Wednesday, August 31, 2005

Weather columnist Kevin Myatt: No tornadoes for Southwest Virginia

Multimedia: Live hurricane tracker

By Kevin Myatt
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Kevin Myatt is The Roanoke Times' weather columnist.

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Wednesday 7:30 a.m. -- Southwest Virginia did not become part of Katrina’s legacy of misery and devastation on Tuesday as the ingredients didn’t quite come together right for tornadoes.

The best atmospheric dynamics for the rotating winds of tornadoes were to our west. The best instability for the development of thunderstorms capable of spawning tornadoes was to our east. The thought during the day Tuesday was that those two things would be best married right up and down the I-81 corridor. Those factors didn’t quite hook up.

We got some squally rain in our area, but no real severe weather. There was more to our northeast, with at least one apparent tornado damage report from Faquier County. This was not the outbreak it could have been. We should be thankful.

Much drier weather appears to be on the way beyond the last showery leftovers of Katrina today. Fortunately, drier weather is moving into the devastated Gulf Coast region, too, which faces rebuilding from a disaster of immense proportions – described as the “most significant natural disaster in U.S. history” by one FEMA official.

Katrina the hurricane is over, but Katrina the disaster will linger for months and maybe years.

Tuesday 9:30 a.m. -- In my six years here, I have never before seen our area placed under a moderate risk of severe weather by the Storm Prediction Center -- but that is the reality today. Check this map out.

The SPC is particularly mentioning the possibility of strong winds and tornadoes, as shear produced by the conflicting upper-level winds of now-Tropical Storm Katrina induce rotation in developing storms today.

If the sun comes out through the blanket of low clouds and we get some heating today, things could erupt quickly.

The thing to do today is just to stay tuned to media outlets in case watches and warnings are issued. If a tornado warning is issued for your locality, go to an interior room on the lowest floor away from windows.

This is potentially dangerous situation ... but just that, "potentially." Potential sometimes is realized; sometimes it isn't.

On the bright side, we won't have large-scale flooding to worry about today, though heavy downpours in some storms could cause localized flooding.

Links:

Latest infrared satellite image of Katrina:

Latest radar out of New Orleans

Latest projected track

7 p.m. -- While the damage situation on the Gulf Coast slowly becomes clearer – little has been heard yet out of the hardest hit area of Missisippi’s southwest Gulf Coast – it’s time to turn our attention to what we can expect.

There appears to be a growing risk of severe thunderstorms, with possible tornadoes, in our area on Tuesday afternoon. If we get considerable daytime heating, there will be enough moisture for thunderstorms to begin developing. Katrina’s leftover spin may also be enough to create atmospheric rotation that could cause some of these storms to spin, possibly producing isolated tornadoes. This isn’t a sure bet, but enough that the Storm Prediction Center in Norman, Okla., considers western Virginia and several surrounding states a “Slight Risk” area on Tuesday.

(Severe storms risk map, Day 1)

The main bulk of Katrina’s moisture appears to be going to our west, so flooding rains are not likely, though locally heavy rains may occur. Widespread flooding is not expected, and any local flooding would probably be brief. We’re just not going to get the middle of this system, but instead, the periphery.

I’ll update Tuesday morning on the latest with Hurricane Katrina.

11 a.m. -- The eye jogged just a little west after its initial landfall near Grand Isle, La., and as a result, New Orleans got caught in the western eye wall and is incurring severe wind and flood damage currently.

The western eye wall is a slightly better place than the eastern wall, which is plowing toward Pass Christian, Miss., where near-catastrophic destruction is likely occurring. Pass Christian was also ground zero for Hurricane Camille in 1969. The mayor of Gulfport, Miss., has declared Katrina as “Camille 2,” according to the Associated Press, saying that boats have been washed into houses. A Weather Channel crew, located at 27 feet above sea level in Gulfport, has reportedly been inundated by the storm surge and is helping sandbag. That would put this storm surge as very similar to that of Camille, maybe a bit more.

As the scene continues to unfold, I have little doubt that this storm – with major damage occurring from Mobile to west of New Orleans – will surpass Andrew in monetary damage for the costliest natural disaster in U.S. history. Hopefully, evacuations and warnings will limit the death toll to a small number.

For Southwest Virginia – the Storm Prediction Center considers areas along and west of I-81 in a slight risk for severe thunderstorms on Tuesday, including tornadoes. We have to watch if the storm jogs to the east inland, which would increase impact in our area.

Katrina will be a major disaster for locations far from the Gulf Coast. Right now, it looks like the main area of concern will be far west of us, but let’s don’t lose sight of this monster.

Monday, 9:30 a.m. -- New Orleans will fare poorly, but will probably come out better than it could have, with Hurricane Katrina down to “only” a Category 4 storm (131-155 mph winds) and its center scraping along east of the city. New Orleans, at this writing, is taking wind gusts over 100 mph with widespread damage developing, but this won’t be the absolutely catastrophic hit that was feared. It will be a close call whether the city’s seawall can handle the overflow from Lake Ponchartrain when the north winds on the western side of the storm begins to pull the lake’s water toward the below-sea-level downtown.

I’m more concerned about the Mississippi Gulf Coast, which is already catching gusts over 100 mph well away from the storm’s center, and will be on the eastern eye wall. The Mississippi Gulf Coast will see the biggest storm surge it has seen since Hurricane Camille in 1969, when a 25-foot storm surge roared inland. This area is much more heavily built-up that it was in Camille, with a thriving casino industry, so expect many billions of dollars in damage.

With the combined size and strength of Katrina, I fully expect that when the cost is counted, it will challenge or possibly exceed the $36 billion in damage caused by Hurricane Andrew in South Florida in 1992.

The damage will not be limited to coast. Inland areas of Mississippi, Alabama and Tennessee can expect hurricane-force winds, flooding rains and tornadoes.

As for Southwest Virginia, we need to watch how fast Katrina begins to curve northeast inland. A harder, faster turn than expected could throw heavier effects our way Tuesday or Wednesday, as the storm could travel as far east as the western slopes of the Appalachians. More likely, the remnants of Katrina will inundate Tennessee, Kentucky and Ohio, with our area getting some squally rains and thunderstorms as southeast winds drawn into Katrina pull abundant tropical moisture upslope on the Piedmont and mountains. Some of Katrina’s actual rain bands could move into the area by Tuesday night or Wednesday, especially west of Roanoke.

While this storm is comparable to Camille in strength and landfall location, it will not comparable to Camille in its flooding in Virginia. Unlike with Camille, strong winds aloft will begin to speed up Katrina after she moves further inland. What’s left of this mighty storm will be in Canada by Thursday.

Sunday, 3:30 p.m. -- The nightmare of nightmares for U.S. hurricane disaster planners is closer to happening than it ever has been today.

A Category 5 hurricane with 175 mph winds and gusts over 200 mph appears to be zeroing in on the New Orleans area or Mississippi Gulf Coast. New Orleans has long been considered the worst imaginable U.S. target for a hurricane of this strength, with its heavy population on below-sea-level land and major water bodies on three sides.

It is still possible that Katrina could weaken some before landfall on Monday … but a Category 4 strike (131-155 mph winds) to that heavily built up and populated region would still be an immense disaster. With hurricane-force winds now up to 150 miles from the center of the storm, it would take a large shift in the track to spare warned areas from major devastation.

“Katrina is comparable in intensity to Hurricane Camille of 1969 … only larger,” a National Hurricane Center forecaster wrote in a discussion of the storm this morning. Camille is one of three Category 5 hurricanes to hit the U.S., along with Andrew of 1992 and the Labor Day Hurricane of 1935.

This storm’s path is also very similar to Camille, which made landfall at Pass Christian, Miss., east of New Orleans and devastated the Mississippi Gulf Coast with nearly 200-mph winds and building-submerging storm surge. That kind of castastrophe is quite possible again.

There is some hope that Katrina may pull in some dry air near landfall, weakening her intensity some. But there appears to be nothing out there, short of divine intervention, that can sap enough energy out of Katrina to make her fizzle … and a fizzle at this point would be “only” a Category 3 storm (111-130 mph). “Only” a Category 1 storm killed 7 people in Florida on Thursday.

In Southwest Virginia, we may get some heavy rain from Katrina on Tuesday and Wednesday. It will begin to pull moist southeast winds up the slope of the Piedmont and Blue Ridge, and this could squeeze out some heavier showers and storms. The core of Katrina’s remains is expected to pass west of our area, but a cold front will help push some tropical moisture our way. There is still enough uncertainty in the inland path that we could yet get a more serious effect from Katrina, so stay tuned.

I’ll leave you with this: The National Weather Service in New Orleans issued the most frightening special weather statement I’ve ever read this morning. It says better than I ever could what may happen if Hurricane Katrina broadsides New Orleans at its current Category 5 strength. Here is that statement, verbatim:

... DEVASTATING DAMAGE EXPECTED ... HURRICANE KATRINA ... A MOST POWERFUL HURRICANE WITH UNPRECEDENTED STRENGTH...RIVALING THE INTENSITY OF HURRICANE CAMILLE OF 1969.

MOST OF THE AREA WILL BE UNINHABITABLE FOR WEEKS...PERHAPS LONGER. AT LEAST ONE HALF OF WELL CONSTRUCTED HOMES WILL HAVE ROOF AND WALL FAILURE. ALL GABLED ROOFS WILL FAIL...LEAVING THOSE HOMES SEVERELY DAMAGED OR DESTROYED.

THE MAJORITY OF INDUSTRIAL BUILDINGS WILL BECOME NON FUNCTIONAL. PARTIAL TO COMPLETE WALL AND ROOF FAILURE IS EXPECTED. ALL WOOD FRAMED LOW RISING APARTMENT BUILDINGS WILL BE DESTROYED. CONCRETE BLOCK LOW RISE APARTMENTS WILL SUSTAIN MAJOR DAMAGE...INCLUDING SOME WALL AND ROOF FAILURE.

HIGH RISE OFFICE AND APARTMENT BUILDINGS WILL SWAY DANGEROUSLY...A FEW TO THE POINT OF TOTAL COLLAPSE. ALL WINDOWS WILL BLOW OUT.

AIRBORNE DEBRIS WILL BE WIDESPREAD...AND MAY INCLUDE HEAVY ITEMS SUCH AS HOUSEHOLD APPLIANCES AND EVEN LIGHT VEHICLES. SPORT UTILITY

VEHICLES AND LIGHT TRUCKS WILL BE MOVED. THE BLOWN DEBRIS WILL CREATE ADDITIONAL DESTRUCTION. PERSONS...PETS...AND LIVESTOCK EXPOSED TO THE WINDS WILL FACE CERTAIN DEATH IF STRUCK.

POWER OUTAGES WILL LAST FOR WEEKS...AS MOST POWER POLES WILL BE DOWN AND TRANSFORMERS DESTROYED. WATER SHORTAGES WILL MAKE HUMAN SUFFERING INCREDIBLE BY MODERN STANDARDS.

THE VAST MAJORITY OF NATIVE TREES WILL BE SNAPPED OR UPROOTED. ONLY THE HEARTIEST WILL REMAIN STANDING...BUT BE TOTALLY DEFOLIATED. FEW CROPS WILL REMAIN. LIVESTOCK LEFT EXPOSED TO THE WINDS WILL BE KILLED.

AN INLAND HURRICANE WIND WARNING IS ISSUED WHEN SUSTAINED WINDS NEAR HURRICANE FORCE...OR FREQUENT GUSTS AT OR ABOVE HURRICANE FORCE...ARE CERTAIN WITHIN THE NEXT 12 TO 24 HOURS.

ONCE TROPICAL STORM AND HURRICANE FORCE WINDS ONSET...DO NOT VENTURE OUTSIDE!

Sunday morning -- Hurricane Katrina began making its northward turn Saturday evening, and the storm had all the makings of a disastrous hit for the Louisiana, Mississippi or Alabama coast.

But Katrina traveled farther west than initially expected before making that turn, so the threats to our area from what’s left of Katrina at midweek are lessened. Rain, yes, some thunder, but at this point, probably not much in the way of gusty winds or a tornado threat. Flooding is still a possibility, but with a ground that was pretty dry before the rains of the last couple of days, it would take a lot of rain to cause any flooding approaching what we remember with Jeanne of last September. Katrina, even if its core were to pass right over, might be moving too fast to dump a huge amount of water on us. The infamous flooding storms of Virginia’s past, like Juan in 1985 and Camille in 1969, were slow movers, or even no movers.

Katrina will be swept northward as a dip in the jet stream digs toward the middle of the country, pushing a cold front along with it. Katrina’s remnants will slide north and northeast along this cold front into the Tennessee Valley and Ohio Valley by Tuesday and Wednesday, and some of that moisture will probably make it into Southwest Virginia as well.

Katrina’s lasting legacy will be what she ends up doing to the north-central Gulf coast, with a projected landfall on Monday or Tuesday. New Orleans will get a lot of attention, since it is the biggest city in the threat area, hasn’t been directly nailed by a major hurricane in many decades, and is viewed by many experts as the nation’s number one hurricane nightmare with its below-sea-level land amid three major bodies of water (the Gulf of Mexico, the Mississippi River, and Lake Pontchartrain). But Katrina will likely be a paralyzing disaster wherever she comes ashore.

Even in Southwest Virginia, don’t take your eyes off Katrina entirely yet. A modest wiggle to the east could bring her back into play for our area.

You can keep up with the latest on Katrina via the National Hurricane Center link, listed as “Tropical Storm Updates” at the upper left of this column.