September 10 is regarded as the peak of the Atlantic hurricane season and today is no exception. We have Leslie, Michael and a new tropical depression forming in the east Atlantic which should go on to become tropical storm Nadine.
The only system that will affect land is Leslie. Top winds are still below hurricane strength but Leslie is such a large storm that its effects will reach Newfoundland well ahead of the center. In fact, the center is of little consequence due to the general lack of an inner core. The wind field is spread out over a very large area and this means tropical storm force winds or higher will spread in to the region and last for several hours. Leslie will also bring heavy rains to the area but at least it will be moving quite quickly.
It is interesting to note that the 5-day NHC forecast map shows the remnants of Leslie passing very close to Iceland, of all places, by day 5. By then, the storm will be transitioned from a warm-core cyclone to one that has its energy spread over a wide area with a more or less level temperature throughout. Tropical cyclones are warmer the closer to their centers you get. I think this is a great example of how tropical cyclones remove heat from the tropics and disperse it towards the poles.
Elsewhere, hurricane Michael continues to churn along at a high latitude with winds near 80 mph this morning. It is forecast to eventually turn north and northeast and should not pose any problems to land areas. However, its energy will also translate north in to the far reaches of the North Atlantic, perhaps reaching portions of Europe before all is said and done.
Then we have invest 91L which is likely to become tropical storm Nadine later this week. No worries about this system as the pattern currently in place does not favor significant westward tracks of eastern Atlantic tropical cyclones. I think that we will not see any threats to the U.S. or Caribbean until after the 20th of the month when the pattern begins to change some. This is a natural evolution in the season as development areas shift from the deep tropical Atlantic towards the western Atlantic and the Caribbean Sea. If we factor in the non-event that the growing El Nino has turned out to be, then I believe we can expect a fairly active late September and early October. For now, with the exception of Leslie, none of the existing tropical systems will impact land areas.