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Science Alert: Experts Respond

Hurricane Sandy – Experts Respond

Posted in Science Alert: Experts Respond on October 30th, 2012.

Hurricane Sandy, currently hitting the East Coast of the United States, shares several similarities with Cyclone Giselle – which sunk the Wahine in Wellington in 1968 – according to experts.

Prof James Renwick, Associate Professor School of Geography, Environment and Earth Sciences, Victoria University Wellington, comments:

The Wahine lists Wellington Harbour

“Hurricane Sandy poses huge risks for the heavily populated northeast of the US.

“Sandy is a classic example of a tropical cyclone reinvigorating itself outside the tropics, drawing extra energy from a strong jet stream and a deep trough in the mid-latitude westerlies.

“Such storms can bring extremely damaging weather anywhere they occur. The ‘Wahine’ storm of April 1968 was very similar in many respects to Sandy, and brought hurricane-force winds to many parts of New Zealand.

“Beyond the wind and the rain or snow, one of the main dangers of hurricane Sandy is the storm surge.

“The low pressures in the centre of the storm ‘pull’ the sea surface up from its normal level, and the storm winds drive the water onto the coast. On top of that, we have the wind-driven waves reaching even further into coastal regions. The timing during a full moon adds extra risk, as tides are higher than normal this week along the east coast of the US.

“US authorities are predicting storm surges of three metres and more in places, enough to cause serious inundation in many low-lying areas (including lower Manhattan).”

New Zealander Prof Jim Salinger, Visiting Professor at Stanford University, California,  told the NZ SMC:

“Hurricane Sandy is the superstorm of the decade as the Wahine storm was the most destructive storm of the 20th century for New Zealand. The Wahine storm or Ex-tropical Cyclone Giselle formed in the Coral Sea on 5th April. Cyclone Giselle moved southeast.   On the 9th, it passed along the east coast of the North Island from North Cape, and after crossing Cook Strait the system travelled down the east coast of the South Island to Banks Peninsula, remaining close to the South Island for some days longer. It combined with an active cold, in the Tasman Sea as Giselle moved down New Zealand from 8 – 12 April. On the 12th, the cyclonic storm returned in a south-westerly direction and caused heavy flooding in Southland and West Otago. This affected every region in New Zealand, with high winds, heavy rain, flooding, landslips and high seas. The interislander ‘Wahine’ sunk in Wellington Harbour during the storm, with the loss of 51 lives.

“Cyclone Sandy started life in the Caribbean and has been cruising up the eastern seaboard of USA before it combines with an active cold front over the north east and jet stream aloft, which will make it ‘bomb’ as it turns inland just south of New York city to form a superstorm and stalls over the states of Pennsylvania and New York. Predicted impacts are massive: huge rainfalls with as much as 300 – 400 mm, high winds gusting up to 180 kph, massive storm surges  - up to 3 metres into New York and snowfalls of over half a metre in Pennsylvania and upstate New York.  It is a huge storm, being 1600 km wide – the distance between eastern Australia and New Zealand.

“The differences between the two are that Giselle affected a population of 3 million, Sandy is striking a populace of 60 million and impacts will be massive. Global warming puts more energy in to storms, loading them with extra rainfall making flooding more likely. Storm surge now rides on sea levels that have risen over the last century due to global warming, amplifying flooding losses where the surge strikes.  Climate change has stacked the deck of cards, making super storms of this kind more likely to occur.”     

Our colleagues at the UK SMC collected the following also collected the following expert commentary on Hurricane Sandy.  

Kamran Moazami, Head of Buildings Structures at engineering consultancy WSP and the structural engineer on the Freedom Tower in New York, said:

“New York is a city of skyscrapers but tall buildings are designed to withstand high wind loads – we design structures for a 50 year wind event, up to 98 miles per hour and on top of that structures are designed for a factor of safety.  The parts of the city that will suffer the most are the smaller structures and the infrastructure which makes up the nervous centre of the city.  As in any disaster it is the lack of water, power and transport and flooding that can have the most devastating impact and effect on the speed of recovery.”

Dr Jane Strachan, Willis Research Fellow at the University of Reading, said:   

“Although only a category 1 hurricane, Sandy is causing big problems for the U. S. northeastern states due to its huge size and slow movement up the U. S. East Coast. Powerful winds, torrential rains and storm surges threaten states from the Carolinas to New England, and yesterday the National Hurricane Center warned of a storm surge affecting New Jersey, Long Island and New York Harbour of between 2 and 4 metres.

“After killing 60 people in the Caribbean last week, Sandy moved north and northeastward parallel to the southeast coast of the U. S., but today is expected to be drawn back northwestward toward the coast and is forecast to make landfall in southern New Jersey tonight. However, Sandy won’t have to come onshore for it to cause serious problems for the U. S. East coast.  Storm surge and the associated flooding are the biggest worry, due to the strong winds and very low pressure, coinciding with high tides associated with a full moon.  Additionally, heavy rains of up to 50mm per hour associated with this large and slow moving are making flooding a major concern.

“As Hurricane Sandy merged with a cold front, it has grown to over 3200 km in diameter and is now the largest hurricane in Atlantic storm history. Additionally, the storm is changing from tropical to extratropical in its structure, so that rather than the winds being more focused around the eye of the storm, the tropical-storm-force winds, reaching over 135 km/h, have spread out and are affecting a much larger area.

“Something that threatens hurricane monitoring is future satellite coverage of tropical storms. Vital information from polar satellites is fed into the models that help forecasters predict the path of storms like Sandy, providing warning information for the Caribbean and U.S. However, as a result of years of mismanagement, lack of funding and delays in launching replacements, it looks very likely that there will be a gap in polar satellite coverage, which would lead to reduced forecast quality. This was the worrying headline news in Friday’s New York Times, with existing satellites are nearing the end of their lives, while the launch of the next replacement (JPSS-1) has slipped to 2017, leading to a gap in coverage of at least a year.”

Professor Mark Saunders, Department of Space and Climate Physics at University College London, said:

“The situation with Hurricane Sandy will not become certain until after landfall late today (US east coast time).

“However, the two most unusual features of hurricane Sandy which may well make it unique as a storm are its track direction and curvature, and its relative strength.

“From a location well offshore at a latitude of 35°-40°N the storm turns to the northwestward to strike the US mid-Atlantic coast. There is no precedent in hurricane records extending back to 1851 of a storm at this latitude taking this path. All historical hurricanes located well offshore at this latitude have followed the jet stream and tracked in a direction between north and east.

“Sandy’s central pressure is currently forecast to be 945-950mb at landfall late on Monday. A pressure this low would exceed the previous record low pressure of 955mb for a hurricane landfall in this region at this time of year. It would also be close to the record low pressure of 946mb for any hurricane landfall north of Cape Hatteras; this record  holder being the ‘New England’ hurricane which  occurred in September 1938.”

 

See also: UK Met Office blog on the hurricane.

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