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| Ophelia Gathering Strength in Central Atlantic (1469318) | |||
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Ophelia Gathering Strength in Central Atlantic |
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Posted by DANd124 on Tue Oct 10 19:19:44 2017, in response to OPHELIA: ITS BUSH'S FAULT!, posted by Mitch45 on Wed Sep 14 15:01:49 2005. https://www.wunderground.com/cat6/ophelia-gathering-strength-central-atlanticTropical Storm Ophelia appears to have its sights set on becoming the tenth consecutive hurricane of this year’s Atlantic season. As of 11 am CDT Tuesday, Ophelia’s top sustained winds were 50 mph. Fortunately, Ophelia is in the middle of the North Atlantic, far from land and about 780 miles west-southwest of the Azores. Ophelia was looking much more symmetric in satellite imagery on Tuesday morning, after days of strong shear that gave Ophelia’s showers and thunderstorms (convection) a lopsided structure. The convection was not particularly strong, which fits with the “cold” environment surrounding Ophelia. Sea surface temperatures are barely warm enough for development—only 26-27°C, or 79-81°F. However, this is substantially above average for the time of year (1-2°C), and the upper atmosphere is unusually cold, so the combination of the two is boosting instability. Outlook for Ophelia Computer models have come into very strong agreement that Ophelia will soon be a hurricane. Nearly all of the 70 ensemble members of the GFS and European model runs from 00Z Tuesday bring Ophelia to hurricane strength, as do the 12Z Tuesday SHIPS model and the 06Z Tuesday runs of the HWRF and HMON intensity models. Wind shear over Ophelia has dropped into the light to moderate range (around 10 knots), and SHIPS now predicts that shear will remain mostly below 15 knots through Saturday. The atmosphere around Ophelia will remain on the dry side (mid-level relative humidity around 50%), so periods of dry-air intrusion could chip away at Ophelia’s intensity. In its 11 am EDT Tuesday advisory, NHC predicted that Ophelia would become a hurricane by Thursday morning. Light steering currents are expected to keep Ophelia drifting southeast for the next day or two, before stronger upper-level westerlies kick in. By Saturday, Ophelia is likely to be accelerating east-northeast just south of the Azores; although a direct hit appears unlikely, it’s too soon to rule out that possibility. In NOAA’s historical hurricane database, which extends back to 1851, only 11 hurricanes have passed within about 200 miles of the Azores (as noted by weather.com). Every one of those occurred in August or September—except for strikingly unseasonal Hurricane Alex, which struck the islands in January 2016 just after weakening to tropical-storm strength. Looking further ahead, NHC is predicting Ophelia to transition into a post-tropical cyclone with hurricane-force winds by Saturday as it continues racing east-northeast toward the Iberian Peninsula. Only two storms are known to have struck the west coast of Portugal or Spain as tropical cyclones: a transitioning hurricane in October 1842 and Hurricane Vince (as a tropical depression) in October 2005. Intriguingly, phase-space diagrams from Florida State University based on the 06Z Tuesday run of the GFS model suggest that Ophelia might actually approach the Iberian Peninsula as a weakening warm-core tropical cyclone—i.e., a tropical storm. Ensemble models show a slight chance of Atlantic development this week in two areas of disturbed weather, one north of the Leeward Islands and the other in the central tropical Atlantic. Given the unfavorable state of the Madden-Julian Oscillation (see below), development of either disturbance appears quite unlikely, and neither was highlighted in the tropical weather outlook issued by NOAA at 8 AM EDT Tuesday. |
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