2017 Atlantic Hurricane Season: Expect It to Be Busier Than Usual
- Colorado State University expects 14 named storms, six hurricanes and two major hurricanes this season.
- NOAA expects 11 to 17 named storms this season, more than the 30-year average for the Atlantic Basin.
- The Weather Company predicts 14 named storms, seven hurricanes and three major hurricanes this season.
- Warmer North Atlantic sea surface temperatures and the reduced likelihood of El Niño's development are among the factors taken into account.
The 2017 Atlantic hurricane season is forecast to be more active than historical averages with regard to the number of named storms, according to the latest forecasts released by Colorado State University, the National Oceanic Atmospheric Administration and The Weather Company, an IBM Business.
The Colorado State University (CSU) Tropical Meteorology Project outlook headed by Dr. Phil Klotzbach updated its forecast Thursday, calling for an above-average number of named storms with 14 expected. CSU forecasts an average number of hurricanes this year, with six expected in the Atlantic Basin. A below-average number of major hurricanes – two – is also anticipated.
The 30-year historical average (1981-2010) for the Atlantic Basin is 12 named storms, six hurricanes and three major hurricanes. A major hurricane is of Category 3 strength or higher on the Saffir-Simpson Hurricane Wind Scale.
NOAA issued its forecast at the end of May and called for:
Eleven to 17 named storms – including April's Tropical Storm Arlene.
Five to nine of which would become hurricanes.
Two to four of which would become major hurricanes.
An important note is that Tropical Storm Arlene, which formed in April, is included in the seasonal forecast numbers in the outlooks.
According to NOAA, "The outlook reflects our expectation of a weak or non-existent El Niño, near- or above-average sea-surface temperatures across the tropical Atlantic Ocean and Caribbean Sea and average or weaker-than-average vertical wind shear in that same region."
Strong El Niños typically lead to increased wind shear in parts of the Atlantic Basin, suppressing the development or intensification of tropical cyclones in the Atlantic, so the prediction for weak conditions increased the chance for more activity this season.
"The climate models are showing considerable uncertainty, which is reflected in the comparable probabilities for an above-normal and near-normal season," NOAA added.
The Weather Company updated its seasonal forecast earlier in May and expects a total of 14 named storms – seven hurricanes and three major hurricanes – this season. This is an increase from its forecast compared to April due to a couple of factors.
One of the reasons is that warmer sea-surface temperatures have been observed in the North Atlantic, which have correlated with more active seasons in the past. In addition, there are indications that further warming is likely.
Another factor the outlook cited is that there is a reduced potential for the development and strength of El Niño later this summer.
Given the current trends, there is the potential for another increase with the next update in June. "The historically strong North Atlantic blocking event in early May also suggests the possibility of continued increases in North Atlantic sea-surface temperature anomalies, so it would be no surprise if we increased our forecast numbers again," said Dr. Todd Crawford, chief meteorologist with The Weather Company.
However, Dr. Phil Klotzbach noted, "While the tropical Atlantic is warmer than normal, the far North Atlantic remains colder than normal, potentially indicative of a negative phase of the Atlantic Multi-Decadal Oscillation (AMO). Negative phases of the AMO tend to be associated with overall less conducive conditions for Atlantic hurricane activity due to higher tropical Atlantic surface pressures, drier middle levels of the atmosphere and increased levels of sinking motion."
The official Atlantic hurricane season begins June 1 and runs through Nov. 30. Occasionally, storms can form outside those months as happened this year with Tropical Storm Arlene. This also occurred last season with January's Hurricane Alex and late May's Tropical Storm Bonnie.
Source: The Weather Channel