ORLANDO, Fla. – The two words you don’t want to hear during hurricane season is La and Nina.
On Thursday, the National Oceanic and Atmospheric Administration issued a La-Nina watch, meaning conditions are favorable for the development of La-Nina over the next six months.
A La-Nina watch is similar to the likes of a severe thunderstorm watch in the sense that conditions are favorable, but different since La-Nina isn’t a storm, rather an atmospheric pattern that can influence weather around the world.
What is La Nina?
La Nina is a seasonal ocean/atmospheric pattern that develops in the tropical Pacific. La-Nina is the cool phase of El-Nino Southern Oscillation or ENSO. During hurricane season, the phase ENSO is in can strongly impact tropical development far away in the Atlantic Basin.
When El-Nino, the warm phase, is present, tropical development is suppressed with increased wind shear and poor atmospheric conditions in the Atlantic Basin.
When La-Nina is present, waters along the Equatorial Pacific, off of the coast of Peru, are cooler than normal. This happens because the trade winds strengthen in that region, pushing warm water toward Australia, allowing cooler water deeper in the ocean to come to the surface. This is known as upwelling.
When this is occurring, wind shear, which hurricanes do not like, tends to be lower creating a much more favorable environment for storms to develop.
This helps to enhance tropical development. Rising air that is needed for thunderstorm development is also promoted in this situation.
Early-July La-Nina update
Higher-than-normal tropical activity forecasts were partially developed due to the lack of El-Nino, but it is becoming increasingly likely that a full-blown La-Nina could develop for the peak of hurricane season.
The Climate Prediction Center and International Research Institute for Climate and Society now gives a 54 percent chance that La-Nina will develop for the months of September, October and November, the peak of hurricane. That is an increase of 6 percent from their mid-June update.
Even though chances are growing that a La-Nina will be around for the peak of hurricane season, there is NO guarantee Florida will be impacted by a tropical system. Naturally, with the potential for more storms as forecast by NOAA, the chance of being impacted by a tropical system does go up.
The atmosphere over the next few weeks will become more conducive to supporting tropical systems that roll of Africa.
For a more in-depth look at the tropics through the middle of July click here.