Talking the Tropics With Mike: 6th hurricane of the Atlantic season: Nicholas

Atlantic Basin remains active

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REMEMBER WHEN A TROPICAL STORM OR HURRICANE IS APPROACHING: Taping windows is *NOT* helpful & will not keep glass from breaking... & realize the cone is the average forecast error over a given time - out to 5 days - & *does not* indicate the width of the storm &/or damage therefore do not become fixated on the center of a tropical system.

The peak of the hurricane season is Sept. 10th with a mini peak in mid Oct.:

“Ida” summary in the “Buresh Blog” * here *.... past tropical systems similar to Ida * here *.

Areas to watch:

(1) Nicholas - moving over far SE Texas

(2) tropical waves headed west off the coast of Africa

(3) possible tropical development over the SW or W Atlantic later this week.

For right now, the Bermuda High across the Atlantic is displaced to the east & northeast - important for any potential long track tropical systems coming out of the deep tropics. *But* there are indications that the Bermuda High will shift back west & a little south while becoming stronger again as we head toward the last 10-12 days or so of Sept. This development will be key for a potential long track hurricane later this month.

(1) A tropical wave near & over Central America & the Yucatan Peninsula moved over the SW Gulf of Mexico Sun. morning & was upgraded to “Nicholas” becoming a hurricane late Mon. evening upon approach to the Central Texas Gulf Coast. If Nicholas stayed offshore just long enough & far enough, to “go” hurricane. Shear was moderate to strong but was also roughly aligned with the forward movement of Nicholas, so the storm still managed to gradually intensify. After landfall on the Central Southeast coast of Texas west/southwest of Galveston, Nicholas will slow dumping very heavy rain over far SE Texas eastward through much of Louisiana. Severe flooding is a concern along & to the east of the track of the storm’s track.

There will be no impacts on Jacksonville/NE Fl./SE Ga.

Nicholas is the 14th named storm of this busy hurricane season. From Dr. Phil Klotzbach: “Only 4 other years in satellite era (1966 onwards) have had 14+ named storms by 12 September: 2005, 2011, 2012, 2020″.

(2) Multiple tropical waves are marching west off the coast of Africa as one would expect near the peak of the season. A wave moving off the coast of Africa will move west this week with potential to become a tropical storm. This system could be a hurricane approaching the Caribbean mid to late next week - approximately Sept. 20-24th IF the Bermuda High strengthens & shifts west which would cause the wave to move more west vs. turning northward. Models are split on the turn north vs. a more west track.

(3) And forecast models continue to indicate *possible* tropical “activity” over or near the Western or SW Atlantic later this week. It looks like this development is being helped by an old tropical wave that moved off Africa days ago combined with an upper low. Forecast models have generally trended north on this disturbance to east of the Carolina’s (vs. east of Fl. the past week) though the low may start to consolidate east of Fl. but 200+ miles away from the coast while moving N/NW. The Outer Banks of N. Carolina could still be grazed by this system though the general trend has been more east during the past 24 hours. Something to keep a close eye on.

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.

September is historically the prime month for tropical cyclones across the Atlantic Basin:


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..... “Odette” 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 *.

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 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:

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:

“Chanthu” over the West Pacific is turning northeast while weakening:

Global tropical activity: