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[Ripclawe]

http://weblogs.sun-sentinel.com/news/weather/hurricane/blog/

Updated at 2 p.m.

As we're already reporting, Hanna intensified into a hurricane this afternoon, about three days sooner than expected.

That makes it the fourth hurricane of the season, behind Bertha, Dolly and Gustav.

Because the system is expected to draw uncomfortably close to the South Florida coastline Wednesday and Thursday, this region is already in the three-day cone of error.

Which means we could see a hurricane watch or warning issued for the southeast coast by Tuesday.

Meanwhile, a new tropical depression formed in the Central Atlantic today, and it is initially forecast to aim generally toward Florida. It's also predicted to become a hurricane.

At 11 a.m. today, TD-9, which is expected to become Tropical Storm Ike in short order, was 1,470 miles east of the Leeward Islands. It was moving west at 16 mph with sustained winds of 35 mph.

It formed even as the future meanderings of Hurricane Hanna remain unresolved, keeping the entire Florida coastline on its toes.

For now, the National Hurricane Center continues to predict Hanna will turn north before reaching the state's shoreline and head for Georgia or the Carolinas.

However, its track was shifted slightly to the west, putting its core near Grand Bahama Island on Thursday.

In other words, it would be about 150 miles due west of West Palm Beach as it passes north of our position.

That would be close enough that South Florida should feel some of its winds starting as early as Tuesday and continuing through the rest of the week.

How much wind depends on how large it grows over the next couple of days, said Kim Brabander, meteorologist with the National Weather Service in Miami.

“The big thing would be swells coming to the Palm Beach and Broward coasts and the high risk of rip currents,” he said.

If Hanna remains on its current projected path, most of its severe weather would be on its east side over the ocean. South Florida would be on its tamer west side.

That might be a big if at this point. Because its forward progress has slowed down, that adds to the uncertainty in the forecast, said Jessica Schauer Clark, a meteorologist with the hurricane center.

At 1:30 p.m., Hanna was in the southern Bahamas, crawling west-southwest at 7 mph with sustained winds of 75 mph.

The reason the system turned into a hurricane sooner than expected: A nearby low pressure system, which had been creating wind shear and stunting Hanna, dissipated, Schauer Clark said.

As for TD-9, it’s another one we’ll have to watch. Keep in mind that its future track is very uncertain at this point, considering we’ve only seen the initial forecast.

Because it’s still about 2,700 miles away from South Florida, it will be a few days before we even know whether its a legitimate threat.

 

[Skuld]

Yes! Hurricane vacation! awesome!

 

[Ripclawe]

The track forecast for Hanna

The current steering flow driving Hanna to the west is expected to collapse soon, resulting in a slow, erratic motion or small loop for Hanna. By 4-5 days from now, a strong ridge of high pressure is expected to build in, forcing Hanna to the northwest. Most of the long-range models foresee a landfall along the U.S. East Coast late in the week. The most popular model solution (GFS, GFDL, and HWRF) is a landfall Friday in North Carolina, followed by a track up the East Coast. The UKMET model targets South Florida on Friday, and the NOGAPS and ECMWF models target Georgia/northern Florida on Thursday night.

http://www.wunderground.com/blog/JeffMasters/comment.html?entrynum=1054&tstamp=200808

 

[Ripclawe]

Hurricane Hanna
Looking at the satellite loops and wind shear images of Hanna, you'd never suspect that this storm was a hurricane. Hanna is under very high wind shear of 25 knots, thanks to strong northerly upper-level winds that are part of the outflow from Hurricane Gustav. These strong winds have distorted Hanna into an amorphous shifting blob of heavy thunderstorms with little resemblance to a hurricane. Nevertheless, it is a hurricane--the Hurricane Hunters found a central pressure of 983 mb at 3:16 pm EDT this afternoon, with surface winds of 75 mph. However, the shear is so strong that Hanna has not been able to form an eyewall. Recent eye reports from the Hurricane Hunters suggest this process is underway, though.

The track forecast for Hanna
The current steering flow driving Hanna to the west-southwest is very weak, and we can expect erratic motion or a loop over the next two days, in the vicinity of the Bahama Islands. Hanna may move far enough south to hit Cuba, which would seriously weaken the storm. However, only the UKMET model forecasts this, and I'm not counting on Cuba helping the U.S. out again. By Wednesday, a rather strong high pressure ridge will build over Hanna, forcing it to a landfall in the Southeast U.S. Due to the storm's expected rather random motion over the next two days, the location of final landfall has a much higher uncertainty than usual. It is cases like this that really expand the size of NHC's cone of uncertainty, when they go to recalculate the size the cone after hurricane season. So, take your pick of landfall locations:

UKMET, South Florida, Thursday night
GFS, GA/SC border, Friday afternoon
NOGAPS, FL/GA border, Friday morning
GFDL, GA/SC border, Friday morning, Category 3
HWRF, GA, Friday morning, Category 2
ECMWF, GA/SC Friday

These landfall locations have been shifting around quite a bit over the past few days, with North Carolina the favored target yesterday. There have yet to be any model runs showing Hanna recurving out to sea without hitting the U.S. It is likely that Hanna will recurve after landfall, dumping copius amounts of rain on the mid-Atlantic states and New England.

The intensity forecast for Hanna
OK, here are my words from yesterday: "Hanna will not be able to intensify significantly over the next two days, due to upper low it is situated under, and the outflow from Hurricane Gustav." Well, the upper low dissipated, which apparently was enough to allow Hanna to intensify, despite 25 knots of wind shear. It's very unusual to see a tropical storm intensify into a hurricane while under that much wind shear.

The shear is expected to remain 20-30 knots over the next 1-2 days, then decrease to 10 knots by Friday as Gustav weakens and pulls away, reducing the amount of its upper-level outflow that is currently shearing Hanna so much. All the major intensity models respond by intensifying Hanna into a Category 2 or stronger hurricane. This is a low confidence intensity forecast--as is typical for intensity forecasts. I wouldn't be surprised if Hanna drops back down to tropical storm strength Tuesday or Wednesday, due to the shear. As is the case with the track forecast, we don't have a very good idea how strong Hanna might be on Thursday and Friday.

And we got Ike and Josephine coming.