Daily Archives: September 4, 2008

The Night Before Hanna

Here’s tonight’s briefing:

We’re down to the wire, folks. Things are looking fairly stable at this point to landfall. The 11PM advisory did not change much at all from the 5PM and 8PM advisories. The track’s pretty much the same (save for the inevitable wobbling tropical systems do as they approach). There’s a chance the wind field may contract a little (see the NHC discussion for more); Hanna’s getting its tropical characteristics a bit more in order. (I’m still shocked it’s not being classified as subtropical, personally…)

The time for speculation is indeed over, though. Now, we wait and see and let Hanna do what she’s going to do.

I’ll start coverage on Charleston Weather at roughly 10:30 to 11:00 tomorrow morning after I catch up on a bit of sleep. Watch this space for blog recaps as conditions deteriorate, and pay close attention to the Charleston Weather Twitter account, as well as my own personal Twitter account. If I should lose power, I’ll still be able to update my Twitter accounts for as long as my BlackBerry has juice. I may charge some backup phones tonight as well, just in case. The chat room is always open for business, and I’ll try to stay in there as long as I can. Tomorrow promises to be interesting.

11am: Hanna barely clinging to tropical characteristics

Hanna’s looking rough this morning. It’s back down to 65 MPH winds, and there’s a lot of speculation that Hanna is becoming extratropical. NHC acknowledges Hanna’s struggle to remain tropical in the discussion:

VERY DRY AIR ASSOCIATED WITH THE UPPER-LEVEL LOW OVER THE
NORTHWESTERN BAHAMAS IS CHOKING OFF CONVECTION NEAR THE CORE OF
HANNA…AND THE CYCLONE HAS A VERY SUBTROPICAL APPEARANCE.
CONVECTION HAS DIMINISHED SUBSTANTIALLY OVER THE PAST 6-12 HOURS
AND THE HIGHEST FLIGHT-LEVEL AND SFMR WINDS HAVE COME DOWN AS WELL.
BASED ON SOME 52 KT SFMR WINDS AROUND 11Z…THE INITIAL INTENSITY
IS LOWERED TO 55 KT.

Here’s the latest track, which returns more to the rightward path that we started seeing emerge during the day yesterday before the 11:00 came out:

The wind field is still pretty broad — 310 miles, to be exact — but largely to the north and northeast. We in Charleston still stand a decent chance of seeing tropical storm force winds for a time, and some rain, but with the dry air influencing the storm as well as the continued rightward bias in the models, impacts along our coast will be lessened.

News 2 reports that Gov. Mark Sanford has called for voluntary evacuations of Horry and Georgetown counties; he also said that Hanna might be a “dress rehearsal for a thing called Ike.” Ike is bothersome to me; I’m crunched for time now but will have more later on.

5am: Hurricane watches now up for the area

5am Hanna Watches

As of 5am, hurricane watches are now up from Surf City, NC, to just north of Hilton Head, SC. Tropical storm watches extend from roughly Hilton Head down to almost the Georgia/Florida border.

Hanna’s still a 65 MPH storm, headed to the northwest at 11 MPH. Its satellite presentation has been less than impressive this morning; however, strengthening is still fairly likely and Category 1 strength at landfall is to be expected.

Tropical Storm Hanna 5am 09/04:  Wind Field

The 5am track speeds up the timeline a bit and shifts landfall slightly left. As of now we’re looking at a landfall a bit closer to the NC/SC border (almost right on top of Wilmington) around 2am Saturday. Tropical storm force winds should begin to arrive in Charleston around noon tomorrow, or so. Today is another clear day, so today is the day to finish your preparations. Conditions will turn drastically downhill as Friday comes along. On the current track — still very subject to change — the center of the storm will probably pass to the east of here from around 7 to 9 PM Friday night. Once this occurs, conditions will begin to improve as Hanna’s not expected to have much on its southwest side.

More after 8 or so with the new model runs and the intermediate advisory.

11 PM: Hanna begins northwest turn; watches likely tomorrow

Tropical Storm Hanna 11PM Advisory 09/03:  Satellite Photo

The 11PM advisory is now out on a steadily reorganizing Hanna. Winds remain around 65 MPH, and pressure is sticking around 989 millibars. The Turn has really started to happen, as NHC states forward motion is north-northwest at 13 MPH.

The Track

Tropical Storm Hanna 11PM Advisory 09/03:  Track + Uncertainty Cone

The track seems to have shifted a bit more leftward before landfall; there’s still a fair bit of uncertainty. In the discussion, NHC acknowledges low confidence in the track, citing some spread in the forecast models.

Tropical Storm Hanna 11PM Advisory 09/03:  Forecast Models

There’s good consensus for a turn to the north and then the northeast; the big question is where it will happen. There’s decent consensus heading toward Wilmington, but there’s spread on the western periphery of the consensus — including a HWRF model that generally gets a fair bit of weight from NHC forecasters — hence the uncertainty and the slight leftward jog in the track.

NHC is saying that hurricane watches are likely for a “large portion of the southeast US coast” by tomorrow morning. It’s probably safe to assume that we in Charleston will be included in this watch.

It’s worth noting that the storm will be relatively short-lived; it’ll be increasing in forward speed throughout its approach. In Charleston, it’s likely that Hanna will have largely cleared the area by Saturday night. This is good for reducing the threat of severe flooding. There will still be heavy rains, but at least they will be short-lived.

Effects

Charleston should start feeling effects from Hanna as Friday wears on. As it gets closer, winds will increase. I’ve been able to use an experimental forecast wind field product as a decent guideline for what we might see here.

Tropical Storm Hanna 11PM Advisory 09/03:  Forecast Wind Field

The forecast says that we’ll see some of the worst of the weather Friday night into early Saturday morning, as the center passes within 75 miles or so of Charleston. Sustained winds of 58 miles per hour or greater — as indicated by the purple shading in the map above — are possible for a brief period. As mentioned above, rain totals will probably hit 6″ in some places, but this won’t be a storm that sits and spins and dumps 30″ of rain like a Fay over Florida.

Again, a lot of this is contingent on something resembling the current track holding. There’s more time for stuff to wobble back and forth, and Charleston is still in the cone of uncertainty, so there’s still stuff to watch. However, the direct strike scenario is looking less and less likely.

Closures, etc.

Keep an eye to media outlets and other sources for closure information in the Charleston area tomorrow, as I expect most of those closures (or lack thereof) would be announced during the day. A good resource for this is the @news2 Twitterstream.

Check out Lowcountry Bloggers’ Storm Buzz

The Lowcountry Bloggers roundup site has launched Storm Buzz, an automated feed of hurricane-related posts from the Lowcountry blogosphere. This is a good one-stop resource to see what Charleston bloggers have to say about Hanna and Ike.

Speaking of Ike…

Ike exploded into a dangerous but equally gorgeous Category 4 storm during the day Wednesday. It’s in a perfect environment for strengthening and could be a 5 before it’s all said and done. It’s expected to weaken to a 3; tentatively, it’s headed to the Bahamas, but there’s a lot of spread and uncertainty. It could recurve out into the sea — which would be ideal, of course — or it could threaten the U.S. within the next five or so days. Ike is one to watch because it’s expected to retain major hurricane status as it traverses the Atlantic, with fluctuations in intensity characteristic of huge storms.

For now, though, all eyes will continue to be on Hanna as she makes her move toward the coast. I’ll have more in the morning, probably shortly after the 8am advisory unless there’s a major shift in track that needs immediate attention.

Coverage Continues

Another video briefing will be broadcast at about 9:15 PM, with a roundup of the day’s information and hopefully a better fix on what Hanna’s going to do. She’s still got a history of behaving badly and needs to be watched closely.

Coverage will be more frequent as conditions deteriorate; I’m planning on bringing in additional folks to assist with coverage. Additional streams are planned for as long as power is viable. Now’s the time to follow @chswx and my own personal Twitter account for information and accounts of the storm, too.