A big plume of dust from the Sahara Desert has blown off the African coast and is spreading across the Atlantic. The dust has the effect of drying out the atmosphere several thousand feet up. Where that dry air spreads, tropical formation is less likely. It’s fairly typical to get Saharan Dust outbreaks in June and July.
Separately, a large non-tropical low-pressure system is trying to form in the middle of the Atlantic east of Bermuda. There’s a slight chance it will sit out there long enough to become at least somewhat tropical. It’s well north of where the dust will spread. Even if the low does develop some tropical characteristics, it wouldn’t last long, and will move out to sea.
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Indirectly, that low-pressure system will affect South Florida, however. The low is connected to a front, which is the leading edge of dry air being pulled down from farther north in the Atlantic.
That dry air will push into South Florida about Thursday, which will finally push out the soupy tropical air that’s been blanketing us since before Tropical Storm Cristobal moved by. The atmosphere should be noticeably more comfortable at the end of the week.
Cristobal is still a pretty healthy system, though its winds have decreased, officially making it a tropical depression. It’s now moving north across the Midwest. Wind alerts are in effect across the western Great Lakes, Illinois and surrounding areas. By tomorrow, the center of circulation will be in Canada, and the system will merge with a northern low-pressure system.
Cristobal’s legacy is a flood threat along the Mississippi River and surrounding rivers and creeks caused by the storm’s heavy rain. The threat will continue until the water is able to drain.
Elsewhere, there are no signs of trouble.