Wednesday, August 14th 2019, 7:30 pm - Looking to the past to explain 2019's hurricane season
We've made it to the middle of August and, so far, there have been only two named storms in the Atlantic hurricane season. While the average peak is still almost a month away, late August is when we typically expect to see the Atlantic Basin firing up.
Over the next week or so, however, the odds for any development seem slim. While it's not unusual for hurricane season to be slow to get started, this year's quiet streak is a bit out of the ordinary. We haven't had a named storm since July 14. If no named storm develops before August 19 -- and it doesn't look like one will -- it will be the first such stretch since 1982.
1982 is notable for a couple of reasons, weather-wise, but the biggest player on the field that year was a very strong El Niño phase active in the Pacific. Even though it's a phenomenon in the Pacific, El Niño has wide-reaching impacts, including disrupting winds over the Caribbean and Atlantic. Specifically, it increases wind shear over the region -- that is, the winds increase in speed with height. Hurricanes don't like this, as higher shear takes the developing storm's heat and energy and stretches it out over a broader range. That makes it harder for the storm to generate the strong convection that allows it to grow.
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While we did have a relatively weak El Niño in the Pacific earlier in 2019, it returned to a neutral phase in July. That neutral phase is expected to persist through the winter, according to NOAA. This may open the door to more development -- and may have encouraged NOAA to up its forecast for the number of storms expected to develop this year -- but strong wind shear is still present across the central Atlantic.
Another factor impeding development at the moment is hot, dry air from the Sahara drifting out across what is typically the main development region for tropical cyclones over the Atlantic. As above with the wind shear, hurricanes need a tall column of hot, but moist, air to support the convection that turns them into massive storms. This hot, dry layer -- you can see it on the sounding chart below as a bulge in the red temperature line, the bottom of the chart is the surface and measures temperature and dewpoint with height -- is effectively putting a cap on convection at the moment.
So, if we're off to a similar start, how did 1982 finish up?
1982 had six tropical cyclones in the Atlantic, five of which were named storms, including two hurricanes. As noted above, most of these were peak-to-late season storms, with two systems forming in June, and then a lull that lasted until August 28.
Does that mean we're in for the same this year? Not necessarily. For one, 1982's El Niño event lasted all the way into 1983 hurricane season and, as we've seen, the most recent event just ended. There are some signs that 1982 had higher-than-average Sahara dust concentration, as well, but that in and of itself isn't a determiner for how the rest of the season will play out.
Since the set-up isn't identical, it's hard to use 1982 as a real analog year, but one thing does seem likely when it comes to this year -- we probably haven't seen the worst the Atlantic Basin has to offer yet.