Stormy Florence’s unique path from Africa to US linked to global warm­ing

In North Carolina, storm surge broke a 64-year-old high tide mark record set by a 1954 hur­ri­cane

The East African - - OUT­LOOK - By BRIAN K. SULLIVAN Bloomberg Bloomberg’s Jim Ef­s­tathiou Jr. con­trib­uted.

Born off the coast of Africa, Hur­ri­cane Florence fol­lowed an extraordinarily straight path to the US East Coast that beat his­toric odds, stun­ning fore­cast­ers and spurring new concerns over the dam­ag­ing effects of global warm­ing.

Al­most all storms that orig­i­nate where Florence did turn north­ward in the mid-at­lantic. But a stub­born, un­mov­ing high-pres­sure ridge that is in­creas­ingly be­com­ing the sig­na­ture for a warm­ing planet held it on a di­rect path to the Caroli­nas, sci­en­tists said. It ar­rived last Thurs­day, when the outer bands of the storm first hit North Carolina, car­ry­ing sting­ing winds and lash­ing rains that are fore­cast to last for days.

“It is ex­tremely rare to get a storm cross­ing at the lo­ca­tion it did,” said Jeff Masters, co-founder of the Weather Un­der­ground in Ann Ar­bor, Michi­gan. “It is a 1 or 2 per cent kind of thing.”

As the amount of Arc­tic ice and snow has fallen, seas in the north­ern hemi­sphere have warmed, and the air above has re­acted, said Jen­nifer Fran­cis, a cli­mate re­searcher at Rut­gers Univer­sity in New Jersey.

The prob­a­ble re­sult, ac­cord­ing to Fran­cis: High pres­sure ridges and low pres­sure troughs that tend to hold in place through­out the sum­mer.

This sum­mer, the ridge was “so per­sis­tent,” that it did not al­low Florence to veer from its west­ward march, Ms Fran­cis said by tele­phone.

“A sim­i­lar thing hap­pened to Sandy. It ran into a block­ing high and it shot west in­stead,” she said of the hur­ri­cane that en­gulfed the East Coast in 2012.

And Hur­ri­cane Florence and Sandy are not the only cli­mate events af­fected by this phe­nom­e­non, she said. For the past few years, sum­mer weather pat­terns across the North­ern Hemi­sphere have been ce­mented in place for the sea­son, lead­ing to record heat waves in places such as wild­fire-rav­aged Scan­di­navia, and to the flood­ing rains that plagued the mid-at­lantic and Wash­ing­ton sub­urbs.

While that may ex­plain how the hur­ri­cane got to the US, it does not say why it got be such a mon­ster. Kevin Reed, a pro­fes­sor of marine and at­mo­spheric science at Stony Brook Univer­sity in New York, be­lieves he may have an an­swer.

Us­ing tools de­signed to search for cli­mate-change sig­nals in past storms, Reed’s ed­u­cated guess is that Florence was some 130 km wider than it would be in a world with­out mod­ern lev­els of green­house gases.

Also, it could drop 50 per cent more rain in the places where the pre­cip­i­ta­tion is at its worst, he said. Fore­cast­ers said the storm could drench the re­gion with as much as 40 inches of rain.

Tens of thou­sands of struc­tures were flooded by the storm surge alone, North Carolina Gov­er­nor Roy Cooper said at a press con­fer­ence last Thurs­day.

“Our great­est con­cern about this storm re­mains the same — storm surge and mas­sive flood­ing,” Mr Cooper said.

The prob­a­ble cul­prit, ac­cord­ing to Reed and his col­league Michael Wehner, a staff sci­en­tist at the Lawrence Berke­ley Na­tional Lab­o­ra­tory in Cal­i­for­nia: Ex­tra wa­ter in a warmer at­mos­phere that turns into rain when a storm rolls through, in this case a very big storm.

“Af­ter the storm we will hun­ker down, and we will be able to see how right we were and should be able to say more in a week or two,” Reed said.

“We live in a world where cli­mate change is hap­pen­ing and all these storms are be­ing im­pacted.”

In the mean­time, sci­en­tists are closely mon­i­tor­ing Florence’s next steps. Some fear that once on shore, it could be blocked by yet an­other high pres­sure ridge, this one sit­ting off the na­tion’s mid­sec­tion, caus­ing it to wring it­self out like a wet sponge across North Carolina and South Carolina as it slowly creeps west.

As the world warms there may not be nec­es­sar­ily larger num­ber of hurricanes, ty­phoons and cy­clones, but the strong­est ones will be even more in­tense, said Colin Zarzy­cki, a pro­ject sci­en­tist at the Na­tional Cen­tre for At­mo­spheric Re­search in Boul­der, who works with Reed.

“We are load­ing the dice in favour of more of these high im­pact­ful weather events go­ing for­ward,” Mr Zarycki said. In the fu­ture “The type of events we used to see once in 50 years we may see once in 10 years.”

In Beau­fort, North Carolina, about 153 km north­east of where Florence hit land­fall, the storm surge broke a 64-year-old record, hit­ting 3.74 feet above the high tide mark, Masters said. Since Hur­ri­cane Hazel hit in 1954, ocean lev­els have risen 8 inches in the area be­cause of global warm­ing, he added.

“We would not have bro­ken the record if it had not been for that ex­tra 8 inches,” he said.

Florence was some 130km wider than it would be in a world with­out mod­ern lev­els of green­house gases.” Kevin Reed, a pro­fes­sor of marine science at Stony Brook Univer­sity in New York

Pic­ture: AFP

Iris Dar­den gets a lit­tle help to dry land af­ter wa­ter seeped into her home in North Carolina af­ter the pass­ing of Hur­ri­cane Florence.

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