2020 Revised Atlantic Hurricane Forecast

While we are less than two weeks into the Atlantic hurricane season, we have already seen three named storms. 2020 has broken the record for the earliest third named storm with Cristobal. An active early season has little correlation to the rest of the season, but a very active season is expected nevertheless. In my revised forecast for the 2020 hurricane season, I have bumped up my numbers slightly, but overall, it remains similar to my original forecast. I've given my forecast logic below, explaining each factor that led me to my forecast.

Let's start with one of the most influential factors in a hurricane season, the El Niño Southern Oscillation (ENSO). Two months ago, we were in an El Niño but were expecting the ENSO to drop to a cool neutral state by peak hurricane season. We have cooled faster than anticipated, however, and a La Niña looks very possible by peak season. So how does a La Niña affect the hurricane season?

The Walker Circulation: ENSO's atmospheric buddy | NOAA Climate.gov

When the ocean and atmosphere are both in a La Niña state (as they look to be this year), large scale subsidence occurs over the Pacific Ocean. This creates a branch of rising air over the Atlantic, which allows thunderstorms to easily form, creating a favorable environment for tropical cyclones. La Niña also reduces wind shear over the Atlantic, making the basin even more favorable.

Now, let's talk about the current sea surface temperature anomaly (SSTA) configuration in the Atlantic. As you can clearly see, we have a horseshoe of +SSTA's surrounding a pool of -SSTA's. This is a classic configuration that we see with above-average hurricane seasons. +SSTA's are located in the Main Development Region (MDR), which provides fuel for tropical waves.

The SSTA configuration isn't perfect, however, because the warmest water is not located directly in the MDR. Warm water enhances the rising motion in the air, so if this were to persist into peak season, the strongest rising would be located away from the MDR. This could cause sinking motion over the MDR, which would hurt tropicals waves. There are hints that the warmest water will migrate to the MDR, however, so we'll just have to wait and see.

This plot is not dissimilar to the PNA

Another important factor for the hurricane season is the West African Monsoon (WAM). This is what creates our tropical waves, so the strength of the monsoon is very important. As we have seen frequently this century, the WAM is very active, with above-average moisture content over the entire Sahel region. Assuming this persists through peak season, we should see robust tropical waves exit Africa, which have a better chance to develop into tropical cyclones.

Let's take a look at some climate models. While these models can be very inaccurate, there are two things I look for; consistency with each other and consistency with my forecast. Both of these are true this year. Essentially all climate models forecast an active hurricane season, which also fits with my forecast. They also all forecast a cool ENSO to some degree, as we expect to see.

Finally, let's talk about velocity potential (VP) anomalies, which show rising and sinking in the atmosphere. There is widespread sinking over the equatorial Pacific, clearly indicating a La Niña. There's strong rising motion over Africa, indicating an active WAM. There is sinking over the Central Atlantic, but it is much weaker than previous years due to the La Niña. It's expected to continue fading as we head into peak hurricane season.

So that's it for my forecast reasoning. Essentially all indicators point to a very active season. Assuming that the sinking over the Atlantic disappears, we could have an early start to peak season. I am not a meteorologist, so make sure to refer to official forecasts and information when making decisions. This will be my last forecast assuming there are no big changes that I want to discuss, so thank you for following along!