Olga pounds Puerto Rico; major 'Noreaster coming Sunday

The hurricane season of 2007 is definitely not over! Subtropical Storm Olga is the 17th December named storm to develop in the Atlantic since record keeping began in 1851, and only the fourth December named storm to hit land (Figure 1). Seven of the 17 December storms have occurred since 1995. Eight of the December storms have been hurricanes, with a Category 2 hurricane in 1925 being the only December storm to hit the mainland U.S.


Figure 1. Tracks of all Atlantic named storms that have formed in December.

As seen on visible satellite loops, the heavy thunderstorm activity associated with Olga is displaced 100-200 miles to the north of the center. This is one of the hallmarks of a subtropical storm. The difference is not important, as the winds and rain are similar for both types of storms. Long range radar out of Puerto Rico clearly shows the circulation of Olga and some well-organized bands of rain. Rain is the major threat from Olga, and amounts of 3-6 inches have already fallen over northern Puerto Rico, causing flash flooding and mudslides. Heavier rain amounts of over eight inches have fallen on ocean areas to the north of Puerto Rico (Figure 2), and rainfall amounts of up to 10 inches may hit the regions of the Dominican Republic hard hit by Tropical Storm Noel just six week ago. Haiti is also at risk of heavy rains that might cause life-threatening flash floods and mud slides.


Figure 2. Latest precipitation estimate from the Puerto Rico radar.

Wind shear, which dropped to about 15-20 knots Monday evening, has increased to 20-30 knots today. This higher shear, combined with Olga's passage over the rough terrain of Hispaniola, should be enough to tear the storm apart. The remnants of Olga may still bring heavy rains of 2-4 inches to Jamaica and eastern Cuba Wednesday and Thursday. None of the computer models foresee that Olga will survive to become a tropical storm in the Western Caribbean. The Hurricane Hunters are not on call to fly Olga.

Major 'Noreaster coming Sunday
Both the GFS and ECMWF models are forecasting that a major winter storm will track across the Ohio Valley on Saturday, then explode into a powerful 'Noreaster on Sunday with a central pressure of 970-980 mb off the U.S. northeast coast. Heavy snow amounts of 1-2 feet and significant ice accumulations are possible in inland regions of the Northeast. Locations nearer the coast, such a Philadelphia, New York City, and Boston may mostly get rain, but it is too early to be confident of this forecast. Minor to moderate coastal flooding is possible along the coast from New York City to Maine on Sunday.

I'll have a update Wednesday morning.

Jeff Masters