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By: Dr. Jeff Masters , 4:17 PM GMT on September 07, 2005
The shear relaxed significantly over Ophelia in the past few hours, and she is now intensifying quickly. The hurricane hunters found a central pressure of 999 mb at 10:50am EDT, a 5 mb drop from seven hours ago. The peak winds of 40 kt (45 mph) on the northwest side are still not too impressive, but these will increase substantially in the next 12 hours, given what the pressure is doing and what I'm seeing on radar.
Long range radar out of Melbourne shows that convection is now starting to wrap all the way around the center, at a rate which is quite impressive. A closed center is likely later this afternoon. This will allow for more rapid intensification, and it now seems likely that Ophelia will be a Category 1 hurricane by tomorrow.
The satellite presentation of Ophelia shows a small storm, with good outflow to the north, and some improving outflow on the south side. The outflow to the north is joining and being aided by the outflow channel on the north side of Hurricane Nate. It will be interesting to see what happens to Ophelia's outflow when Nate scoots off to the northeast tomorrow; my guess is that there will be little effect.
Most of the action has been on the north side of Ophelia, as the northeast coast of Florida can attest to. Nearly three inches of rain has fallen along some coastal areas, from squalls that have rotated in from the ocean. Winds gusts at the St. Augustine pier were as high as 35 - 40 mph overnight. Sustained winds over the ocean areas off shore are 40 - 45 mph, and 12 foot seas have been observed. Large waves from Ophelia are already pounding northern Florida and the Carolinas. Given Ophelia's slow forecast track, this will be a major beach erosion event for these areas. As Ophelia "spins up", the outer rain bands have moved closer to the center of the storm and away from the coast, so Florida and Georgia will get a bit of a break from the rains the remainder of today. By tomorrow, the rains will probably again spread over these areas as Ophelia intensifies and expands in size.
Figure 1. Total rainfall from Ophelia as estimated by the Jacksonville Doppler radar.
The long term track and intensity forecast for Ophelia are highly uncertain. With the storm now intensifying more quickly than anticipated, the models are likely to have some quite different solutions later today. The computer model map has the appearance of a squashed spider, with each model taking Ophelia a different direction. The GFDL and BAMS Medium solutions take Ophelia westward across Florida and into the Gulf of Mexico almost immediately. These solutions are already incorrect, and are being discounted at this time. The Canadian model takes Ophelia out to sea behind Nate, but is the only model calling for this track. What I believe is the most likely scenario is one that is not promising for the U.S. This solution is the one favored by the GFS, UKMET, and NOGAPS models. These models forecast that steering currents over Ophelia will remain weak the next five days, which will allow her to remain over the warm ocean waters and gather strength. A weak trough of low pressure is forecast to move off the east coast Friday, which should act to push Ophelia away from the coast slightly. This trough could also create some shear and dump cold, dry air into the cyclone, weakening it temporarily. However, the GFS, UKMET, and NOGAPS models forecast that this trough will bypass Ophelia, and a ridge of high pressure will build back in forcing Ophelia westward or south-westward back toward the U.S. coast early next week. With so much time over warm water, and the shear likely to decrease once the trough bypasses her, Ophelia will have a good chance of attaining at least Category 2 hurricane status and making landfall somewhere on the Southeast U.S. coast. All interests along the Southeast coast from Miami to Cape Hatteras need to watch this storm.
Nate is a Category 1 hurricane with a large eye, and should intensify into a Category 2 hurricane by tomorrow. Nate is currently drifting slowly north, but is expected to accelerate norhteastward when the trough currently moving off of the East Coast picks it up tomorrow. This may spell trouble for Bermuda, which has already hoisted a Tropical Storm Warning and a Hurricane Watch.
Maria was briefly downgraded to a tropical storm, but is now back to a Category 1 hurricane. She is expected to turn into a large and powerful extratropical storm by tomorrow and bring high winds and heavy rain to Iceland on Saturday.
The rest of the tropics
An upper-level low pressure system is over the western Gulf of Mexico and is generating some showers there. There is now some surface low pressure developing underneath, but tropical development in this type of system happens very slowly, and usually not at all.
A large tropical wave with spin just moved off the coast of Africa near 9N, and will have to be watched as it moves westward this week.
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