…why we need “bad” weather

When the Colorado State University hurricane team issued a late-season update a few weeks ago, they trimmed their forecast to10 named storms, of which four will be hurricanes. That means two more hurricanes in the next five weeks.

The 2009 season has certainly been quiet in the Caribbean. The forecast El Niño (warm Pacific current) developed faster and stronger than expected, and Sahara dust clouds were fairly constant all summer. The resulting wind shear blew out or turned away most of the eight storms so far. Only one – Erika – touched land in the Caribbean as anything more than a depression or remnant low. Is this good news? Of course we’re glad to do without lost roofs, washed-out roads and tense nights in emergency shelters, but these storms are part of our “normal” climate. When they don’t come, we may have other problems. First and most important of these is drought. Many parts of the Caribbean look to summer and autumn storms for most of their annual rainfall. Now they are reporting parched fields and gardens, empty cisterns and reservoirs, and concern about the months ahead – usually the year’s driest. The Caribbean Institute for Meteorology and Hydrology tracks rainfall and soil moisture in sixteen Caribbean countries. Looking at the April-to-September period, CIMH reported “moderately dry” or “severely dry” soil conditions in seven of these countries, including the eastern part of Jamaica. By September, in spite of a damp spring, all northern Jamaica was “severely dry”.

To the end of September, Montego Bay had seen only 27.6 inches of rain. Even if the rest of 2009 equals last year, the total – just over 39 inches – would be well short of the long-term average. It’s far below 2005 and 2007 – “hurricane years” with more than 60 inches of rain.

The second hazard is reef damage. Tropical storms can have some benefits for the reefs. Big waves and strong currents bring cool, food-rich water up from the deep ocean, and sweep exposed areas clean of silt and algae. They also add fresh water to keep the sea’s saltiness within the limits marine life can stand.

The U.S. National Oceanic and Atmospheric Administration (NOAA) reported that sea surface temperatures around the world in June were the highest it has ever recorded. The prospect of less-than-normal storm cooling led to a warning from NOAA’s Coral Reef Watch in July about “significant coral bleaching and infectious coral disease outbreaks in the Caribbean”. (Coral 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. )

Divers and fishermen working in and near Montego Bay report little or no sign of bleaching so far. A marine biologist who inspects the Bay’s reefs regularly feels “We may have dodged that bullet -- for now.” NOAA’s mid-October update still shows “potential widespread bleaching” all around Jamaica’s southern and western coasts.

If it has no other problems, healthy coral can recover from short periods of bleaching. However, Montego Bay’s coral is already stressed by pollution, silt, and an unbalanced food chain with too much algae and too few fish. Good luck may have bought our reefs some time, but only good management can make sure they survive.