It’s that time of year again. June marks the official start of the Atlantic hurricane season, and forecasters are predicting an above average year. Early season forecasting has predicted 16 named storms and eight hurricanes, compared to the historic average of 12.1 named storms and 6.4 hurricanes.
What do these numbers mean? Colorado State University’s Jhordanne Jones breaks down the forecasting released by CSU’s Tropical Meteorology Project and how scientists evaluate environmental conditions to form their predictions.
The next CSU hurricane season forecast will be released on Thursday, 4 June.
Partial podcast transcript:
Cayman Compass: To start off, can you just give me some background on the forecasting that CSU does? What are you guys looking at? How do you come up with your forecasting?
Jhordanne Jones: So, Colorado State University supplies seasonal hurricane forecasts as early as early April, which is our extended forecast. And then a forecast for early June, early July, and then early August. All of these forecasts essentially try to give us an estimation of the overall hurricane activity that we’re likely to see in the north Atlantic.
These forecasts are based on both current and future estimates of environmental conditions. So, it will take into account what the current sea surface temperatures are, what the state of winds above the north Atlantic are, and what commonly known climate indices are also doing at this point in time.
And just to name a few, that’s like the El Niño Southern Oscillation, or ENSO for short. There’s also the Atlantic Multidecadal Oscillation, which is a combination of sea surface temperatures and sea level pressure. Those are things that give us this indication of how favourable the environment is for hurricane activity.
CC: I was going through the April forecast, which is the latest you have out right now and that’s the earliest of the season, right? …
There were some terms that kind of went over my head, and I’m sure the general public might not fully grasp either, getting into the El Niño La Niña conditions this year.
Can you break that down for me and explain what we’re seeing with those effects?
JJ: Sure. So, just to back up a little to Meteorology 101, the El Niño Southern Oscillation is essentially this large pool of either warm or cold waters in the equatorial Pacific and it is a huge driver or influence on basically just about any atmospheric phenomena that you can think of along the tropical belt.
So, if you’re talking about Central America, the Caribbean, that tropical part of Africa, it affects everything and it even has connections to other climate phenomena further away from the equator. So, it’s this huge, huge impact on our region. With ENSO, you have either an El Niño event, a neutral event or a La Niña event. The El Niño event is when you have really warm waters in the Pacific and a La Niña event is when you have really cold waters in the Pacific. And then neutral is just when it’s tepid, right? It’s really neutral. It’s neither hot nor cold and probably won’t have much of an impact.
So, when you have like really warm waters or really cold waters, it tends to influence the winds just above it, so it can change the direction of winds over the North Atlantic and generally for an El Niño event in the Pacific, you’re very likely to have winds that oppose hurricane motion coming towards us.
With a La Niña event, where you have cold waters over the Pacific or in the Pacific, then you tend to have winds that go along with hurricane activity. So, it doesn’t impede hurricane activity as much, and we’re very likely to see way more hurricane activity than in other phases of ENSO.
What we’re currently seeing now is that the Pacific is what you’d call tepid. It’s near neutral. It’s warm but it seems to be trending downwards towards colder waters and the probabilities for it being either neutral or a weak La Niña, that it’ll be slightly cold, is far greater than the probability or the likelihood that it would be warmer.
So, because of that, most experts are anticipating that we will have above-normal hurricane activity.
If we have warm Atlantic sea surface temperatures, then there’s more fuel for hurricane activity, which means if the Atlantic is really warm, then we’ll definitely, or we’ll more than likely see more hurricane activity. It’s a combination of warm sea surface temperatures in the Atlantic and relatively cold sea surface temperatures in the Pacific.
CC: All right, so when you say we’re anticipating an above-average season, what does that look like? What are forecasters anticipating right now?
JJ: Above normal activity is pretty much anything above 10 named storms Our estimates are showing around 16 named storms for 2020.
So, that is pretty above average. Also for an average season, you’d expect around two to three hurricanes or major hurricanes. We are anticipating four major hurricanes along with eight hurricanes. So, that is actually a pretty active season.
And just to put that into like a visual context, that’s pretty close to what we’ve seen for 2017, 2018, 2019. So, yeah, we’re seeing that kind of activity or are anticipating that kind of activity.