Monday, September 19, 2005

Drought and Flood

5pm update: Rita remains just below hurricane strength, but is expected to reach that level soon, probably tonight. The track is essentially unchanged, but slightly faster.

The long warm, dry spell continues in the Washington metro area. A few showers have been tantalizingly close in the past week. Although National observed rain on 4 consecutive days, only 1 (Thursday) had even 0.01 inch. Those same 4 days also each had double-digit temperature departures above "normal" (long-term average). Temperatures this afternoon are again in the mid to upper 80s, but the official high will likely be a little below the 90-degree level reached 4 times within the last week. The radar is clear in all directions.

Tonight and Tomorrow

Warm conditions will continue through tomorrow, with lows tonight in the upper 60s to around 70. Highs tomorrow will be around 86, and there is only a 30% chance of afternoon or evening showers.

Tropical Beat: "Houston, We May Have a Problem"

With the memory of Katrina fresh, the media are wasting no time recognizing the significance of Tropical Storm Rita. At 2pm, the storm was nearing hurricane strength over the central Bahamas; max winds were near 70 mph and the estimated central pressure was 993 mb. The center was about 380 miles east-southeast of Key West, moving west-northwest around 14 mph. The short-term track is clearly through the Florida Keys into the Gulf, but after that there is a range of opinion. The GFDL model, which has a good record with hurricanes, and the official track, put the storm near Houston by the weekend. However, New Orleans is within the eastern portion of the "cone of uncertainty."

Rita is the earliest 17th storm of the season. The only other one which occurred before Oct. 7 was the tropical storm which formed on Sept. 28, 1933.

Hurricane Philippe is being steered northward east of the same high pressure ridge which is keeping Rita moving westward. This is keeping the minimal hurricane (max winds 75 mph) safely east of the Leeward Islands. It is expected to pass east of Bermuda on Saturday.

To the east, a large area of storms halfway between the Antilles and Africa remains disorganized, and upper-level winds are unfavorable for development.

Broadcast News: Megaflood

Set your TiVo for a different kind of "Storm Stories" on the PBS NOVA program tomorrow at 8pm on channel 26. This is the story of a gigantic flood near the end of the last ice age which sculpted large areas of the Pacific Northwest. Personally, I was unaware of this until I traveled in the region about 10 years ago, but it's an amazing tale of the melting of a glacier thousands of feet thick which had formed an ice dam, creating a lake half the size of Lake Michigan in the basin near what is now Missoula, Montana. The bursting of the glacial ice dam produced a flood as much as a thousand feet deep which shaped hundreds of miles of landscape in eastern Washington state. Recent evidence shows that this pattern of damming and flooding may have occurred repeatedly.

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