Hurricane Sandy terrible but amazing
The US is experiencing a rare meteorological event as a cold front from Canada pushes Hurricane Sandy inland, reports Paul McGeough from Washington DC.PT2M40S http://www.canberratimes.com.au/action/externalEmbeddedPlayer?id=d-28gfl 620 349 October 30, 2012
THIS one is bigger than Sebastian Junger's The Perfect Storm, more complex than the notion that the flapping of a butterfly's wings in the Amazon might cause a storm in New York's Central Park.
This is not just about Hurricane Sandy, which you have been hearing about as background noise in the news for the past week – how it did this that or the other as it wreaked havoc in the Caribbean before heading north and west towards the densely populated north-east corner of the US. Cities such as New York, Boston, Baltimore, Philadelphia and Washington – get my drift.
One of several intimidating meteorological characters in the mix, Sandy has been churning up the Atlantic since last week and just now, as I write, has shrouded my home in the drab darkness of a greater Washington afternoon without electricity. Now scratching this by torchlight as Sandy steps up speed – on Sunday afternoon she was making a sedate 20 km/h; 24 hours later she's stepping out at 45 km/h.
Making waves ... Hurricane Sandy. Photo: Reuters
Those other characters?
An Arctic jetstream pushing down from Canada and Greenland and a low-pressure winter system moving in from the west are combining to block what ordinarily would be Sandy's course – which would be to head towards the mid-Atlantic US coast and then to head back out to sea, following the warmth of the Gulf Stream. Instead, it's going to New York, crossing the coast near where New Jersey meets Delaware, and then on to Maine in the north and north-west towards the Great Lakes.
And because of all this hot and cold and surging, the brilliant autumn colours that we'd expect in this corner of the US for weeks to come are being stripped from the trees this very afternoon and communities from West Virginia and even North Carolina will be getting feet of snow or inches of rain – instead of the balmy autumn weather they expect.
Hurricane Sandy is breaking records. Photo: Reuters
And because of that blocking effect, Sandy will be dawdling through the north-east, it's effects lingering for as much as 36 hours in most of the areas it hits.
The sustained wind speeds, not to be confused with gusts, are tipped to reach 120 km/h. The gusts will be 130 km/h and higher.
The predicted rainfalls are not to be sneezed at: 10 to 20 centimetres in much of the affected area – and in some places even 30 centimetres. Snow in the high country of West Virginia could be 60 centimetres or more.
A full moon which creates high tides which make storm surges at sea bigger and bolder than might be imagined - think two to four metres high at lower Manhattan's Battery Park – a foot or two higher than the record surges of 1990. That means coastal flooding and inundation for man-made systems that can't be drained adequately – like New York's sprawling underground rail system, which had a close call with flooding when Tropical Storm Irene hit last year.
Sandy has an unusual pedigree. Most hurricanes draw their power from warm seas. But while Sandy's genesis were a tropical wave in the west of the Caribbean on October 22, it has evolved into what the experts call an "extratropical" storm, one that is gassed up by atmospheric contrasts.
Even before landfall, Sandy was smashing records – it had overtaken Lili (1996) as the biggest Atlantic storm in 24 years of record-keeping. Its tropical-storm force winds reached to more than 800 kilometres from the centre; its hurricane winds were stretching 280 kilometres from the centre. By hurricane standards, those are exceptional distances.
The atmospheric pressure at its centre was getting down to a record set in the late 1930s. At 951 millibars and tipped to go as low as 935 millibars, Sandy's pressure was lower than any previously recorded in New Jersey and significantly lower than the 968-millibar record set by Hurricane Isaac when it clubbed New Orleans last year.
You've read to here to pick up the reference to the Amazon butterfly? Well, the parallel is this – the hurricane that is coming up from the Caribbean to do a dump on New York and the six or seven surrounding states, may be as bad as it is because of something that is happening up in the Arctic.
That ridge of high pressure pushing down from Canada and Greenland, a blocking high as it is called in the trade, has an intensity that intrigues meteorologists because, they suspect, is is caused by the reduced sea ice in the Arctic – all a part of climate change.
As reported on Climate Central: "The 2012 sea ice melt season, which ended just a month ago, was extreme, with sea ice extent, volume and other measures all hitting record lows."
And why does this make a difference?
"The loss of sea ice opens large expanses of open water, which then absorbs more of the incoming solar radiation and adds heat and moisture to the atmosphere, thereby helping to alter weather patterns."