US weather: ‘Witch storm’ threatens to bring Thanksgiving tornado chaos
US weather: ‘Witch storm’ threatens to bring Thanksgiving tornado chaos
The weather channel
A vicious ‘witch storm’ whipped up by tropical winds from the Gulf of Mexico hitting Arctic air over the United States threatens Thanksgiving getaway tornado chaos.
A huge cyclonic low-pressure system sweeping America has sparked warnings for travel chaos and flight disruption through the next 24 hours.
Colliding warm and cold air masses driving atmospheric instability threaten torrential rain, wind, thunder and powerful twisters – a so-called ‘witch storm’.
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Volatile weather conditions are expected to settle down after today as the storm forges eastwards towards the Florida coast and out into the Atlantic.
Jim Dale, US weather correspondent and senior meteorologist for British Weather Services, said: “We are going to remain in tornado territory through Wednesday before the weather calms down for Thanksgiving itself.
“This is because warm and cold air masses are mixing, and this is always going to bring instability and the threat of thunderstorms, tornadoes, wind and rain.
“By Thursday, the risk will have moved eastwards leaving benign Thanksgiving.
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Witch storms form when cold air mixes with warm air
The Weather Channel
“However, the risk of disruption will remain during the getaway period.”
The storm has been fuelled by a blast of tropical warmth from the Gulf of Mexico crashing into colder air from the Arctic.
Northern States have seen temperatures drop over the past week while further south the mercury has been rising.
Cold and warm air provides a volatile cocktail to drive powerful weather systems, including tornadoes in prone regions.
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The Weather Channel
It provides the perfect ingredients to spawn ‘witch storms’ – peculiar to autumn when hot and cold air masses mix to produce strong low-pressure systems.
The name refers to the ‘Witches of November’, a phrase used to describe unusually powerful storms which often target the Midwest during October and November.
Weather Channel meteorologist Chris Dolce said: “This isn't some reference to Halloween being carried over into the new month.
“Winds from these storms often cause tree damage and power outages, and they are also a major hazard for shipping on the Great Lakes.
“They develop in [autumn] due to increasing temperature contrasts from north to south across the country helping to produce stronger low-pressure systems.
“The stronger they are, the more intense winds they can produce.”
The added risk of thunderstorms today could lead to violent electrical outbursts and heavy downpours.
Linda Lam, senior meteorologist for The Weather Company, said: “A low-pressure system will be tracking across the south and into the east for the first half of this week.
“Moisture from the Gulf of Mexico will surge northward ahead of the cold front associated with this system, increasing instability in the atmosphere.
“Damaging winds and a few tornadoes are the main concern.
“Locally heavy rain may lead to some flash flooding, but overall, the rain will be welcome.”
Holiday-makers can look forward to a calmer Thanksgiving with the witch storm expected to fly off into the Atlantic ahead of the weekend.