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Wednesday 8 November 2017

Worst week of wildfires on record devastates California

At the same time as the devastating wildfires in Portugal and Spain described on 25 October [AWN], California experienced the worst wildfires in the history of the state both for loss of life and property. In the week from 8 October, hundreds of wildfires coalesced into 21 major conflagrations that brought firestorms on a front over 150km wide to the Napa/Sonoma area famous for its wines north of San Francisco. The fires were only slowly brought under control, with five still active at the end of October.

The Calfire Statewide Fire Summary* reported that the fires "burned over 245,000 acres, 11,000 firefighters battled the destructive fires that at one time forced 100,000 to evacuate, destroyed an estimated 8,900 structures (as damage assessment continues, this is the latest count), and sadly, took the lives of 43 people."

Common factors were at work in the Iberian and Californian fires: hot, dry, strong winds following a long period without rainfall during which forest and grassland dried to provide ready fuel for wildfire. Both areas experience Mediterranean climates, with long, dry hot summers so that October, early autumn, has the greatest incidence of major fires based on past records. But there were significant differences between the two catastrophes.

Portugal and NW Spain were unlucky to be affected by the strong outer winds of Hurricane Ophelia, the easternmost Atlantic Hurricane in the records since 1851 [NOAA], just at the time it was transitioning into a major Hurricane. This very rare meteorological event brought hot, dry air from the African Sahara along with gale force winds, the worst possible combination for forest fires. Large areas of central and northern Portugal and NW Spain are forest country with relatively sparse population, and with around 600 fires burning at the height of the event, firefighting systems were overwhelmed. In addition, questions have been raised about both countries' preparedness in forest management practices, evacuation procedures, fire defense infrastructure and fire education.

Central California, on the other hand, regularly experiences hot, dry Diablo and Santa Ana winds in October, which can reach well above gale force as they fan out from the interior over the coastal mountains and through canyons onto the plains. Raging wildfires have been part of the seasonal routine for at least the 5,000 years of human habitation. This year, a very wet winter provided ample fuel to be dried by a record hot Californian summer. The most damaging fires were concentrated into large blazes and affected outer urban areas with relatively high population densities, accounting for the large loss of homes and other structures [New York Times]. That there not more deaths is partly due to preparedness.

The population explosion into an area that is naturally highly wildfire-prone is the major problem, as it has become in Australia. Calfire's preliminary estimate of 5,643 structures lost in the main Tubbs fire in this event is twice that of the previous highest loss of 2,900 in the Tunnel fire in Oakland Hills of October 1991 with another three blazes in October 2017 having the dubious distinction of a listing in their Top 20 Most Destructive California Wildfires. In a good article headed California’s wildfires aren’t “natural” — humans made them worse at every step, Vox shows one study that projects that by 2050, 645,000 houses will exist in very high wildfire severity zones, the state's highest level. Much of the article will sound familiar to Australian capital city dwellers.

Additional useful references are this Wikipedia entry that is being progressively updated with new information, and Weather Underground blogs by Bob Henson and Sean Breslin, both written at the height of the fires examining the meteorology behind them and the experiences of those who lived through them.

Australian weather briefs

• A severe thunderstorm struck Bundaberg QLD late on Tuesday afternoon, 7 November. Described in an ABC News story as "the worst non-cyclonic storm to hit the region in a decade", the supercell thunderstorm hit the Airport just before 17.00 with a gust of 98km/h, the strongest there in over 20 years. Wild wind tore roofs off homes, lifted a shed off its footings and hurled it across a road and downed about 200 powerlines and many trees, including a century-old fig tree. The Airport recorded 22.8mm in the 10 minutes to 17.00 and photographs around Bundaberg show the ground covered in hail. Ergon Energy said that 26,000 premises in Bundaberg lost power, with at least 10,000 spending the night without electricity. The ABC News story yesterday has two videos that give a good feel for what was a spectacular event.
• Elsewhere in QLD on Tuesday afternoon, strong winds and hail lashed the Sunshine and Gold Coasts and Brisbane area. Hail to 4cm was reported from Kandanga, S of Gympie, and Beaudesert inland from the Gold Coast, while Double Island Point, 50km ENE of Gympie, reported wind gusts to 107km/h. Flights at Brisbane Airport were delayed by up to an hour during the storm there.
• In NSW, damaging storms hit the lower Hunter Valley and Central Coast around mid-afternoon on Monday 6 November. The worst damage occurred in Kurri Kurri, 10km SW of Maitland, where SES told ABC News that the strong wind caused a community centre roof to collapse, unroofed some houses and brought trees down on others. Ausgrid said 7,000 premises lost power, while Kurri Kurri Public School was closed by storm damage. On the Central Coast at Toukley, the wind was strong enough to lift a catamaran onto the roof of a house, and local blackouts occurred around Wyong.