Saturday, October 14, 2017

Hurricane Ophelia Looks Set To Smash Into Ireland

Here is this morning's track forecast from Wunderground:

If accurate, the storm will bisect the entire island—southwest to northeast—as a category 1 hurricane.
Here's some background from Weather Underground's Cat 6 blog, we'll be back with more later today.

Category 2 Hurricane Ophelia Headed Towards the Azores and Ireland
Category 2 Hurricane Ophelia was headed east-northeast at 12 mph late Friday morning towards the Azores Islands, and is likely to bring tropical storm-force winds and heavy rains to the Azores on Saturday, and to Ireland on Monday. Ophelia continued to look impressive on satellite imagery on Friday afternoon, with a distinct eye surrounded by a moderately intense area of heavy thunderstorms. Ophelia had favorable conditions to maintain hurricane strength, with moderate wind shear near 15 knots and sea surface temperatures (SSTs) a marginally warm 26°C (79°F)--about 1°C above average for mid-October.
Ophelia’s impact on the Azores
Ophelia will become caught in the prevailing westerlies this weekend, which will accelerate the storm to the east-northeast and then northeast. Sea surface temperatures will gradually drop and wind shear will rise on Saturday and Sunday, weakening the storm. However, Ophelia will begin to derive energy from non-tropical (baroclinic) processes this weekend, and should be able to maintain Category 1 strength until Monday, when it is expected to transition into a powerful post-tropical (mid-latitude) storm with winds of hurricane strength.
On Ophelia's expected course, the storm will track just south of Santa Maria, the southeastern-most island of the Azores, on Saturday night. The 12Z Friday run of the GFS model brings Ophelia within about 60 miles of Santa Maria. This track would put the island on the weaker left-hand side of Ophelia, where maximum sustained winds of 40 – 50 mph will be likely. 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 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.
Ophelia’s impact on Ireland
Ophelia is expected to complete the transition to an extratropical storm just off southwest Ireland on Monday morning. As this process unfolds, the wind field of Ophelia will expand, and Ophelia promises to be a damaging wind event for Ireland. Expect widespread tree damage and uprooted trees, damaged roofs, power blackouts, mobile phone coverage interruptions, and flying debris. The Irish weather service has issued a Yellow Alert for Monday.

Winds will begin to strengthen in Ireland on Monday morning, but the real impact will be Monday afternoon and evening. Expect sustained southeasterly winds of 55 – 65 kph (34 – 40 mph) for coastal southwest Ireland (Munster province) and southeast Ireland (Leinster province.) Along the south Munster coast (south Cork and south Waterford), sustained winds of 65 - 75 kph (40 – 46 mph) are likely, and winds could be higher along exposed headlands and over the Wicklow Mountains. Up to 2” of rain can be expected over higher terrain from Ophelia. One concern for Ophelia’s impact on Ireland may be the potential for the ex-hurricane to develop a “sting jet.” This is a current of extra-strong jet stream winds that start out about 3 – 4 km above the surface, then descend over a 3 – 4 hour period. Rain falling into the jet evaporates and cools, causing the winds in the sting jet to accelerate as they reach the ground....MORE
Cat 6 goes on to discuss some notable Irish and U.K. storms. including the ‘Great Storm’ of 1987 which exacerbated the U.S. market crash of October 19, 1987. We'll have more on that as well.