic states
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