Impressive Bill churning huge waves; New England air pollution episode underway

Hurricane Bill has popped out an impressive eye, and continues to gather strength over the middle Atlantic. Visible and infrared satellite imagery show a well-organized, symmetric hurricane, with plenty of low-level spiral banding and upper-level outflow channels to the north and south. The spectacular appearance of the storm is evidence of the light wind shear environment that Bill finds itself in.

Wind shear is low, 5 - 10 knots, and is forecast to remain low to moderate, 5-15 knots, for the next five days. Sea Surface Temperatures (SSTs) will rise steadily from 27.5°C today to 29°C on Friday. Total ocean heat content also rises today into Wednesday, and it is expected that Bill will take advantage of these favorable conditions to intensify into a major hurricane. The Hurricane Hunters make their first penetration into Bill this afternoon. The NOAA Hurricane Hunters will be continuously flying Bill for the next three days. They are flying research missions that will feed real-time radar data into an experimental version of the HWRF model to see if this data can improve the model forecasts.


Figure 1. Wave forecast for Hurricane Bill from NOAA's Wavewatch III model. Beginning Saturday (right panel) large waves from Bill are expected to affect most of the U.S. East Coast. By Sunday, the model predicts waves of 10 - 15 feet may impact the offshore waters of New England.

Water vapor satellite loops show that a trough of low pressure is diving down towards Bill, and this trough will be able to turn Bill more to the northwest over the next two days, and Bill will miss the Lesser Antilles Islands. The main impact of Bill on these islands will be high waves. Yesterday, Bill passed just north of Buoy 41041, which recorded significant wave heights of 28.8 feet. Maximum wave height is typically a factor of 1.9 greater than the significant wave height, so Bill was likely generating waves up to 55 feet high. High waves from Bill are propagating across the Atlantic towards the U.S. East Coast, and will arrive there on Saturday, according to NOAA's Wavewatch III model (Figure 1). The highest waves spawned by Bill will affect the New England coast, where waves of 10 - 15 feet in offshore waters can be expected. The waves will cause significant erosion of beaches, and possible damage to shoreline structures.

A much larger trough of low pressure is expected to develop along the U.S. East Coast late this week, turning Bill to the north. Exactly where this turn occurs is still not clear, and both Bermuda and Cape Cod, Massachusetts will be in Bill's 5-day forecast cone of uncertainty. At present, it appears that the Canadian provinces of Newfoundland or Nova Scotia are at greatest risk from a strike by Bill, but New England and Bermuda cannot relax just yet.

Elsewhere in the tropics
The remains of Tropical Storm Ana are bringing heavy rain to Haiti, Cuba, and the Bahamas today, and this activity will spread over South Florida tonight. The remains are disorganized, and are not likely to re-develop. No models are calling for any new tropical cyclones to develop in the Atlantic over the next seven days.


Figure 2. Image from NASA's Terra satellite of air pollution haze over the Northeast U.S. on Monday, August 17, 2009.

First major air pollution episode of the summer for the Northeast U.S.
New England is currently experiencing a far more deadly weather event than a direct hit by Hurricane Bill would likely bring--a large dome of high pressure. The reason? The high pressure system camped over the Northeast U.S. has brought hot temperatures, stagnant air, and the summer's first major air pollution episode.

The event started on Sunday, when a high pressure system with light winds moved over the eastern U.S., limited mixing and leading to stagnation and a buildup of pollutants. Mostly sunny skies and high temperatures also enhanced formation of ground-level ozone gas, a dangerous pollutant. Furthermore, southerly winds brought high humidity into the Northeast, which is conducive to particle pollution formation in the atmosphere. Particle pollution is the most deadly form of air pollution in the U.S. The poor air quality led to issuance of air quality advisories and action days on Monday in more than 30 cities, including New York City, NY; Newark, NJ; Providence, RI; and Portland, ME.

Today's air pollution forecast
Today, similar conditions are expected across much of the region, and Air Quality Index (AQI) levels are forecasted to remain in the Unhealthy for Sensitive Groups (Code Orange) range for many areas in the Northeast. For a complete list of action/advisory days and their locations, visit the EPA AIRNow website.

Health Tip: Cut back on strenuous outdoor exercise when air quality is expected to be poor.

How You Can Help: Choose a cleaner commute - share a ride to work or use public transportation. Bicycle or walk when possible. Combine errands and reduce trips.

Mortality from air pollution
As I discussed in a previous blog post, air pollution is a far more deadly weather hazard in the U.S. than hurricanes. Sure, hurricanes have killed an average of 150 people per year in the U.S., and the "premature deaths" caused by air pollution are only partly attributable to breathing bad air, while drowning in a hurricane's storm surge is entirely due to the hurricane. Nevertheless, a great many children die of pollution-induced asthma attacks who would not have died otherwise, and the mortality due to air pollution in the general population is in the thousands or ten of thousands each year. Outdoor air pollution in the U.S. due to particulate pollution alone was estimated by the EPA in 1997 to cause at least 20,000 premature deaths each year. A 2005 study by EPA scientists (Particulate Matter Health Risk Assessment for Selected Urban Areas) estimated that over 4,700 premature deaths occur each year in just nine cities (Detroit, Los Angeles, Philadelphia, Pittsburgh, St. Louis, Boston, Phoenix, Seattle, and San Jose)--even if those cities all met the current federal standards for particulate matter pollution. Extrapolating these data to the entire nation puts the annual death toll in the tens of thousands--but the EPA has not calculated that total. Some studies have placed the annual pollution death toll in the U.S. at 50,000 to 100,000 (Dockery, D.W., and C.A Pope III. Acute Respiratory Effects of Particulate Air Pollution. Annual Review Public Health, 1994, vol. 15,107-32.) The death toll is much higher in other parts of the world, where air pollution standards are not as stringent. Globally, about 800,000 people per year die prematurely due to outdoor air pollution, according to a 2005 study published in the Journal of Toxicology and Environmental Health. This represents about 1.2 percent of total annual global deaths.

In the debate over the costs of switching over the cleaner energy sources, the huge costs and deaths attributable to air pollution are often ignored. Sure, it will be costly to move away from fossil fuels, but let's not forget that the price per gallon we pay at the pump does not include the billions in medical costs we pay for the effects of air pollution.

I'll have an update Wednesday morning.

Jeff Masters