The hurricane season starts June 1, 2016 and is likely to be more active than what we have seen in the past two previous years. There are several reasons why this year’s hurricane season is going to be more active. However, this does not necessarily mean that these tropical low pressure systems will all impact the United States.
NUETRAL ENSO TO LA NINA:
The changing states of ENSO from a warm phase (El Nino) to a cold phase (La Nina) can have a dramatic impact on the development of tropical low pressure systems in the Atlantic Ocean. This is mostly the case due to the impacts of wind shear on the Tropical Atlantic which can inhibit the development of tropical low pressure systems.
When an El Nino is in control, the Sub Tropical jet stream is much stronger and as a result the mid level wind shear is enhanced as strong 500 MB short waves tear apart most of the tropical disturbances moving through the Inter Tropical Convergence Zone.
This year, the Atlantic Tropical Season will start off with neutral influences however by the peak of Hurricane Season in mid August through late October, a La Nina should be in place.
The current mid and upper level winds right now already show an environment that is far more favorable for tropical low pressure system development. The relatively weak mid and upper level winds around large areas of mid and upper level high pressure in the Tropical Atlantic from the Gulf of Mexico to the African coast is strongly supportive of development this season.
The Tropical and western Atlantic are also provide clues for what to expect this hurricane season. Note, unlike last year, the sea surface temperature anomalies are above normal from the Caribbean Sea to the African coast and also over the western Atlantic. These locations are the most likely to have the most supportive environment for tropical low pressure system development.
With that being the case, I have noted the cooling of sea surface temperatures in the Gulf of Mexico which may be an inhibiting factor moving forward for the Gulf Coast.
As for influences on the East Coast of the United States, the very warm waters off the East coast actually tends to be an inhibitor for landfalling tropical low pressure systems. The reason why is due to the warm water attracting 500 MB troughs from the Polar jet stream towards the Mid Atlantic and New England coast, which as a result lead to tropical low pressure systems being forced back into the northern Atlantic.
The final impact to consider is the impacts of dust from the Sahara Desert. The best way to imagine the impacts of the Sahara Dust on tropical systems is observing the impact of diamond dry from baseball. When this dust hits a tropical low pressure system, the development of thunderstorms and thus latent heat release in the warm core low is disrupted.
This year, thus far the transport of dust off the African coast has been far weaker than in years past. However, if dust coming off the Sahara increases, then this factor will significant reduce the number of tropical storms and hurricanes this year.
Based on the data above here is the going forecast:
NORMAL: 10 Tropical Storms, 6 Hurricanes, 3 Major Hurricanes
FORECAST: 18 Tropical Storms, 10 Hurricanes, 5 Major Hurricanes
NOTE: Tropical Storms are total storms for the year.