Hurricane Bill

Pre-Landfall 2 | Summary
Posting Date: August 19, 2009, 10:20:00 AM

As of the 11:00 p.m. EDT National Hurricane Center (NHC) advisory on August 18, Bill became the first major hurricane (Category 3 and higher) of the 2009 Atlantic hurricane season. Just six hours later, Bill had strengthened to a Category 4 storm. As of 11:00 a.m. EDT, August 19, Hurricane Bill is located 380 miles east-northeast of the Leeward Islands, moving west-northwest at 18 mph. Maximum sustained winds are 135 mph with higher gusts; hurricane force winds extend outward up to 80 miles from the center and tropical-storm force winds extend out to about 175 miles. Both low wind shear and warm sea surface temperatures—near 82 degrees Fahrenheit (27.5 Celsius)—are conducive to further strengthening. However, the National Hurricane Center (NHC) is estimating only a 10% probability that the Bill will reach Category 5 status. After the 36 hour mark (Thursday at 11:00 p.m. EDT), conditions will become less favorable for the storm to maintain major hurricane strength. The dynamical forecast models indicate that a high pressure ridge should steer Bill northward so that it passes well to the north of the Leeward Islands. The current NHC forecast track has the hurricane passing well west of Bermuda and east of the U.S.’s mid-Atlantic coast on Saturday. However, since Bill is a large system, Bermuda is likely to feel the effects of the storm. The last hurricane to cause significant damage in Bermuda was Hurricane Fabian in 2003. After brushing Bermuda, the current NHC forecast shows Hurricane Bill tracking parallel to the Northeast coast, ultimately approaching Nova Scotia, which it should reach by late Sunday. The AIR tropical cyclone team will continue to monitor Bill’s progress and provide additional information as warranted. Note: As always, there is still considerable uncertainty with respect to the future track and intensity of Hurricane Bill. It is sometimes easy to discount hurricane risk in the U.S. Northeast because hurricanes are relatively infrequent in that region. It is therefore worth noting that Cape Cod is within the NHC’s cone of uncertainty for Bill’s forecast track. The left-hand panel of the figure below shows the NHC’s cone of uncertainty issued as of 11AM today. The right-hand panel shows the westernmost scenario, and the forecast intensity along that potential track. Note that were this scenario to be realized, Bill would approach the Northeast coast of the U.S. as a Category 3 hurricane late this weekend. The forecast intensity just off the Long Island shore is stronger than the intensity at which Hurricane Ike made landfall last year near Galveston. In fact, NHC is forecasting Hurricane Bill to remain a hurricane well beyond the Canadian border.

Pre-Landfall 2 | Downloads
Posting Date: August 19, 2009, 10:20:00 AM