Ophelia, and 3 new threats

Ophelia
Yesterday, I was trying to imagine a day when I wouldn't talk about Ophelia moving slowly. Today is not the day :-( since Ophelia was still stalled out near Cape Hatteras this morning. However, the past few hours the Norfolk long range radar loop has shown a dramatic increase in Ophelia's forward speed and turn to the north-northeast. There is hope, then--tomorrow I will not have to talk about Ophelia moving slowly! I expect that the trough giving me a rainy day here in Michigan has now nabbed Ophelia and will swing her up the East Coast at a respectable speed today and tomorrow. Ophelia will still generate some trouble on her trek north; expect a 1 - 3 foot storm surge for southeast Massachusetts and Nova Scotia, 1 - 3 inches of rain, and sustained winds up to 40 mph as Ophelia brushes by.

While Ophelia did dump it share of heavy rain--around 5 - 7 inches near Wilmington, and over 10 inches around Cape Fear, south of Wilmington--the rain was mostly confined to the coast, and did not cause widespread flooding problems. Ophelia's winds also did relatively light damage--sustained hurricane force winds (74 mph) were only observed at one location, on Cape Lookout near the Outer Banks. The highest wind gusts measured were 92 mph on Cape Lookout and 83 mph at Cape Hatteras. The storm surge was what caused the main havoc with Ophelia--surges heights of up to 10 - 12 feet were observed along the Neuse River north of Wilmington. Preliminary damage estimates put Ophelia's damage to North Carolina over $10 million, but less than $100 million.


Figure 1. Estimated rainfall from the Morehead City radar for Ophelia's passage.

Wave nearing the Windward Islands
A well-organized tropical wave 600 miles east-southeast of the Windward Islands has the potential to develop into a tropical depression in the next few days. The wave's surface circulation is better defined today, and is visible on both satellite imagery and QuikSCAT satellite measurements. Deep convection is limited, but has increased since yesterday. The wave, now located near 10N 50W, has moved away from the equator some, and has a better chance for development as it continues to gain latitude while moving west-northwest at 15 mph. Wind shear has decreased to about 10 knots, and the upper-level winds appear favorable--a small upper-level anticyclone is over the wave, and should provide good outflow if more deep convection starts to fire up.

The early track models are split, withe GFDL disippating the system immediately and the BAMM taking it into the Caribbean. The BAMM solution is radically different from the one six hours ago, which showed the large mid-Atlantic trough turning the system northwestward and missing the Leeward Islands. I expect the new BAMM solution is correct; the system is too shallow and too far south to get caught up by the mid-Atlantic trough, and will cross into the Eastern Carribean Monday. I suspect that the system will organize too slowly to pose a hurricane threat to the Leeward or Windward Islands. Hurricane Emily took a very similar path to this disturbance and developed into a hurricane right when it crossed the Windward Islands into the Caribbean, but was already a tropical storm when it reached 50W longitude, where our disturbance is today.


Figure 1. Early track model runs for the disturbance approaching the Windward Islands.

Blob northeast of Puerto Rico
A concentrated area of thunderstorms northeast of Puerto Rico has developed in the base of a large trough of low pressure. This disturbance will separate from the trough and move westward towards the Bahama Islands the next few days. Strong upper level winds out of the west are creating about 15 knots of shear over the disturbance, down from 20 knots yesterday. The shear should continue to drop the next few days, and may be low enough by Sunday to allow a tropical depression to form. The system should be in the Bahama Islands by then, and could threaten South Florida and Cuba as it continues to track west. Several computer models indicate that the disturbance is more likely to develop once it reaches the Gulf of Mexico, and pose the greatest threat to Mexico or Texas. There are no early computer model track points for this disturbance yet, I will post them when they become available.

ITCZ
The Intertropical Convergence Zone (ITCZ), the band of strong thuderstorms between Africa and South America, has historically been the source of many of the severe hurricanes that affect us in September. These "Cape Verde" type storms, so named because they originate from disturbances in the ITCZ near the Cape Verde Islands, have yet to make an appearance during this peak time of hurricane season. The ITCZ has become very active the past few days, and is forecast to continue to remain active the next two weeks. I expect at least one major Cape Verdes type hurricane to form by the end of September.

One candidate might be an area of distubed weather near 9N 36W. The QuikSCAT satellite shows a surface circulation here, and we'll have to watch this disturbance as it tracks westward the next few days.

Jeff Masters