Ophelia appears to have nearly completed the process to Post-Tropical based on satellite imagery, with the whole arrangement of frontal boundaries and more asymmetric wind field and lack of any significant tropical characteristics outside of some convection (thunderstorm activity) northeast of the center. Ophelia is still a hurricane-force cyclone (likely top sustained winds 75-85 mph) and impacts still expected to quickly increase over Ireland Monday morning with rain, damaging winds and dangerous surf and coastal flooding.
Hurricane Ophelia…at least it was still considered one at 11 am AST…is quickly transitioning to a hybrid post-tropical cyclone. I made up a schematic using current infrared satellite imagery. You can clearly see the transitioning hurricane becoming surrounded by cold, dry air on its’ back side, with its own warm, moist tropical air mass contributing to warm air advection ahead of it. And you can the developing frontal structure…cold front developing offshore Portugal and warm frontal cloud structure fanning out far to the north of the low center and offshore Ireland. The cyclone itself should be fully post-tropical in the next few hours, if it can’t be considered so already. Impacts (moderate to heavy rain and damaging winds) begin their arrival Monday morning. My forecast for Ireland (written last night) can be found HERE.
Hurricane Ophelia set two records: 1) The highest latitude major hurricane on record in the North Atlantic Basin, set beginning at 35.9 N and 2) the most easterly major hurricane on record in the basin, set beginning at 26.6W. It will likely weaken below major hurricane force by Sunday morning as it begins to undergo transition into a frontal cyclone from its interaction with the jet stream and further reduction of sea surface temperatures below 72 degrees F/22 degrees C. However, it will be one for the record books.
Fortunately, Ireland and the United Kingdom will not need to worry about a major hurricane hitting them. They will need to worry about a likely damaging windstorm from a post-tropical hybrid cyclone. The post-tropical incarnation will develop frontal characteristics as it initially weakens, but its strong inner warm-core will continue to release some heat into the system, re-intensifying it as it becomes fully embedded in the mid-latitude westerlies and races into Ireland and the UK Monday afternoon and evening. My updated forecast for Ireland is below. Still expecting winds capable of downing trees and causing major power disruptions. The forecast for intense winds is high in confidence as computer models hone in on the center of the storm either coming ashore the southern tip of Ireland or just grazing the western shore. This is favorable for a “big blow” over the entire island. Residents need to be prepared to stay indoors and stay safe during the day Monday.
Ireland Forecast for Post-Tropical Cyclone Ophelia:
Monday Morning (After 7 am local time): For the southern half of the island, wind gusts of 40-50 mph (64-80 km/h) will develop during the morning, increasing to 60-85 mph (97-137 km/h) by mid to late morning from the coast, northward. The strongest gusts will be along the coastal areas, especially the south shores where isolated gusts may approach 100 mph (161 km/h). For the northern half of the island, wind gusts to 40 mph will develop mid morning , increasing to 50-60 mph late morning, from south to north.
Monday Afternoon (After noon): For the south, wind gusts of 60-85 mph (97-137 km/h) early afternoon with isolated to 100 mph/161 km/h along the south/southeast shores). For the north, wind gusts of 50-60 mph (80-97 km/h) early afternoon will increase to 60-85 mph by mid afternoon with isolated gusts to 100 mph along the northeast shores, spreading from south to north into the late afternoon.
Monday Night (after 5 pm local time): For the south, wind gusts will gradually decrease to 40-55 mph (64-89 km/h) during the early evening from south to north. For the north, wind gusts will gradually decrease to 40-55 mph during the mid to late evening (after 7 pm) from south to north.
Sea conditions will be hazardous all around Ireland with wind gusts in excess of 100 mph (161 km/h) likely in the south coastal waters and in the Irish Sea.
Hurricane Ophelia has strengthened into a Category 3 hurricane with maximum sustained winds of 115 mph as it moves south of the Azores. It is moving over prime atmospheric conditions, even as it overcomes waters of only 25 degrees C/77 degrees F. In normal tropical environments, tropical cyclones need water temperatures of 26 degrees C/79 degrees F to maintain themselves and warmer to significantly strengthen. However, the colder temperatures in the upper-atmosphere associated with the mid-latitude troposphere is providing Ophelia with ample atmospheric instability (warm, moist air rising into cold air aloft intensifying thunderstorm activity). In addition, mid-latitude dynamics are playing a role…the approaching frontal system and associated upper-level trough of low pressure approaching Ophelia is giving the system a “poleward outflow jet” to pull air away from the system and allow the surface low to strengthen.
See my previous post from late last night for my wind forecast for Ireland. Strong winds should begin to impact the island midday Monday (local time), with stormy conditions lasting into Monday night. The southeastern Azores will see some gusty winds and 1-3 inches of rain as it passes by this evening and night.
Hurricane Ophelia is a high-latitude hurricane by tropical standards…a Category 2 storm with maximum sustained winds of 100 mph as of 11 pm AST…moving south of Azores at 20 mph.
This hurricane, is on track to take its already unusual path northward toward a collision course with Ireland and the United Kingdom Monday and Tuesday!
Not to worry, however. Ophelia will NOT be a tropical cyclone when it arrives in the British Isles Monday. Sunday, the hurricane will begin to pass over much cooler waters between the Azores and Portugal (and note, the hurricane is currently over waters 2-3 degrees C/~3.5-5.5 degrees F above normal). At the same time, if you look at the previous satellite analysis, the hurricane will begin to interact with the existing frontal zone and ingest air from an approaching cold air mass moving in from the North Atlantic. This will begin the process of extratropcial transition where Ophelia becomes a mid-latitude frontal system. However, because of its old, warm tropical air mass, it will continue to retain some of its internal energy, enabling it to be a powerful hurricane-force windstorm.
I have moderate confidence in my forecast…some uncertainty deals with the track of the low pressure system. A track farther offshore to the west would limit significant winds to the south and west shores and coastal communities. A track very close or even onshore the south coast would send very high winds deeper inland into Ireland. Regardless, those in the country should expect widespread downed trees, power outages, and difficult driving conditions for high-profile vehicles during the afternoon into late evening Monday.
Here is the climatological history of all known tropical cyclones in the North Atlantic just to show the rarity of systems such as Ophelia. Although some cyclones may have been missed prior to the satellite area, it is possible that such cyclones were less likely to survive in the distant past because of cooler waters where Ophelia is located now. Sea surface temperatures have warmed on Earth because of climate change.