Chief Meteorologist, Capital Weather Gang
Monday, September 1, 2008 1:00 PM
Capital Weather Gang chief meteorologist Jason Samenow was online Monday, Sept. 1 to discuss the latest developments regarding Hurricane Gustav and damage in Louisiana, Tropical Storm Hanna, and more.
A transcript follows.
Jason Samenow: Thanks for joining me this afternoon. Hurricane Gustav moved on shore southwest of New Orleans around 11 a.m. with maximum winds of 110 mph. The major impacts so far have included a storm surge of about 10 feet east of the storm's center, reported winds of over 75 mph, with gusts over 100 mph near the storm's center, tornadoes on the east side of the storm, rainfall amount of over 14 in., and some overtopping of levees in New Orleans. These levees, however, have not been breached and no major flooding has yet been reported in New Orleans.
For the D.C. area, of potentially greater concern is Tropical Storm Hanna, which may impact the region by the weekend with wind and rain.
The Capital Weather Gang blog will be providing in-depth coverage of Hanna and its potential impacts in the coming days. I'm happy to take your questions....
AlanGoldberg54: I drove my Chevy to the levee and the levee was wet! But seriously, folks, remember it takes a while for the storm surge and rains to cause damage. In Katrina the levees did not fail immediately -- it took a day or two of heavy rains.
Jason Samenow: This is right on. However, the Army Corps of Engineers seems pretty confident there will not be widespread breaching of levees.
Burke, Va.: What makes the right front quadrant of a hurricane the strongest part of it?
Jason Samenow: The strongest part of the storm coincides with direction of the storm's circulation and its forward direction. Given the counterclockwise circulation of hurricanes and the fact they tend to move from southeast to northwest, the right front quadrant of the storms over eastern North America is usually strongest.
Leesburg, VA: Is it me or does it seem that William Gray's forecast for this year is totally wrong. He is starting to remind me of the Old Farmers Almanac. Thoughts?
Jason Samenow: I think Gray and Klotzbach at Colorado State made a very good forecast. They called for an active season. We've got one!
Washington: What causes the tornadoes on top of the hurricane?
Jason Samenow: The National Hurricane Center has a nice description of tropical storms trigger tornadoes. See:
Yellow Boy: What causes rapid intensification in a hurricane?
Jason Samenow: Several factors:
1) Very warm water
2) Little to no wind shear (or turning of the wind with height which tends to rip apart developing hurricanes)
3) Warm, moist, rising and hence unstable air
Herndon, Va.: I am expected to fly out from Washington to Chattanooga, Tenn., this Sunday. Will either of the storms affect my travel plans? Thank you.
Jason Samenow: It's too soon to say exactly what the timing of any impacts from Tropical Storm Hanna will be in the metro area. If I had to guess right now, I'd say Saturday. But keep checking the Capital Weather Gang blog for updates.
smorrow: I live just east of Mobile. It's pretty bad here, and there are a few tornado warnings already (at about 11 a.m.), but it's a lot worse in Mississippi and New Orleans, and I know there will be a lot of damage there -- but I pray not as bad as Katrina.
Jason Samenow: Thanks for the report from down there. Our thoughts are with you. Many tornado warnings have been issued between eastern Louisiana and the panhandle of Florida. This has been covered to a much lesser extent than the New Orleans flood threat, but is a real concern.
washingtonpost.com: National Hurricane Center
McLean, Va.: So is the hurricane's strength diminishing? It's not another Katrina, right?
Jason Samenow: Yes, now that storm is moving inland, it should gradually weaken. Even if there are some unwelcome surprises with the levees, this will not have nearly the same impact as Katrina as most people got out of harm's way.
Burke, Va.: Can two hurricanes collide? If so, what happens?
Jason Samenow: Hurricanes don't collide. Instead they tend to rotate around one another. This is known as the Fujiwhara effect. More info: http://en.wikipedia.org/wiki/Fujiwhara_effect
Burke, Va.: What is the probability of Tropical Storm Hanna passing through the Washington area?
Jason Samenow: The most likely landfall location for Hanna will be between Jacksonville, Florida and Charleston, South Carolina. While the remnants could impact the DC metro area, the storm should be significantly weaker than at landfall.
The National Hurricane Center has a nice description of tropical storms trigger tornadoes. See : Ya gotta post the link!
Jason Samenow: Let me try again: http://www.aoml.noaa.gov/hrd/tcfaq/L2.html
Arlington, Va.: Why did Gustav never attain the Category 5 strength that was forecast? Is seems the forecasted direction was dead on, but the strength forecast was off quite a bit.
Jason Samenow: The science has a long way to go to improve intensity forecasts. Many forecasters thought Gustav would intensify over the super warm loop current in the Gulf of Mexico. However, dry air wrapped into the western side of the storm and no intensification occurred. The track forecast, on the other hand, was outstanding.
Burke, Va.: Why is the Atlantic Basin so active right now?
Jason Samenow: A number of factors are contributing to the active season:
- Warm water temperatures in the Gulf of Mexico, Caribbean and Atlantic
- A La Nina event, which generally is associated with active Atlantic hurricane season
- We remain in the active phase of a multi-decadal oscillation which began in about 1995
How do hurricanes form?: Why do all North American hurricanes that wind up hitting the East Coast or Gulf Coast seem form off the coast of West Africa near the Cape Verde Islands? What is the so-called "anti-cyclone" near the Azores Islands?
Jason Samenow: In order to get a hurricane, you need some convective weather disturbance to move over warm ocean waters. Many such disturbances originate over the continent of Africa and then develop in the tropical water of the eastern Atlantic. However, some land-falling tropical storms and hurricanes originate from disturbances associated with stalled fronts off of the Gulf and East Coast of North America.
Pittsburgh: Can't a slower hurricane wind up doing more damage by dumping more rain, because it stays longer in one place?
Jason Samenow: You bet... In fact, more people die from inland flooding during hurricanes than storm surge. Link: http://maine.gov/MEMA/mema_news_display.shtml?id=22257
ronljohnson: I'm writing this from a New Orleans suburb at 10 a.m. It's windy, but not even raining. The storm is passing well to the west of the city. The people in the French Quarter, Ninth Ward and Kenner, plus where I live in "Old Jefferson," will not be affected by this storm, except for maybe a day without power. My house is on the east (north) bank of the river, and very close to it. Coming home after Katrina, there was no damage to it -- just a lot of branches in the yard, and a stinky refrigerator ruined by power loss.
My wife and kids went on an evacu-vacation to visit relatives, but I'm staying because there was and is no reason for people on the east bank of the river in New Orleans and Jefferson Parish to leave. However, for the same reason that Gustav won't be affecting me, the people in St. Bernard and Harvey -- closer to canals connecting to the Gulf -- are foolish in the extreme for staying.
Jason Samenow: Thanks for the report. Glad you're staying safe.
washingtonpost.com: Why do tropical cyclones spawn tornadoes? (NOAA)
College Park, Md.: When will the people be allowed to return to New Orleans?
Jason Samenow: That is up to Mayor Nagin and other public officials. But I believe I read on the New Orleans Times Picayune they'd like it to happen as soon as possible -- even within a couple days.
stillundecided08: Let's just remember that just because this storm doesn't seem to be nearly as strong as Katrina (so far), we can't assume that the Gulf Coast has been made safe from future storms. Best of luck to Gulf Coast residents, and let's hope that we're dodging a bullet this time. And by the way ... is there anything washingtonpost.com commenters can't turn political?
Jason Samenow: Agree. It was fortunate Gustav did not make landfall as a Category 4 or stronger hurricane. New Orleans and many other cities along the Gulf coast remain vulnerable. Tampa and the Houston/Galveston area both have huge coastal populations and have not been impacted directly by a major hurricane in a long time.
washingtonpost.com: Hurricane Awareness: Inland Freshwater Flooding (Maine Emergency Management Agency)
Arlington, Va.: Historically with natural disasters, an abundance of caution followed by a less-than-worst-case event have combined to make people more complacent the next time. Ignoring the obvious political overlay here, will those who evacuated and who return to find little wrong claim that the government "cried wolf," and be less inclined to do what they're told the next time (especially if the next time is years from now)?
Jason Samenow: There is always that risk, but as long as the memory of Katrina remains alive, hopefully residents in New Orleans will continue to err on the side of caution. And Gustav may still yet cause damages that will make people glad they left.
Burke, Va.: Where is Hurricane Gustav predicted to go after it makes landfall?
Jason Samenow: It is predicted to slowly drift inland over western Louisiana and into eastern Texas, where there will be a significant inland flood risk.
Brian Jackson: In regards to the high activity, Early September is historically the most active period of the season. As of 11 a.m. we only have two official "named" storms as well as Tropical Depression 9. The record for most storms in the Atlantic basin at once is four.
Jason Samenow: Brian-- That's right. Tropical Depression 9 is forecast to become Tropical Storm and then possibly Hurricane Ike. I think forecasts for an active season will verify as September into early October typically are usually busy.
Annapolis, Md.: How long do you think before Gustav will be reclassified to tropical status instead of hurricane?
Jason Samenow: I would guess within 18-24 hours.
Alexandria, Va.: We're going to New Market on Sunday to watch the VMI cadets take their new cadet oath. Is it likely Hanna will have an impact on the valley that day, or should effects have moved out by then?
Jason Samenow: Most track models have the remnants of Hanna past the Mid-Atlantic by Sunday, but the timing of these forecasts can change... so keep checking Capital Weather Gang updates.
Jason Samenow: Thanks for sending in all of your questions. My apologies for those I couldn't get to. For those of you along the Gulf coast being impacted by Gustav, stay safe.
In the coming days, the Capital Weather Gang blog will continue to provide updates on Gustav, and increasingly, Hanna -- as it could impact Washington, D.C.
washingtonpost.com: Blog: Capital Weather Gang
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