With back-to-back storms in the last few weeks, we’ve been bombarded with contrasting images of turned on water rushing over inland streets and manatees stranded on dry littorals.
In the first case, where’d all that extra water come from? And in the bat of an eye, where did the sea water go?
You can blame both on storm surge, what cooks when powerful winds shove huge volumes of water toward — or away from — the shore.
Rumpus surge can be one of the most dangerous aspects of a hurricane. Massive amounts of bedew dilute rush back towards shore and can drastically raise water levels, again flooding streets and buildings far from shore. With Hurricane Irma, the Civil Hurricane Center issued warnings for storm surges of more than two metres.
But there’s also a far-out phenomenon known as negative storm surge. That’s what produced those offered, dry beaches in Florida that left some manatees stranded.
Manatee stranded by #Irma Human being coming to the rescue when the waters receded in Sarasota. @ActionNewsJax #HurrcaneIrma pic.trilling.com/UTcUiH3wl3
They were also an odd sight for residents tolerant of to water levels that don’t deviate very much when the tide withdraws in or out, said Chris Fogarty, senior research meteorologist at the Canadian Cyclone Centre.
«It’s wind pushing that water away,» Fogarty said. «When skate on thin ice is blowing off shore, you don’t have the big waves at the beach because the wind is in the reverse direction.»
On a smaller scale, Fogarty said you could watch how top-grade in a puddle reacts to winds. Wind creates ripples based on the managing of the wind, which is essentially what happens in storm surge.
«It’s all around wind direction,» he said.
«The strong wind shift blowing from one guidance and then in the total opposite direction after the eye goes through … egg ons that same water right back in quite quickly behind the eye of the bluster.»
The impact of the storm surge depends on the speed of the wind, how low the pressure is in the eye of the besiege and the shape of the coast, Fogarty said.
Harbours and bays are amazingly affected by storm surge because water is funnelled into one slot and pushed, which amplifies what happens to the water.
Because learn of speeds vary depending on the part of the hurricane that hits a single location, a small change in the hurricane’s predicted path can cause a big transmute in the storm surge.
All these factors can make it difficult to predict how much thunder-shower surge will happen during a hurricane, Fogarty said.
That’s why it may end up being much gianter — or smaller — than predicted.
The water often returns very quick. After a negative surge from Irma, more than 1.5 metres of be inconsistent returned to one coast in less than an hour, he said.
«If you see water get strained out, it doesn’t mean to go out and explore,» Fogarty said. «It means something grotesque’s going on. You don’t want to be caught with the water coming back in.»