Hurricane Irene Slightly Weaker, Hurricane Warnings Issued for U.S. East Coast

Posted on August 26, 2011

Hurricane Irene 3 Day Cone August 26 5 Am

The National Hurricane Center (NHC) continues to forecast Hurricane Ike to impact the North Carolina coast (particularly the Outer Banks) and then continue up the coast where it will likely deliver a severe blow to the Mid-Atlantic and New England regions. Hurricane warnings have been extended along the U.S. east coast. Hurricane warnings run from the coast of North Carolina to Sandy Hook, New Jersey. Hurricane watches run from Long Island into New England. You can see a larger image of the above graphic here.

Hurricane Ike has maximum sustained winds of 110 mph. It is moving north at 14 mph and has a minimum pressure of 942 mb. This is the lowest minimum pressure for Ike in its lifetime (see chart), but the winds have still dropped slightly to 110 mph despite the low pressure.

In its latest discussion the NHC notes that some wind shear is helping to prevent the hurricane from strengthening. However, the pressure has been continuing to drop (strengthen) and the NHC is still calling for the possibility of modest strengthening.

WATER VAPOR IMAGERY AND ANALSYES FROM CIMSS AT THE UNIVERSITY OF WISCONSIN SUGGEST THAT IRENE IS ENCOUNTERING LIGHT TO MODERATE SOUTHWESTERLY VERTICAL WIND SHEAR. THIS...ALONG WITH THE CURRENT CYCLONE STRUCTURE AND DRY AIR ADVECTING TOWARD THE HURRICANE IN WATER VAPOR IMAGERY...ARGUE AGAINST SIGNIFICANT STRENGTHENING.... AND INDEED THE INTENSITY GUIDANCE SHOWS LITTLE CHANGE IN STRENGTH BEFORE LANDFALL. ON THE OTHER HAND...THE EYEWALL CONVECTION IS CURRENTLY STRONG...AND THE SEA SURFACE TEMPERATURES ALONG THE FORECAST TRACK ARE 28-29C. THIS SUGGESTS SOME MODEST STRENGTHENING IS POSSIBLE.

Hurricane Irene is a very large hurricane so it has the potential to deliver a surge larger than that of a typical category 2 hurricane. Hurricane Ike (2008) is a good storm to reference here. Ike made landfall as a category 2 in Galveston, Texas with winds of 110 mph and a central pressure of 950 mb. Despite being a category 2, Ike delivered a higher level surge because its wind field was so huge. There is a new hurricane scale being considered that rates hurricanes based on its size and wind field and not just the maximum speed of its winds.

Image: NOAA


More from Science Space & Robots