Tuesday, October 18, 2005

Weekend Wilma Worries?

Temperatures this afternoon are about 10 degrees warmer than yesterday in the Washington DC metro area, ranging from 77 to as high as 81 in the southern portions of the region. The only precipitation east of the Mississippi consists of some scattered showers in northern New York and New England.

Tonight and Tomorrow

Under clear skies, temperatures tonight will drop to the low 50s in the city and the mid to upper 40s outside the Beltway. Tomorrow will once again be sunny and dry with highs near 76.

Tropical Beat

Wilma became a hurricane this morning; at 5pm, maximum winds were 80 mph and the storm was moving west-northwest at about 8 mph from a position about 180 miles south of Grand Cayman Island in the Caribbean. Wilma is expected to intensify to major hurricane status (Category 3) as it moves more toward the northwest and into the Gulf of Mexico, eventually turning northeastward toward southern Florida. The storm's impact on our area is very uncertain at this point; that depends on whether it is (1) picked up by a trough in the westerlies and moves up the Atlantic Coast or is (2) pushed offshore to the south.

Climate Clues: A Hard Rain

Image from Meehl et al., Geophysical Research Letters, Vol. 32, L18719.

Today's WaPo has an article describing a study being published online in the Proceedings of the National Academy of Sciences. The study used a climate model to investigate the effects of a doubling of CO2 in the atmosphere by the end of the century. The model predicted that there would be a large increase in the number of extreme heat events and also an increase in the intensity of precipitation. An article in Scientific American online explains that this model increases accuracy from older models by doubling the horizontal resolution from a distance of 50 km between gridpoints to 25 km. By way of comparison, this is almost 16 times the resolution in each horizontal direction compared to what was used routinely in daily weather forecasting just a couple of decades ago.

This study is consistent with one recently reported by NCAR, the National Center for Atmospheric Research, and published in Geophysical Research Letters, which found that precipitation would become more intense with an increase in CO2. The biggest increases would be over land in the tropics. Other areas with large increases include northwestern and northeastern North America.

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