A tropical system may affect Florida, Alabama, and other parts of the Gulf Coast between late this week and early next week, potentially causing heavy rains and gusty winds. It's one of three tropical wave forecasters being tracked, and it has the best chance of the trio developing.
Possible Brewing Storms for the Gulf of Mexico
A tuft of showers and thunderstorms blaze across the southeastern Bahamas in the north from Haiti. It will shuffle north in the next few days and pass areas that Dorian hit hard on Friday. It could shower Grand Bahama and Abaco with one to three inches of rain.
From there, the Florida fault visits the peninsula late this week until early Saturday, crossing the peninsula and dropping up to several inches of rain before possibly returning to the Gulf.
By crossing the warm Gulf waters, the young system could consolidate and organize some this weekend. If this is the case, the disturbance does not have much time over the warm Gulf waters. How lively she can become is limited by her short development window. However, it is becoming more and more likely that a tropical storm will develop. The National Hurricane Center estimates this rate at 60 percent. The next name? Humberto.
The extent of the disruption is uncertain, but the encouraging news is that its short lifespan makes it unlikely that the strength of a hurricane will be reached. Instead, it could be one of those sneaky systems that causes drenched rainfall.
After overflowing from Florida, Louisiana, Mississippi and Alabama are the locations where heavy rainfall may occur between Sunday and Tuesday. Where the porthole settles, it is likely that some locations will see up to half a foot of rain. The European model (see below) is currently showing Alabama, but this could shift west or east if this forecast becomes more prominent. The American model (not shown) simulates the heaviest rainfall in Mississippi and southeast Louisiana.
The risk to states along the eastern Gulf of Mexico has risen compared to the west. The models had problems with their "initialization" on Tuesday, putting the center of the lows in the wrong position. This led to a worsening tracking error over time. Now that models are more specific to the position of the disturbance, they tend to point eastward in their forecasters, where this system will end up when it gets into the Gulf.
Some of them are ] welcoming this potential system and calling it a much-needed drought buster. At least a quarter of Alabama is in a kind of drought, a number that has risen.
Disruption near the Lesser Antilles
Much further east in the tropical Atlantic is a "large but disorganized area with clouds and thunderstorms," located about 650 miles east of the Lesser Antilles. Despite its size, the system lacks the necessary momentum to turn into a cyclone. In addition, the environment will be hostile to their development. The National Hurricane Center writes that "this system will move westward towards unfavorable winds at higher altitudes for the formation of tropical cyclones". It has no more than 10 percent development probability per center.
Disruption off the West Coast of Africa  Wednesday morning an additional disturbance occurs in western Africa. (NOAA / RAMMB)
This last supervised tropical weather system is a lump between the Cape Verde Islands and the west coast of Africa. In the short term, the atmospheric conditions do not favor its development.
The National Hurricane Center estimates it has a 20 percent chance of strengthening over the next five days. However, there is evidence that this wave could attempt to merge into a more organized low pressure zone within about six to ten days. This, together with more promising areas of rising air over the Atlantic Basin, may increase the chances of developing thereafter. However, this is a long way. At present, it is best to call it a "wait and see" disorder.
Extended Discussion: The Next Increase in Hurricane Activity
Nearly half a dozen systems have tried to evolve since Dorian failed. However, a return to dangerous activities is possible. Using tropical meteorology, we can estimate a return to an active pattern from approximately the following dates (within a few days):
Gulf of Mexico: Sept. 19
Caribbean: Sept. 21  Tropical Atlantic: Sept. 25
Why? It has something to do with something called Madden-Julian Oscillation or MJO.
The MJO is a large overturning circulation that spreads about 48 km / h in an easterly direction over the globe. In practice, it is just a huge, slow, invisible wave that lifts the air to the west and lowers it to the east. At the leading edge of these waves is the "suppressed" phase of the sinking of air. In the west (at the back of the shaft) the air is more prone to climbs – favorable for hurricane activity.
You can see it here. Pay attention to the areas brown and green. Notice what happens in phases 1, 7 and 8. You see a lot of green on the other side of the Atlantic. This points to ascending air:
Now we can look at what weather models the MJO is estimated to do. Almost all models indicate a return to Phase 1 or 8, the phase that favors hurricane activity across the Atlantic within the next two to three weeks. The upward movement would first come from the west across the Gulf of Mexico before dodging the rest of the tropical Atlantic.
In addition, there is another mechanism – a convectively coupled Kelvin wave – located in the larger MJO shell and causing the same. This, too, will help promote hurricane production in late September to early October.
Even though Dorian looks calm, it will not take long.