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Hurricane Irene slides toward Bahamas; Strong earthquake rattles eastern U.S.

By: Dr. Jeff Masters, 9:57 PM GMT on August 23, 2011

Hurricane Irene is a category 1 on the Saffir Simpson scale as of 5pm EDT, with maximum sustained winds of 90 mph and a minimum central pressure of 976 mb. Irene is moving to the west-northwest at 9 mph, and continues to impact Hispaniola. Satellite imagery shows a strong rain band continuing to linger over the eastern Dominican Republic on the southeast side of Irene, but wind speeds appear to have decreased substantially in the country since this morning. Winds are gusting to around 50 mph in the Turks and Caicos Islands this afternoon. Wind shear is currently around 10-20 knots in the vicinity, which could delay intensification over the next 48 hours. The strongest winds and thunderstorm activity remain on the northwest side, and the eye that was visible on satellite earlier today has become obscured by new thunderstorm activity near the center of the hurricane. The most recent Hurricane Hunter mission found a minimum central pressure of 978 mb and a large wind field. In their 2pm EDT fix, the National Hurricane Center estimated that tropical storm-force winds extended 180 nautical miles from the center in the northeast quadrant of the hurricane. A NOAA Gulfstream plane (Gonzo) is currently flying Irene and providing dropsonde data, something that was critical in gaining model consensus yesterday. A NOAA P-3 (Kermit) is also on its way to the hurricane to provide dropsonde data, as well.

Figure 1. Satellite imagery of Hurricane Irene at 4:45pm EDT. Image credit: NOAA.

Track forecast for Hurricane Irene
Models are in better agreement on the track forecast for Irene today, although the GFDL and HWRF continue to be the western outliers. Both of these models are forecasting Irene to make landfall near the Outer Banks of North Carolina on an almost due north track. The rest of the global models continue to slide every so slightly east in their forecast track, with some not making landfall until the hurricane is as far north as Long Island. This afternoon, the ECMWF, which has been performing well this season, forecasts Irene to brush the Outer Banks before sliding up the east coast toward New York. The official track forecast from the National Hurricane Center is similar this afternoon. They're expecting Irene to take a more central track through the Bahamas over the next 48 hours and make contact with the Outer Banks on Saturday afternoon, with a second landfall in New Jersey on Sunday afternoon. Again, it's critical to note that the errors in the track forecast 4 and 5 days out are quite large, and also that the consensus in the models over the past couple of days has been to nudge the track eastward, which can be seen in this track graphic archive.

Intensity forecast for Hurricane Irene
Despite the slight weakening that happened today, Irene is still expected to reach major hurricane status (category 3+) in the next 36 hours as it moves away from the Greater Antilles and into warm "open" water. The models tend to agree on a maximum intensity of category 3, however, the GFDL is the upper outlier, and is suggesting a category 4 on Friday. The intensity forecast from the National Hurricane Center is a wind speed increase to 125 mph (category 3) by Thursday. Irene will surely be a very intense hurricane by the time it nears the Mid-Atlantic.

Magnitude 5.8 earthquake rattles eastern U.S.

A relatively large and shallow earthquake struck the Mid-Atlantic just before 2pm EDT this afternoon, and shaking was felt up and down the east coast and as far west as Ohio. According to the United States Geological Survey (USGS), the epicenter was located 5 miles southwest of Mineral, Virginia, and was 3.7 miles deep—a very shallow earthquake. Buildings were evacuated all over the Mid-Atlantic, including the Pentagon, the White House, and NCEP, but have since been reopened. The National Cathedral in Washington D.C. was apparently significantly damaged in the earthquake. National Mall monuments and memorials have closed for the afternoon. Light aftershocks have been reported by people in the region, and the USGS has reported at least one aftershock (a 2.8 in magnitude).

Figure 2. "Did you feel it?" map from the USGS. Shaking reports from today's earthquake can be submitted to the USGS here.

This earthquake appears to be the strongest to occur in Virginia since May 31, 1897, when a magnitude 6 (approximately) struck Giles County. Reportedly, shaking was felt from Georgia to Pennsylvania and west to Indiana and Kentucky, which is an area that covers approximately 725,000 square miles. It's likely that this quake will have a similar extent when all the reports come in.


Earthquake Hurricane

The views of the author are his/her own and do not necessarily represent the position of The Weather Company or its parent, IBM.