The Atlantic soon to be unnamed – 104.5 WOKV
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October tropical cyclones:
” Sat ” :
The strong tropical wave – ’98 -L ‘- was improved on Wednesday. afternoon to tropical depression # 18 then tropical storm “Sam” Thursday morning and hurricane early Friday (the average date of the 7th Atlantic hurricane is November 16), So Sam has been a hurricane for over a week, but eventually calms down slowly over cooler water and under increasing shear. Sam was a compact / intense storm but recently ‘spread his wings’ while weakening. An early-game NOAA buoy measured seas 40 feet in the northeast quadrant of the hurricane! Although remaining far to the east, easterly swells and increased risk of a reverse current will affect much of the US east coast through Monday, including NE Fl./SE Ga. Bermuda were spared a direct hit as Sam’s core moved well to the east of the island Fri night.
As the system finally reaches the North Atlantic, Sam will become a large, strong extra-tropical ocean storm.
Ultimately … the end result – Sams’ trajectory – was driven by the readjustment in September of the upper level flow in the northern hemisphere, which included a fairly persistent trough in recent weeks above and close to the eastern United States and the western Atlantic. With the trough in place, the east coast of the United States is more or less protected … at least anything that grows far east over the Atlantic.
A strong tropical wave that has moved off Africa was upgraded to Tropical Depression # 20 Wed morning & to “Victor” Wed afternoon. The good news: – thanks to the Bermuda high sits so far north and east over the Atlantic – Victor turned strongly north as he quickly organized himself but has since fallen victim to a strong south and southwest shear. Victor will stay far east over the open Atlantic and dissipate.
Long-term forecasting models show the potential for some low to form over the West / SW Atlantic over the next week. We will have to watch this for possible tropical development. The first indications are that this minimum would be pulled north / northeast.
We will also need to monitor parts of the Caribbean and / or the Gulf of Mexico in the longer term.
(A thin cone means high forecast uncertainty):
Sam’s Spaghetti Plots:
An unfavorable MJO phase has generally helped to keep recent Atlantic tropical cyclones for the most part ‘under control’. There is a lot of “descending” air (brown lines) over the Atlantic basin which generally does not support much of tropical development (there may be exceptions!). * But * the rising air (green lines) will likely spread over the Atlantic as we move through October, leading to a potentially active 2nd to last month of hurricane season in the Atlantic. During this evolution we will need to monitor the Caribbean, the Gulf of Mexico and the southwest Atlantic where we are already getting occasional – albeit inconsistent – clues of tropical development from long-range models.
Ocean temperatures. staying “in shape” to help maintain tropical cyclones.
Sea surface temperatures across the Atlantic are now near above average. in much of the basin (2nd image below) and – even more importantly – the deep ocean heat content (which helped “feed” Ida and Sam) is impressive and the “equivalent ocean heat content”- namely the average temperature at depth in the upper 300 m (~ 984 feet) – is even more impressive from Africa to the Gulf of Mexico. Such a temperature of the ocean water. The model is conducive to long-trajectory deep tropical Atlantic tropical cyclones and may lead to a more favorable regime for cycles of rapid intensification. From an AMS research paper in ’08 Mainelli, De Maria, Shay, Goni: “The results show that for a large sample of Atlantic storms, variations in OHC have a small but positive impact on intensity forecasts. However, for intense storms, the effect of OHC is much more significant, suggesting its importance on the rapid intensification. The OHC input improved the mean intensity errors of the SHIPS forecast by up to 5% for all Category 5 storm cases, and up to 20% for individual storms, with the maximum improvement for the 72 forecast. -96 hours. The statistical results obtained indicate that the OHC only becomes important when it has values much higher than that required to withstand a tropical cyclone.. “More recent research continues to indicate similar correlations.
Saharan dust. Dry air – yellow / orange / red / pink. Widespread dust indicates dry air which can hamper the development of tropical cyclones. However, sometimes “wanna ‘be” waves will just wait to reach the other side of the plume and then try to develop if all else is right. In my opinion, we talk too much about the presence of Saharan dust and its link with tropical cyclones.
Names 2021 ….. “Wanda” is the next last name on the Atlantic list (names are randomly chosen by the World Meteorological Organization … repeat every 6 years … historic storms are removed (Florence and Michael in 18 … Dorian in ’19 & Laura, Eta & Iota in ’20). Last year – 2020 – had a record 30 named storms. WMO decided from this year that the Greek alphabet will no longer be used and instead there will be an additional list of names if the first list is exhausted (only happened twice – 2005 & 2020) Learn more about the history of the naming of cyclones tropical * here *.
Medium and high altitude windshear analysis (tropical cyclone enemy) (CIMMS). Red lines indicate strong shear:
Water vapor imaging (dark blue indicates dry air):
The heat content of the deep oceans continues to increase in the Gulf, the Caribbean and the tropical deep Atlantic and has become quite impressive from the central / northwestern Caribbean to the Gulf of Mexico:
Sea surface temperature. Anomalies:
Surface map of the SE of the United States:
Surface analysis centered on the tropical Atlantic:
Gulf surface analysis:
Forecast of GFS waves at 48 and 72 hours (2 and 3 days):
Forecast of the wave period of the Atlantic Basin for 24, 48 and 72 hours respectively:
The East Pacific:
West pacific Infrared satellite:
Global tropical activity:
Cox Media Group