Surf Sci­ence: Hur­ri­canes in Costa Rica?

Howler Magazine - - Contents - By Ryan Wal­dron

On Septem­ber 18, 2017, six sep­a­rate trop­i­cal sys­tems were spin­ning some­where within the At­lantic, Caribbean, and Pa­cific basins. And from Oc­to­ber 4 to 6, Trop­i­cal Storm Nate left a wake of death, flood­ing and wide­spread de­struc­tion na­tion­wide. Although events like this are un­for­tu­nate for many, it makes sense from a cli­ma­to­log­i­cal stand­point as Septem­ber and Oc­to­ber are the peak of hur­ri­cane sea­son in the North­ern Hemi­sphere.

With all this trop­i­cal ac­tiv­ity, how is it pos­si­ble that Costa Rica is con­tin­u­ally spared from the di­rect im­pacts of ma­jor hur­ri­canes? Many of us re­mem­ber the (al­most) his­toric Hur­ri­cane Otto last Novem­ber, which brought heavy rains and winds across Costa Rica's north­ern re­gion. But if you re­mem­ber cor­rectly,

Otto of­fi­cially made land­fall — the lo­ca­tion where the eye of the storm first strikes land — along the Caribbean coast of Nicaragua, not Costa Rica. Do­ing your home­work on the sub­ject, you will find that a true hur­ri­cane, de­fined as a trop­i­cal cy­clone with winds over 74 mph, has never ac­tu­ally made di­rect land­fall on Costa Ri­can ter­ri­tory.

How is this pos­si­ble? The an­swer lies within the realm of the Co­ri­o­lis ef­fect. This phe­nom­e­non is a bit dif­fi­cult to ver­bal­ize, so I sug­gest do­ing fur­ther re­search your­self. It's im­por­tant to un­der­stand that the speed of earth's ro­ta­tion varies depend­ing on your lo­ca­tion. At the equa­tor, the earth is ro­tat­ing at 1,018 mph, while at 30 de­grees north lat­i­tude (roughly the Florida/Ge­or­gia bor­der), it's ro­tat­ing at 882 mph.

Imag­ine this: A plane takes off in Mi­ami head­ing true north to New York City. Be­cause the earth is ro­tat­ing faster at the equa­tor and slower to­wards the poles, the plane will ac­tu­ally be de­flected from its course if the Co­ri­o­lis ef­fect is not taken into ac­count be­fore take­off. In the North­ern Hemi­sphere, ob­jects are de­flected to the right while in the South­ern Hemi­sphere, they're de­flected to the left.

So how does this re­late to hur­ri­canes? Well, a hur­ri­cane is just a center of very deep low pres­sure that high pres­sure around it is try­ing to fill in the form of wind. As the wind trav­els above the earth's sur­face to­wards the core of the hur­ri­cane (the eye), the wind is al­ways be­ing slightly de­flected, giv­ing the storm its sig­na­ture spin.

Sit­ting com­fort­ably at about 8 de­grees north lat­i­tude, Costa Rica is too close to the equa­tor for the Co­ri­o­lis ef­fect to come into play. In fact, be­tween 10 de­grees south lat­i­tude and 10 de­grees north lat­i­tude, hur­ri­canes are prac­ti­cally un­heard of.

The earth is sim­ply too flat for the wind to be de­flected from its des­ti­na­tion and cre­ate the spin. And with our north­ern­most bor­der sit­ting at 9.55 de­grees north lat­i­tude, Costa Rica has been gra­ciously spared from ev­ery recorded land-fall­ing hur­ri­cane.

But you can never be cer­tain. As our cli­mate spi­rals out of con­trol and “black swan” weather events are be­com­ing more com­mon, the pos­si­bil­ity of Costa Rica be­ing di­rectly im­pacted by a hur­ri­cane is not out of the ques­tion. The best so­lu­tion is to al­ways stay in­formed and have a plan.

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