August 18, 2009
Scattered Code Orange Ozone and PM2.5 in the Northeast; Smoke/Haze Persists along East Coast; Bill Becomes a Major Hurricane in the Caribbean
The widespread area of smoke and haze persisted over the Northeast today, extending a period of Code Orange (Unhealthy for Sensitive Groups) ozone and PM2.5 air quality that began on Sunday. Several metropolitan areas saw Code Orange conditions today, as shown in the loops of AQI values (ozone below on left; PM2.5 below on right). This air quality event has been the first significant extended period of poor air quality in the Northeast and Mid-Atlantic this summer, which is remarkable compared to past years, when 4-5 events typically might have occurred by this point in August.
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The haze/smoke mixture is apparent in today's Terra MODIS true color image (below on left, overlaid with AQI values in Google Earth), extending along the East Coast and out over the Atlantic from North Carolina to Maine. The corresponding MODIS AOD image (below on right) confirms the high concentrations of particulates associated with the hazy airmass.
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Fire activity is relatively quiet today. NOAA's Hazard Mapping System (HMS) reports that wildfires in central California are producing light to moderately dense smoke that is mixing in with blowing dust, extending into western Nevada.
Out in the Caribbean, Hurricane Bill has just become a major hurricane. The National Hurricane Center issued an update at 8:30 PM AST; data from the NOAA hurricane hunter aircraft that investigated Bill this afternoon indicates that the hurricane has strengthened, with maximum sustained winds of near 125 mph (205 km/hr). Bill is now a Category 3 hurricane on the Saffir-Simpson Hurricane Scale. It's a classical-looking storm, as you can see from a GOES visible satellite image of the Caribbean from this morning (below on left). Currently, Bill is not forecasted to make landfall in the U.S. (5-day forecast cone is below on right), but we will monitor the westward extent of Bill's periphery as it moves north through the Atlantic. Subsidence along the edges of a hurricane's circulation limits vertical mixing and cloud cover, and as a result, ozone formation can be enhanced.
Update: Bill has strengthened to a Category 4 hurricane on the Saffir-Simpson scale, as of 5 AM AST, Wednesday.
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