Fiona heads to Canada as threat to US grows from further disruption

Fiona heads to Canada as threat to US grows from further disruption

Hurricane Fiona intensified into a Category 4 powerhouse during the predawn hours Wednesday, a day after it became the first major hurricane of the 2022 Atlantic season. It hit Puerto Rico during the weekend with catastrophic rains and violent to destructive winds, cutting off power to the entire territory before hitting the Dominican Republic and sweeping the Turks and Caicos Islands.

Now the system is poised to pass near Bermuda as a high-end storm before charging into the Canadian Maritimes, lashing Nova Scotia with winds of up to 100 mph. By then it may no longer be tropical, but it could be as strong as a high-end Category 1 or low-end Category 2 hurricane.

It comes amid a sudden awakening of tropical storm activity in the Atlantic. Tropical Storm Gaston developed west of the Azores on Tuesday, and two other tropical waves in the eastern Atlantic are of interest.

The disturbance of most concern, however, is just east of the Windward Islands. This should cross the Lesser Antilles, reach the Caribbean later this week and enter an environment extremely favorable for intensification. The chances of a hurricane entering the Gulf of Mexico are increasing, and Gulf Coast residents, including the United States, should be on the lookout.

At least four dead in Puerto Rico during Hurricane Fiona, FEMA says

The sudden surge in tropical Atlantic activity comes just a week after the climatological peak of hurricane season, meaning it is on schedule. August was the first since 1997 not to feature a single named storm developing anywhere in the basin, but next week could reinforce the adage that it only takes one storm to kill. calm season becomes catastrophic.

By mid-morning Wednesday, Fiona was a Category 4 hurricane with sustained eyewall winds up to 130 mph. It was moving due north at 8 mph about 700 miles southwest of Bermuda. The British Overseas Territory has been placed under a tropical storm warning and a hurricane watch, the latter in case Fiona’s projected path comes closer to the island.

During a recent reconnaissance flight, a Hurricane Hunter aircraft encountered winds of 144 mph at 8,530 feet in the eyewall. This sustains surface winds of around 130 mph.

The infrared satellite revealed a mature eye and cloud top temperatures of minus-112 degrees Fahrenheit, indicating clouds rising about 50,000 feet high. It looks like Fiona may push out some dry air from the north and west.

Hurricane hunters also found a spike of around 14 or 15 degrees in air temperature in the eye. It is a sign of intensity. Air rises in the eyewall and sinks in the eye, sinking, warming, drying, and creating a void of cloud cover. This is why the eyes of the most powerful hurricanes are often the hottest and sometimes sunny.

Transition to Canadian Superstorm

Fiona is expected to pass west of Bermuda Thursday evening or Friday morning. The island will likely experience tropical storm conditions, or winds of 39 mph or more, along with heavy downpours in the outer rain bands. Thereafter, it will continue north while being pulled west by an approaching mid-latitude low pressure system.

As Fiona approaches the Canadian Maritimes, it will begin to draw on the energy of the jet stream, converting into an “extratropical” or non-tropical depression. It’s unclear if Fiona will still retain her tropical features as she lands in Canada early on Saturday. Either way, wind gusts of 100 mph or more are likely.

The exacerbation of the winds will be a “pressure dipole”, or the juxtaposition of an intense anticyclonic system south of Greenland. The proximity of two extreme systems – one a low pressure storm and the other a hot high pressure dome – will amplify the winds due to the extreme pressure gradient or change in atmospheric pressure with distance.

There are signs that Fiona could erase minimum air pressure records for September and potentially for all recorded months in Nova Scotia. The lowest atmospheric pressure recorded there was 950.5 millibars. (Typical air pressure at sea level is about 1,015 millibars; any deficit represents “missing” air that has a vacuum effect, resulting in strong winds.) Models suggest Fiona may have an atmospheric pressure of about 930 millibars. Hurricane Sandy in 2012 was around 940 millibars when it hit New Jersey.

In addition to extreme winds, a storm surge of 5 to 8 feet would be possible, as well as offshore waves 80 feet high. Extremely dangerous conditions will result for sailors.

Also in the Atlantic, tropical storm Gaston has just been created. It lies 775 miles west of the Azores and has winds of 65 mph.

In satellite imagery, Gaston’s convection, or thunderstorm and shower activity, was not as robust as it was 24 hours ago. It may also begin to acquire non-tropical characteristics; the band of stormy arcs east of the center suggests the formation of a cold front. True tropical systems have no fronts.

The storm will slowly meander northeast over the next few days, potentially bringing strong winds to the Azores this weekend before weakening and drifting west.

A developing gulf, a Caribbean threat

There are three other areas to watch in the Atlantic. One is over the Eastern Central Atlantic and has a low to medium probability of long-term development, but near-term strengthening is unlikely at this time. There is another tropical wave over Senegal that may begin to develop as it moves off the African coast in the coming days.

Then there is a third system near the Windward Islands. This is one that could be a big problem.

In the next few days it will cross the Lesser Antilles with wind and rain, but shear – or a disruptive change in wind speed and/or direction with height – will prevent its further development until the end. from this week. This shear comes from the exit, or high altitude exhaust, exiting Fiona well to the north.

But by Sunday or Monday, the shear will ease. The system, baptized 98L, will find itself in an extremely favorable environment characterized by sea water close to 90 degrees. This means that the Caribbean is full of untapped “ocean heat content” or fuel to sustain an intense cyclone. The shear will be low and the high pressure at altitude will help the fan exhaust the 98L air. This evacuation of “spent” air will allow the incipient storm to more easily inhale warm, moist air in contact with the ocean from below. This will promote intensification.

From here, it’s impossible to know exactly when the storm will begin to curve northward. Cuba or the Yucatán Peninsula could be in play, or the storm could roar directly into the Gulf of Mexico.

One thing is certain: putting on a developing storm in the Caribbean with low shear and warm water temperatures in September is like lighting fireworks inside a tent. You don’t know exactly which direction the firework will go, but once the wick is lit, something is going to be hit.

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