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Chat wrap: WMAR's Norm Lewis

SunSpot: Thanks for joining us today.

Lewis: I appreciate it.

Mike, Ellicott City: Can you give us the thumbnail explanation of how high and low pressure systems steer or block a hurricane?

Lewis: High pressure acts like a bumper, so storms bounce off of it or are steered around it. Low pressure acts like a vacuum cleaner and actually sucks a storm in that direction.

David, Fells Point: Right now it is a clear sunny day. When will the wind and rain start here in Baltimore?

Lewis: Rain should start in the Baltimore area between 2 and 4 tomorrow afternoon and get progressively heavier through the evening.

Various readers: Can you tell us specifically how the storm will affect our area?

Lewis: The primary effect on our area is going to be from heavy rainfall, which is going to result in flooding. That's not to say that the whole area is going to flood, just areas that are subject to flooding will flood. Obvious concerns are Ellicott City, which is prone to flooding; the Elkton area; Port Deposit; the Frederick region. All the rain that falls to the west of us is going to come towards the bay.

Phil, Woodbine: Given that the projected track of Isabel is very similar to that of the 1933 hurricane that resulted in seven feet of water at the corner of Pratt and Lombard, why aren't more specific warnings being made to downtown residents and visitors about the possible severity of these conditions? It appears that Isabel will be an even stronger storm than 1933; therefore, shouldn't the expected surge be even greater?

Lewis: The answer to that is no. And the reason being is drainage from storm drains increased flow rate of the Jones Falls. The Gunpowder River, Patapsco, and the Monocacy have a greater capability of carrying runoff now than they did in '33. Also, this storm is not going to last as long as the '33 storm.

SunSpot: Isn't the storm curving more off to the west, also?

Lewis: That is true, it is going more to the west. But that is potentially more of a problem in that the storm clouds, once they hit the mountains, are physically pushed up in the atmosphere which cools the cloud and makes even more rain come out of the storm than if it was over a flat area. It's called "orographic lifting."

Jeanne, Baltimore: How does the amount of rain forecast for Isabel compare with the rainfall the area received during Hurricane Agnes?

Lewis: The rainfall in Agnes was much greater than what we're going to see from Isabel because Agnes was over us for three days and Isabel is only going to be over us for 18 hours.

Andrew, Edgemere: I've heard a lot about the storm surge. Since I live in a low-lying area that is adjacent to tidal water, how much surge can I expect from Isabel? And, will this be a "raging wall of water," or will it be more like an extremely high tide?

Lewis: First off, it'll be like an extremely high tide and being as the center of the storm will be passing west of the area, the winds will be from the northeast, which will have the effect of pushing water out of the bay, rather than into the bay. There's a caveat on that: when you push all the water out of the bay, when the winds reverse on the back side of the storm, the water will come back in but it's not as much of an effect as if you were on the coast and had the whole ocean coming up on you. You only have a fairly small body of water with the bay.

Cheryl, Perry Hall: I heard that the Inner Harbor is already experiencing some flooding from the rain we had last week. Is there any chance that the rain will be so great that it could flood Pratt Street? How high could it get down here?

Lewis: First off, there's no way to tell exactly but it would not be at all unusual with the amount of rain that we're expecting to get six inches of water in the downtown area.

Mark, Silver Spring: We've heard a lot about how to protect a home. What about the large number of people who live in high-rise apartments? Are we at risk from breaking windows, especially on the upper floors? How strong does the wind have to be to blow in a window?

Lewis: Windows are traditionally not blown in. Windows are usually broken by flying objects, which is the reason that we ask people to pick up their lawn chairs, potted plants, and all that kind of stuff. A window can usually withstand 130-150 mph winds.

Phil, Rosedale: What conditions on the west coast of Africa cause storms like Isabel to be created during this time of year?

Lewis: It's a differential of the land temperature and the water temperature combined with the winds that circulate in the inner tropical convergence zone, the area between 15 degrees north and south latitude. Air flows toward the equator from the poles to this convergence zone. When these currents combine, they can create a spinning motion that can circulate across the equator to eventually spawn hurricanes.

Bea, Crownsville: What kind of wind speeds can we expect in the Baltimore area?

Lewis: Between 30 and 50 mph, with some gusts possible to 70 mph. As long as their are no projectiles in this wind, things aren't too bad. If you pick your neighbor's garbage can up in that, it can do a whole lot of damage. Most people don't realize most fatalities in hurricanes occur due to drowning, not winds or projectiles.

Rob, Eldersburg: Why does warm water add fuel to a hurricane?

Lewis: If you think of a pot of boiling water, the steam coming off the water goes upward. The same thing happens in a hurricane, except it's not boiling water. It's sucking heat up inside the storm and the heat in the water is what makes the storm run.

Tim, Baltimore: As a local meteorologist, which is harder: predicting the path of Isabel, or predicting on any given Tuesday whether it will rain on Saturday?

Lewis: It's much harder with Isabel because there's much more at risk. If I tell you it's going to rain on your picnic and it doesn't, it's no big deal. If we tell you Isabel is arriving Thursday and you make all the preparations, you're a very unhappy person. We have gotten much, much better in the science of meteorology. The forecasting from day to day has gotten much better.

Monroe, Roland Park: Why are hurricanes given names?

Lewis: They were given names starting back in the 1950s because all of meteorology is based on numbers. When you assign a name to a hurricane, it can't be confused with anything else. Names are sometimes retired: Hugo, Andrew, Camille, those Category 5 storms that go down in the history books are retired.

SunSpot: So is this storm going to be similar to Floyd, the last hurricane to affect this area?

Lewis: This is probably going to be stronger than Floyd and affect a larger area. This will affect counties out to the west of us, sending a lot of water in our direction afterwards. If you want a storm to compare it to, it's going to be very similar to David, which hit in 1979.

SunSpot: Any last thoughts for our readers?

Lewis: People shouldn't panic with the storm. Pick up around the house, make sure you have whatever supplies you might need for a 24-hour period of time and also, again, the primary problem from this storm is going to be coming from flooding. If you live in a low-lying area, be aware. This is not going to be a killer storm, but it is going to be more wind and rain than we've seen here in a long time. Just use your head. Don't drive into water that's over the road.

SunSpot: Thanks again for joining us.

Lewis: Certainly. It's been fun.

About Norm Lewis
Norm Lewis, the chief meteorologist for WMAR's 2News, grew up in Florida near the town of Melbourne but has been in Baltimore since 1979.

For more on Norm Lewis, visit his page on

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