4 factors that play a role the rest of the hurricane season

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The Atlantic Basin has been pretty quiet so far this season, but that’s somewhat normal as we typically see a pick-up in tropical activity from August through September.


What do you want to know

  • La Niña conditions will persist in the Pacific Ocean
  • Saharan dust could play a role
  • The ‘MJO’ oscillation plays a big role
  • The placement of the Bermuda High and the speed of the trade winds play a role

So far this year, conditions have not been ideal for many tropical activities.

The Bermuda High east of Florida combined with lower pressure near the northern coast of South America, resulting in strong trade winds in the Caribbean. This creates hostile conditions for tropical waves and helps cool the water.

Although we had a few small, insignificant storms, conditions were generally calm.

Now that we’re entering the busiest part of the season, we’ll be keeping an eye on the various patterns to see how active this season will become.

(International Research Institution)

We know for sure that La Niña will continue in the Pacific Ocean. In the image above, you can see that La Niña will continue this fall and likely through winter.

When the Pacific Ocean swings at below average water temperatures, we call it La Niña. Looking at historical records, this generally translates to above average hurricane seasons in the Atlantic Basin.

(International Research Institution)

During these types of years, there is generally less wind shear over the Atlantic, which can allow tropical waves to thrive more easily. This likely means the Atlantic hurricane season will soon become more active.

However, there are other attributes that can counteract these La Niña conditions.

Although it is still early in the season, we noticed a lot of Saharan dust and dry air blowing in from Africa.

This will be something we will keep an eye on as at some point the dry air will retreat.

When this happens, it will leave the door open for more robust tropical waves to cross the Atlantic Ocean.

(NOAA)

Something you don’t hear about often, but which we watch behind the scenes, is the Madden-Julian Oscillation (MJO).

This is a global climate model from which we are still learning. We know that there are oscillating waves in the upper atmosphere that travel around the earth. As they pass overhead, they add lift to the atmosphere, which helps reduce surface pressures, i.e. when the weather is stormier.

Although their exact trajectory is difficult to predict, we have been able to track them more accurately over the past decade. This will generally give us an idea of ​​when the tropics will become more active.

So far in the season, the MJO hasn’t crossed the Atlantic Ocean, but that will likely change over the next month. As this pattern passes over our heads, it will almost certainly result in more tropical waves turning into hurricanes.

Once tropical storms form, the Bermuda High plays an important role in determining their exact path. The high pressure is constantly moving and therefore is something we monitor daily as it will give us an idea of ​​when the conditions will be present for a hurricane to track towards the United States.

As noted earlier, the Bermuda High can also play a role in the strong easterly trade winds that cross the Caribbean. That’s what happened this season. But in the past week, this pressure gradient has weakened, which will open the door for the organization of tropical waves as they approach the Caribbean.

We have seen some seasons when there are a lot of hurricanes in the Atlantic, but very few threaten land. And we’ve seen seasons where there are very few hurricanes, but they all impact the land.

Although large-scale weather patterns are ripe for this season to have above-average activity, the regional factors mentioned above will determine whether any of the tropical storms will impact land this year.

Like every year, we’ll be here to track every tropical wave in an unhyped way to give you the facts on what we’re seeing.


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