Tropical Storm Alex forms from the flooding Florida disturbance
The tropical disturbance that brought major flooding to Miami and the surrounding areas finally organized enough to be classified a tropical storm. The configuration of the upper-level winds changed just enough to let it form. Previously, they were ripping across the disturbance. That kept it from organizing, pushing the thunderstorms and tropical moisture well ahead of the surface circulation that kept trying to form. The upper winds also injected dry air into the system, which further gummed up the works.
The upper-level winds are still pushing on it, so that Alex is still seriously misaligned with a ragged surface circulation. But the National Hurricane Center analysis is that there is enough organization to classify it as a tropical storm.
Hurricane Hunters investigating that storm this morning found significantly stronger winds – now estimated at 60 mph. The system is not forecast to get much stronger as it passes near Bermuda tomorrow (Monday).
Shortly after that, the prediction is that Alex will be torn apart by the strong upper winds and die out in the middle of the Atlantic.
The floods in Miami and the surrounding areas were caused by a number of factors. Mainly, the strongest band of tropical thunderstorms wrapping around the disorganized disturbance tracked directly over the city and up the I-95 corridor in South Florida. Ten inches to more and a foot of rain fell, and a good part of it came all at once. Rain fell at a rate that would flood almost anywhere, at least temporarily. But other factors were involved.
Drenching thunderstorms pounded South Florida almost every day in the previous week, so the ground was quite saturated. That is, the water table was high. In much of Miami, however, the ground is covered by concrete – roads, buildings, parking lots, etc. So these days, there is very little green space to absorb the water. That means the drainage system has to work.
The drains in Miami, in general, flow into Biscayne Bay one way or the other. When the tide is low, they work efficiently. When the tide is high, the outflow is limited or stops.
Lately, the tides have been running significantly more than a foot higher than normal. This is caused by a number of factors including a persistent easterly wind pushing the ocean toward the coast. But it is also likely due to the slowing of the Gulf Stream, which is just offshore. This is being caused by complex factors related to global warming and the changing climate.
The powerful flow of water coming from the south bunches up and spreads out, including toward the Florida and East-Coast coastlines. It’s one of the factors behind the unusually high tides up and down the coast, though there are others.
The only solution is to build with these changes in mind. The City of Miami is studying the best way to do it. In Miami Beach, they have already installed new drainage systems in some neighborhoods, which remained high and dry during the deluge from the disturbance.
After Alex, it appears the tropics will remain calm for the rest of the week, at least.