Tag Archive | atlantic

New Developments on Tropical Cyclones and Climate Change

One of the goals of the Cyclone Center project is provide a more definitive answer on how tropical cyclones (TCs) have been responding to the dramatic changes that our climate is undergoing.  It is difficult for meteorologists to determine how strong tropical cyclones are getting because we rarely observe them directly, relying primarily on satellite data to give us a decent estimate of the wind speeds.  But as you can imagine, it is very hard to determine the maximum winds in a hurricane when you are in the hurricane itself, let alone flying more than 22,000 miles above it!  Our record of tropical cyclones is by no means nailed down.

http://www.epa.gov/climatechange/images/indicator_figures/sea-surface-temp-figure1-2012.gif

Ocean temperatures have been warming, which provides more energy for tropical cyclones (Image from the EPA)

So people have some differences of opinion on what has been going on in recent years.  Perhaps even more interesting is what will happen in the future.  There are theories that predict the characteristics of tropical cyclones in future years as the rate of ocean and atmospheric warming accelerate.  Most scientists believe cyclones will be more intense as global oceans warm.  There are reasonable disagreements on the number of tropical cyclones forming, since the formation of TCs are sensitive to other things like winds and moisture in the atmosphere.

In the Atlantic Ocean, which of course is of the most interest to the United States and Caribbean nations, the traditional view is that storms will be stronger but less frequent.  A recent study by Kerry Emanuel, a well-respected tropical meteorologist, suggests that we may not be so lucky.  Using the latest high-resolution computer models that simulate TC-like circulations, his results show a 40% increase globally in the strongest TCs (Category-3 or higherand an increase in numbers of TCs in several basins including the North Atlantic.  One has to always be cautious of computer model projections, and it remains to be seen if further evidence comes out to support Emanuel’s conclusions.  But we can accept without doubt that the threat of TCs will remain.

The work of citizen scientists like you on Cyclone Center is already producing results that will help rectify differences in the historical TC record.  As for the future, we’ll just have to wait a little bit on that.

- Chris Hennon is part of the Cyclone Center Science Team and Associate Professor of Atmospheric Sciences at the University of North Carolina at Asheville

2012 Atlantic Hurricane Season: Signed, Sealed, Delivered

The motto that isn't really a motto

The motto that isn’t really a motto

The United States Postal Service (USPS) has been delivering mail for over 200 years (and recently, losing a lot of money doing it).  Their motto, which apparently is not their official motto at all (just branded all over their NYC postal building) is well known: “Neither snow nor rain nor heat nor gloom of night stays these couriers from the swift completion of their appointed rounds”.  Notably missing from this statement  is “hurricane”, “superstorm”, or “storm hybrid” –  Hurricane Sandy showed that it is not possible to deliver mail when a good portion of your city is underwater.

Last Friday the Atlantic tropical season officially ended.  There isn’t a switch that gets turned off that prevents tropical cyclones from developing after November 30; in fact, we have seen storms form into January as recently as 2005.  Nevertheless it is beneficial to designate a tropical cyclone season; it gets people’s attention and does have some scientific merit.  The great majority of storms do form between June 1 and November 30, and storms that do form outside those times rarely affect the U.S.

Of course in other parts of the world the tropical cyclone seasons may be just beginning.  The conditions that allow for their formation in the northern hemisphere late summer/early autumn (warm ocean waters, favorable atmospheric conditions) are just now setting up as the season turns toward summer in the southern hemisphere.  In the tropical western Pacific,  where more  tropical cyclones form than any other basin, conditions are so favorable that storms can form year round.

For Americans, the 2012 tropical cyclone season will be remembered by one name – Sandy.  But it was quite an active season as well, with 19 storms becoming strong enough to earn a name.  This movie shows many of these storms:

Of those 19, only a handful were directly sampled with reconnaissance aircraft; for the rest, as well as storms in every other part of the world, their intensity were estimated primarily from the Dvorak technique.  Cyclone Center citizen scientists use a similar technique to classify historical tropical cyclones – one day Hurricane Sandy will be one of those that users will classify.

We launched the project back in September and it’s had more than 100,000 classifications so far. Cyclone Center is one of the most challenging projects ever built by the Zooniverse, but with each classification you’re contributing to our knowledge of tropical storms.

So far the Cyclone Center community has analyzed more than 500 storms as they raced across the globe. The weather data used on the site comes from 30 years of satellite images and so many memorable storms are being closely inspected by volunteers on the site each day: Katrina (2005), Andrew(1992) and Gilbert (1988) amongst them.

Interestingly, this is the 7th consecutive season that the U.S. was not impacted by a major (Category 3 or higher) hurricane – hard to believe after going through a storm like Sandy which technically may not have even been a hurricane as she came ashore.   As storms continue to become stronger in a warmer climate and societal impacts become more severe, it will be more difficult for mail carriers to make their appointed rounds…assuming mail delivery isn’t cut to 1 day a week by then anyway.

- Chris Hennon is part of the Cyclone Center Science Team and Associate Professor of Atmospheric Sciences at the University of North Carolina at Asheville – this blog is part of the 2012 Zooniverse Advent Calendar.

cyclonecenter.org

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