Talking the Tropics With Mike: Unseasonably quiet Oct. so far

Strong cold front diving south into the Gulf/SW Atlantic

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No areas of concern across the Atlantic basin as a good deal of shear - a hallmark of autumn - dominates much of the Atlantic Basin... for now. A strong cold front has pushed far to the east over the Atlantic extending southwest through the Bahamas to near Cuba then west across the far Southern Gulf of Mexico. This front is becoming stationary, & we’ll watch this front for possible low pressure development through the upcoming weekend.

Friday was the first time there has not been an area highlighted somewhere across the Atlantic since Aug. 2nd!

An unfavorable MJO phase over the Atlantic Basin is only slowly changing/evolving (see map below). There has been a lot of “sinking” (brown lines) air over the Atlantic Basin which doesn’t usually favor a good deal of tropical development (there can be exceptions!). *But* the rising air (green lines) has been forecast to overspread the Atlantic as we move through Oct. into early Nov. which would lead to a potentially more active late season over the Atlantic. During this evolution, we’ll need to monitor the Caribbean, Gulf of Mexico & SW Atlantic. I would be very surprised if we don’t have at least one more named storm to deal with though the basin is very quiet right now (as are all the global basins!).

Ocean temps. remain “fit” to help maintain tropical cyclones.

Sea surface temps. across the Atlantic are now near to above avg. across much of the basin (2nd image below) & - even more importantly - deep oceanic heat content (which helped “feed” Ida & Sam) is impressive & the “equivalent oceanic heat content” - namely depth averaged temperature in the upper 300 m (~984 feet) - is even more impressive all the way from Africa to the Gulf of Mexico. Such an ocean water temp. pattern is conducive to long track deep tropical Atlantic tropical cyclones & can lead to a more favored regime for rapid intensification cycles. From an AMS research paper in ‘08 Mainelli, DeMaria, Shay, Goni: “Results show that for a large sample of Atlantic storms, the OHC variations have a small but positive impact on the intensity forecasts. However, for intense storms, the effect of the OHC is much more significant, suggestive of its importance on rapid intensification. The OHC input improved the average intensity errors of the SHIPS forecasts by up to 5% for all cases from the category 5 storms, and up to 20% for individual storms, with the maximum improvement for the 72–96-h forecasts. The statistical results obtained indicate that the OHC only becomes important when it has values much larger than that required to support a tropical cyclone.” More recent research continues to indicate similar correlations.


Saharan dust. Dry air - yellow/orange/red/pink. Widespread dust is indicative of dry air that can impede the development of tropical cyclones. However, sometimes “wanna’ be” waves will just wait until they get to the other side of the plume then try to develop if everything else happens to be favorable. In my personal opinion, way too much is made about the presence of Saharan dust & how it relates to tropical cyclones.

2021 names..... “Wanda” is the next & last name on the Atlantic list (names are picked at random by the World Meteorological Organization... repeat every 6 years... historic storms are retired (Florence & Michael in ’18... Dorian in ’19 & Laura, Eta & Iota in ‘20). Last year - 2020 - had a record 30 named storms. The WMO decided beginning this year that the Greek alphabet will be no longer used & instead there will be a supplemental list of names if the first list is exhausted (has only happened twice - 2005 & 2020). More on the history of naming tropical cyclones * here *.

East Atlantic:

Mid & upper level wind shear (enemy of tropical cyclones) analysis (CIMMS). The red lines indicate strong shear:

Water vapor imagery (dark blue indicates dry air):

Deep oceanic heat content over the Gulf, Caribbean & deep tropical Atlantic & remains pretty impressive late in the season from the Central/NW Caribbean into the Gulf of Mexico:

Sea surface temp. anomalies:

SE U.S. surface map:

Surface analysis centered on the tropical Atlantic:

Surface analysis of the Gulf:

Caribbean:

GFS wave forecast at 48 & 72 hours (2 & 3 days):

Atlantic Basin wave period forecast for 24, 48 & 72 hours respectively:

The East Pacific:

West Pacific IR satellite:

Global tropical activity: