Now that Barry has come and gone, what's in store for the next few weeks?
AccuWeather Chief Meteorologist Bernie Rayno explains the dates between which tropical storm activity goes into a quiet period each year – and why it happens. But don’t get lulled into a false sense of security.
Now that Barry, the first hurricane to make U.S. landfall this year, has come and mostly gone, what's in store for the next few weeks? Not too much, if the jet stream does what it usually does this time of year.
Each year, from around July 1 to mid-August, coastal states get a short window to catch their breaths as tropical activity goes into a quiet period. Those states can thank a variety of factors for these tropical season doldrums.
Storms form from two main ingredients: Tropical waves moving across the Atlantic and interactions between jet streams and the tropics.
The second factor, the interactions between jet streams and the tropics, is the catalyst behind many of the storms that form early in the season, from June to early July.
That interaction with the jet stream over the Gulf of Mexico sparked Tropical Storm Barry, which eventually made landfall as a hurricane, according to AccuWeather Chief Meteorologist Bernie Rayno.
It was a disturbance on the jet stream that was able to slowly spin down to the surface and gradually brew Barry.
However, by the latter half of July, the location of the jet stream typically changes and shifts north. The interaction that formed Barry would not occur in the middle to latter weeks of July because of that shift.
In the rest of the tropics, water temperatures are also below peak temperature, which assists in hampering storm development. However, the major factor behind this quiet period is the widespread availability of Saharan dust.
This water vapor satellite image shows the presence of dry air and Sahara dust over a swath of the Atlantic Ocean that makes conditions unfavorable for tropical development. (AccuWeather)
Because of the dryness carried by the dust-laden winds from Africa, many of the waves that come off African coasts are buffeted, thus preventing tropical development. Another contributing factor to the slow period is the strong wind shear in the tropics that is common in this season, Rayno explained.
But it's important to not get lulled into a false sense of security, as all of those factors change like clockwork starting mid-August and extending into September. During this time, water temperatures reach their peaks, wind shear lessens, and most importantly, the transport of Saharan dust is reduced significantly. From these factors, the entire Atlantic basin becomes a dangerous breeding ground for the development of tropical storms.
"There are regions of shear across the Atlantic basin this week, but the vertical wind shear is not as extensive as it was a couple of weeks ago," according to AccuWeather Hurricane Expert Dan Kottlowski.
"Indication are that wind shear will increase over the Caribbean and parts of the Gulf of Mexico into the end of July," Kottlowski said. "However, there will be large regions of low vertical wind shear over some sections of the basin. So, if the dry air and dust can become less extensive, environmental conditions could become more favorable for tropical development next week."
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