WEST PALM BEACH, Fla. (WPEC) — Heavy rain and strong winds are likely to batter parts of Central America this weekend into next week, but could it spawn the first tropical depression or storm of the 2022 Atlantic Hurricane Season?
You might have heard or seen some rumblings about a tropical disturbance brewing near Central America or the Gulf of Mexico into next week. While an area of low pressure is likely in this area, the chance for a developing tropical system looks very low – at least for now.
It's not a surprise to start thinking about a tropical disturbance in May. Since 2015, there has been at least one system form before the official June 1st start date each season.
One of the biggest influencers in pre-season storm activity is something known as the Central American Gyre (CAG). The CAG is a broad area of spin that sets up over Central America and provides enhanced moisture across the continent and the adjacent waters.
This CAG is what is likely to develop late this weekend throughout next week. Within the gyre itself, localized areas of spin can develop and under the right conditions, these local areas of spin could develop into a tropical system.
These CAGs most often form in early and late into hurricane season - typically May and June and once again in October and November. Occasionally you can see a gyre set up during the peak of hurricane season, but it tends to be more rare.
CAGs are so large that they can influence developmental patterns for tropical systems across both the Atlantic and Pacific basins.
Two years ago, Tropical Storm Cristobal formed in the southern Bay of Campeche before moving ashore in southern Mexico and then lifting back north across the Gulf of Mexico. It eventually made landfall in New Orleans, Louisiana, soaking much of the southeast along its path.
The CAG was not only the formation starter for Cristobal, but also the steering pattern influencer.
According to the National Hurricane Center, roughly 50% of all CAGs have a tropical cyclone associated with them at some point in its lifetime.
While that number seems high, it's not always a slam dunk.
The Global Forecast Systems (GFS) model - also known as the American Model - has been quite bullish on this CAG creating a tropical system late this weekend into next week. However, in recent runs - including as early as Wednesday morning - the model has significantly backed off this idea.
The GFS model has a great track record at detecting tropical storm formation across the Atlantic basin but also has some large biases that are typically noticed early in the season. One of these biases is the false alarm rate in the Caribbean Sea.
Other forecast models, such as the European Centre for Medium-Range Weather Forecasts (ECMWF) - also known as the European Model - suggest that the CAG will be forced west into the Central American continent. This will create flooding rains across several countries, but will also limit any development due to the system being generally located over the mountains of Central America.
This is the idea the American model has grasped to Wednesday morning, coming more in line with the European and a few other global models.
Even if a tropical depression were to form before it pushed inland across Central America, the system would face two other large obstacles in the short term.
The first is very fast wind shear. In May, winds typically are screaming across the Gulf of Mexico and Caribbean Seas as frontal boundaries, jet stream dips and enhanced trade winds all increase the wind speed in this area.
Wind shear is not friendly to tropical systems. Strong wind shear prevents thunderstorms from developing vertically, which can strengthen the system. Tropical systems need weak or no wind shear to further develop and strengthen.
Secondly, a large push of dry Saharan air is moving across the Atlantic and is likely to arrive late this weekend, spreading across the Caribbean and Gulf of Mexico.
Known as the Saharan Air Layer, or SAL, these bursts of very dry air help to stabilize the atmosphere over the Atlantic waters. They help to take moisture out from the atmosphere, a key ingredient that developing tropical systems need to thrive.
A stable and dry atmosphere will not lend much help to a developing tropical system, especially a weak and unorganized tropical depression.
The bottom line - a tropical depression or storm is not likely to develop across the Atlantic basin this weekend or next week. Heavy rain and a dangerous flood threat is likely to set up across Central America, however.
Some areas of Honduras, El Salvador, Nicaragua, Costa Rica and Panama may see upwards of 6+" of rain through this weekend, which could lead to mudslides in mountainous areas. Regardless of tropical development, this CAG will create some life-threatening weather.