Derecho threatens north east US with damaging winds

The US is no stranger to severe weather. You only have to look back at the last month, in which two deadly EF5 tornadoes (winds of more than 200mph) struck the state of Oklahoma, killing dozens of people and leaving a path of devastation.

With North America being such a large continental landmass, it straddles a huge range of climatic zones, from Arctic Canada, all the way down to sub-tropical Florida.

As a result of this, the type of weather that is experienced can vary massively in a short space of time. It can also be extreme, as big contrasts in temperature and humidity drive weather that can not only prove inconvenient, but deadly.

Thankfully, the US National Weather Service provides a comprehensive network of weather office across the country, monitoring what is happening and what is to come.

Part of this weather service incorporates the issuing of warnings for dangerous weather, such as severe thunderstorms, large hail, damaging winds and tornadoes. Maps are issued daily looking ahead for the next five days and highlight the areas most at risk.

During the next 48 hours, north eastern parts of the US look to be at moderate risk from severe weather as a relatively small, but active, area of low pressure moves eastwards.

The states most likely to be affected stretch from Illinois south of the Great Lakes, to New Jersey and Virginia on the east coast.

Potential hazards

At the moment, the main problem could come from severe thunderstorms that will have the potential to become rotating supercell thunderstorms – bringing the risk of spawning a few strong tornadoes.

In addition to wind damage from these severe thunderstorms, torrential rain and large hail will bring the risk of flash floods.

Derecho risk

Something that is also possible in the next 48 hours is a Derecho. This is a widespread, long-lived, straight line windstorm associated with a fast-moving band of severe thunderstorms.

They can travel hundreds of miles in a matter of hours, with sudden bands of damaging wind as strong as 80-100mph.

One such Derecho hit the north east US on 29 June last year, running from Illinois to Virginia – a similar path that of the severe weather expected in the coming days.

Peak wind gusts reached 80-100mph, killing 22 people, causing structural damage and leaving millions of people without power.

So whilst a Derecho doesn’t have wind speeds as high as a powerful tornado, they cover a larger area for much longer, thus affecting many more people.

As ever, I’ll keep you updated here on my blog and on Twitter – @liamdutton

Graphic courtesy of NOAA