...back to normal?

The 2009 Atlantic tropical storm season was the quietest since 1997.  It produced only nine named storms, of which just three became hurricanes.  An “average” season has eleven named storms, including six hurricanes.

The main reason for the lack of activity was an El Nino (warm Pacific current) that developed faster and stronger than expected.  Also, Sahara dust clouds (and ash clouds from the Montserrat volcano) were fairly constant through the summer.  The resulting wind shear blew out or turned away a lot of developing storms.  Only one – Erika – touched land in the Caribbean as more than a depression or remnant low.

In October, we suggested that a below-average season might not be a totally good thing.  Of course, we’re glad to do without the damage and danger, but tropical storms are part of our “normal” climate.  When they don’t come, we may have other problems.

The first of these is drought.  Many Caribbean countries – including Jamaica -- look to summer and autumn storms for a big part of their annual rainfall.  The Caribbean Institute for Meteorology and Hydrology measures rainfall and soil moisture in sixteen countries.  Since April, CIMH has been reporting “moderately dry” to “severely dry” conditions in eastern and northern Jamaica, and we’re now entering what is usually the least rainy part of the year.  The consequences have included widespread water shortages, especially in and around Kingston, and a sharply reduced coffee crop that could take two years to recover.

The second potential problem is reef damage.  The big waves and heavy rain that come with tropical storms keep inshore waters cool.  Without them, the risks of coral bleaching and disease increase.  (Bleaching happens when corals lose the algae that live in their cells, help to feed them, and give them colour.  “Thermal stress” – bright sun and warm water – is the main cause.)

However, a marine biologist who checks Montego Bay’s coral regularly thinks “We may have dodged that bullet -- for now.”  Divers and fishermen working around the Bay report only isolated bleaching.  NOAA’s mid-December Coral Reef Watch update has removed Jamaica’s coastal waters from its at-risk list.
What’s in store for 2010?  The Colorado State University hurricane team has taken its first look at the coming season, and predicts “average to above-average” activity.  The early forecast calls for 11 to 16 named storms, including 6-8 hurricanes, and a 53% probability that at least one major hurricane will track into the Caribbean.  The CSU team expects the El Nino condition to lose strength over the next few months, and points out that we are still in a long-term cycle of high storm activity.

A more “normal” storm season will help to clean and cool Jamaica’s inshore waters and restore groundwater levels.  This is no reason to feel safe.  Good luck may have bought some time for our reefs and reservoirs.  Only a big improvement in management can make sure they stay alive and productive.