Latest Update - 12 August 2018 at 11.00 p.m.
Confidence that 2018 will experience a below-normal hurricane season increased substantially this week as global forces align to temper tropical activity.
An updated forecast released on Thursday by the US government Climate Prediction Center is now announcing a 60% chance of a less active storm season, a hefty change from a May forecast that predicted only a 25% probability of below-normal activity. Gerry Bell, the centre’s lead seasonal hurricane forecaster, said that the growing likelihood that a storm-thwarting El Niño will form, combined with Atlantic water temperatures that are the coldest since the 1990s, were key factors in making the new prediction.
The forecast comes as Florida enters the peak of hurricane season, from mid-August to October, when 95% of hurricanes form. Four named storms – Alberto, Beryl, Chris and Debby – have already spun up this season. Beryl and Chris both mustered hurricane strength, with Chris intensifying to a Category 2 storm with peak wind speeds of 105 mph (170 kmph).
As of Thursday afternoon, Tropical Storm Debby was still churning harmlessly in the northern Atlantic. “The season is not dead,” said Stanley Goldenberg, a meteorologist with the Hurricane Research Division of the National Oceanic and Atmospheric Administration. “Storms can pop up quickly and we do expect more storms.” The updated forecast predicts 9 to 13 named storms, including the 4 that have already formed. Also, 4 to 7 hurricanes are expected, with up to 2 major hurricanes of Category 3 or higher.
An average hurricane season has 12 named storms, 6 hurricanes and 3 major hurricanes. Bell said that, when the May forecast was released, the chances for El Niño were only 45%.
An update this week put the odds of an El Niño forming in the autumn at 65% and of a winter El Niño that could last into 2019 at up to 70%. Bell compared the current season to 2015, which had 11 named storms and 4 hurricanes.
But one of those hurricanes was Joaquin, a powerful Category 4 storm that killed 33 people when the cargo ship El Faro sunk near Crooked Island in the Bahamas. “Please remember the hurricane seasonal outlooks are a general guide and do not predict land-falling storms,” Bell said. “Whether or not a storm strikes land is determined by the weather patterns in place when the storm approaches and those are generally not predictable until five to seven days in advance.”
The planet was put on an El Niño watch in June. It’s not officially declared present until ocean temperatures in the equatorial Pacific are more than 1 degree above normal and are expected to maintain that temperature for 6 months. After that, it can take 30 to 60 days for the atmosphere to respond.
“If El Niño forms in October, it could shut the latter half of the season down,” Bell said. The onset of El Niño occurs in tandem with the relaxation of the trade winds. With the trade winds reduced, warm water that has piled up in the western Pacific Ocean and around Indonesia rushes back towards the east. That movement of warm water shifts rainfall patterns and the formation of deep tropical thunderstorms. Exploding storms whose cloud tops can touch the jet stream disrupt upper air patterns, so winds come more out of the west. The west winds create shear in the Atlantic, which can be deadly to budding hurricanes. When the Atlantic has lower tropical activity, the Pacific typically sees an increase. The Pacific’s storm tally, as of Thursday, was 11 named storms, including Hurricane Hector – a powerful 120 mph (195 kmph), Category 3 storm that is skirting along just south of the Hawaiian islands.
“The main message should be that, no matter what this or any other prediction says, that people must treat this like the peak of hurricane season and be prepared,” Goldenberg said. “Remember, 1992 was overall a very slow year.” Category 5 Hurricane Andrew – the first named storm of the 1992 season – devastated areas of South Florida when it ploughed ashore in August. 24.
Colorado State University has also reduced its early-season hurricane forecast, based largely on the cooler sea surface temperatures in the tropical Atlantic.
Lead CSU forecaster Phil Klotzbach said unusually strong high pressure in the Atlantic has driven stronger trade winds, which increased evaporation and the upwelling of cooler ocean temperatures from below the surface. Warm water is a main source of nourishment for hurricanes. Cooler water temperatures can discourage their formation. “The hurricane season is far from being over,” Bell said. “We urge continued preparedness and vigilance.”
22/11, 08/12, 24/12 – St. Thomas to Barbados
14/12 – Martinique to St. Thomas
11/11 – St. Kitts to San Juan
18/10 – Key West to Falmouth
14/11 – Labadee to Perfect Day at CocoCay
10/12 – St. Maarten to St. Thomas
12/10 – St. Lucia to Antigua
9/12 – San Juan to St. Kitts
11/11 – St. Kitts, St. Maarten & San Juan to Grand Cayman, Cozumel & Ocho Rios
14/12 – Perfect Day at CocoCay to Nassau
29/12 – Key West to Cozumel
24/11 – St. Thomas, St. Croix, Dominica & St. Maarten to St. Kitts, Barbados, St. Lucia & St. Thomas
22/12 – Ponce to St. Thomas
5/1, 26/1, 30/3 – Dominica to Martinique