CHICAGO, Aug. 18, 2008 - Impact Forecasting, LLC, a unit of Aon Corporation (NYSE: AOC), released the following alert Aug. 18 at 10:35 a.m. CDT regarding Tropical Storm Fay and Typhoon Nuri. For more information, or to subscribe to Impact Forecasting's weekly Cat Alerts and get breaking news about global meteorological events, visit http://aon.mediaroom.com/index.php?s=63&item=261.

The center of Fay has moved into the Florida Straits this morning.  Satellite imagery and radar data show large clusters of thunderstorms banding over the eastern side of the system, but little activity on the western side.  This asymmetry is likely due to wind shear and dry air filtering into the storm.  An Air Force Hurricane Hunter aircraft is currently flying through Fay and recently located winds at the surface approaching 60 mph (95 kph).  Based on this data and similar Doppler radar estimates, the initial intensity is increased to 60 mph (95 kph).  The latest minimum pressure reported by the hurricane hunter is 1003 millibars.

Fay has been moving erratically for the past couple of days, with the center currently moving faster toward the north-northwest.  The initial motion is towards the north-northwest.  Fay is entering a weakness in the ridge of high pressure over the eastern Gulf of Mexico and Florida.  An upper level frontal boundary which is moving through the southeastern United States is the reason for the erosion of the ridge.  Beyond 36 to 48 hours, the front is forecast to lift out and allow another dome of high pressure to build over the eastern United States ahead of a second frontal boundary over the western Gulf Coast states.  Most of the forecast computer models agree on this evolution by forecasting Fay to move generally northward near or over the Florida Peninsula and into the eastern United States. 

However, some models forecast Fay to turn northeastward into the Atlantic and stall in five days.  Other models continue to call for a more westerly motion toward the Florida Panhandle, though those scenarios are becoming less likely.  The new official forecast track from the National Hurricane Center follows a northward scenario, just a little to the east of the general consensus of most computer models.  The track brings the center over the southwestern coast of Florida within a 24 hour window. 
 

Fay is currently in a moderate wind shear environment, and the upper-level winds will likely remain less than ideal for continued development over the next 24 to 48 hours.  This reasoning (combined with the dry air and the current structure) will likely prevent rapid intensification.  However, gradual strengthening is still likely prior to landfall.  The official intensity forecast from the NHC calls for Fay to become a minimal hurricane by landfall.  After landfall, Fay should slowly weaken and become a remnant low after five days.  There is low confidence in the intensity forecast, and there is a distinct chance Fay might not reach hurricane strength before landfall - especially if it moves to the right of the forecast track. 
 

It should be noted that - similar to Charley in 2004 - small deviations from the forecast track could make large differences in when and where the center of Fay makes landfall.

Storm tides of 3 to 5 feet above normal are possible along the southwestern coast of Florida near the center of Fay.  Tides of 2 to 4 feet above normal are possible in the Florida Keys. 
 

Fay is expected to produce total rainfall accumulations of 4 to 8 inches over much of Cuba, with isolated maximum amounts of 12 inches.  These rains could produce life-threatening flash floods and mud slides.  Heavy rains are also expected to spread across South Florida today.  Storm total amounts of 4 to 8 inches, with maximum amounts of 10 inches are possible for the Florida Keys and South Florida.  Rainfall accumulations of 3 to 5 inches are possible in the northwestern Bahamas.
Isolated tornadoes are possible today over the Florida Keys and the southern Florida Peninsula.

Typhoon Nuri, located approximately 981 kilometers (610 miles) east-northeast of Manila, Philippines, is currently tracking west at 27 kph (17 mph).  Nuri developed as a tropical depression on late Saturday with sustained winds of 50 kph (30 mph).  Nuri gradually strengthened during the day on Sunday as it headed slightly north of west, becoming a tropical storm Sunday morning.  During the day on Sunday, Nuri started a due west trek while continuing to strengthen.  This morning, Nuri achieved typhoon status while taking a slightly north of due west path.

The system continues to strengthen due to improved thunderstorm consolidation, tightly-curved thunderstorm banding and a defined eye feature on satellite.  Animated satellite imagery shows a strengthening high pressure cell over the center providing improved outflow, particularly over the east and southeast quadrants.  Outflow on the northern side has remained weak but has not prevented the system from intensifying over the past 24 hours.  Nuri is tracking westward under the influence of a ridge of high pressure positioned north of the system.  
 

The system is forecast to remain on a westward course due to the strong high pressure ridge.  The computer models are expecting this ridge to continue through the next 48 to 72 hours.  During this time, Nuri is forecast to rapidly intensify through the next 36 hours due to warm sea surface temperatures and no land disruption.  However, further significant intensification will be unlikely after that time period due to land interaction, though the intensity at that time will likely only slow or simply be maintained.  After this time, there is a large degree of uncertainty in the extended forecast due to the weakening of the ridge of high pressure.  Most of the models indicate recurvature west of Taiwan with the ridge depicted stronger and maintaining longer north of the system.  It is possible that Nuri will track on a more west-northwestward track than the current forecast reflects.

Media Contact: Rahsaan Johnson, 312.381.2684, rahsaan_johnson@aon.com