August 23, 2022
… bumping up the forecasts
The hurricane forecasting season reached its peak a couple of weeks ago, just as the storm season was about to get under way. NOAA delivered its 2017 outlook at the end of a week of public education, much of which was spent showing off a battery of new tools for observation and data processing. The agency gives a 70% probability to a season with 11–17 named storms of which 5–9 become hurricanes, with 2-4 major hurricanes.
This is a fairly aggressive prediction. Even the bottom of the ranges comes very close to the long-term average. NOAA’s forecast rests on two main points. First, the agency expects only a weak El Niño (warm current), or none at all, in the eastern Pacific this year. No El Niño means less wind shear to blow apart any tropical storm that makes its way into the Caribbean Basin. Second, NOAA expects sea surface temperatures in the tropical Atlantic and the Caribbean to continue getting warmer, providing more fuel for developing storms.
In early April the respected forecasting team at Colorado State University predicted a slightly below-average season in 2017, expecting a moderate El Niño to be in place by September. Several private forecasters produced similar outlooks, all calling for close to average seasons. However, the signs of a developing El Niño have faded in recent months.
As for sea surface temperature, NOAA’s own satellite observations show most of the Caribbean and the western tropical Atlantic still within about one degree of its long-term average. In fact, the area around Jamaica is slightly cooler than normal. What has warmed up since early this year is the eastern side of the tropical Atlantic.
For most of last year, a stream of unusually cold water has been making its way south past the African coast, invading the main hurricane development region. In the 2016 season the west coast of Africa was not very productive. The “cold blob” allowed few storms to get started, and most of them were quickly swallowed by a heavy layer of hot, dry Saharan dust that had drifted further south than usual.
Between March and May this year, the sea off western Africa has swung from being at least one degree cooler than average to a couple of degrees warmer. The Saharan Air Layer is heavy but conditions are more favourable for early season storms to develop.
There is still a lot of uncertainty about whether the El Niño will develop and how much the tropical Atlantic will warm up over the next few months. However, several teams (including CSU) whose first forecasts appeared early in the year have revised them to slightly above average levels in the last few weeks.
By now, hurricane preparations should be well under way. Damage from this year’s heavy spring rains has produced more effort than usual to encourage the public to “plan, pray and be prepared”. .President of the Incorporated Masterbuilders Association, Humphrey Taylor urged householders to check roofs and window frames before bad weather comes, trim trees, clear drains and waterways and clean up their yards. RADA’s livestock specialist Maxine Brown urged farmers to make cooperative plans to move stock to higher ground when a storm approaches. She also advised making sure that farm buildings have proper drainage, cleaning up debris in farm yards, and storing livestock records, medication and first aid supplies securely.
Even the Caribbean Institute for Meteorology and Hydrology, the region’s drought monitor, has weighed in. The Institute noted that rain from a “normal” hurricane season would go a long way to relieve the long dry spell that has afflicted much of the region. However, a CIMH spokesman pointed out that intense rainy periods carry a flood risk both for countries like Jamaica, where the ground is already soaked, and for very dry areas where water would be slow to soak into hard-baked earth.
Whether the forecasts call for two storms or twenty, the only one that matters is the storm that’s in your yard. It’s never wrong to be ready.