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The peak of the hurricane season was Sept. 10th with a mini peak in mid Oct. There is an overall concern regarding a rather late surge in Atlantic tropical activity & potential land impacts discussed in the “Buresh Blog” * here *.
Areas to watch:
(2) tropical waves Central & Eastern Atlantic
(1) Odette: low pressure over the Western Atlantic has developed into “Odette” - the 15th named storm of the Atlantic season. Only 3 other seasons have had as many storms by Sept. 17 in the satellite era - 2005, 2011 & 2020. Odette is very heavily weighted on the north & east side due to strong shear out of the southwest as the low resembles a subtropical or even post-tropical storm vs. a purely tropical cyclone. Odette has turned the corner to the northeast & will accelerate away from the U.S. through the weekend becoming post-tropical by late in the weekend while slowing not too far from Newfoundland where there will be strong winds & heavy rain Sunday into Monday. And there will be a heightened rip current risk on the New England coast through much of the weekend.
(2) Multiple tropical waves are marching west off the coast of Africa as one would expect near the peak of the season. Pockets of strong shear + some dry air will probably play a role in the intensity, but we’re likely to see a couple of tropical depressions/storms eventually develop. Positioning & strength of the Bermuda High will be critical on where these waves travel & how far west they manage to make it. At this point, it seems any systems over the next 10 days to 2 weeks will struggle to make it too far west within a somewhat marginal environment (sinking air) in addition to an alleyway (weakness/trough of low pressure) over the Western Atlantic. One of the lead waves - ‘95-L’ should be close to the Northeast Caribbean &/or Puerto Rico by the early to middle part of next week right before making the turn more northward. Obviously something to continue to track & monitor.
It is possible a period of heightened concern for U.S. impacts will evolve toward the end of the month & especially into Oct. - more on that potential *here* in the “Buresh Blog”.
The Bermuda High looks to stay displaced well to the north & east over the Atlantic while a sharp upper level trough moves into the Eastern U.S. Such a set-up should allow for an alleyway to remain over the Western Atlantic which would help turn strong tropical wave ‘95-L’ more northward once the wave/system is near the NE Caribbean & Puerto Rico.
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) 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..... “Peter” is the next 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 in 2021 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 *.
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 continues to increase across the Gulf, Caribbean & deep tropical Atlantic & has become pretty impressive 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:
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:
Cox Media Group