Buresh Blog: Tropics *Still* the Topic!... Seasonal Warming... “Gargantuan” Hail in Libya

Buresh Blog: Tropics *Still* the Topic!... Seasonal Warming... “Gargantuan” Hail in Libya

Jacksonville Fl. — Talking the Tropics With Mike” - updated every day during the hurricane season.

The tropics continue to roar right into Nov. The “ACE” - Accumulated Cyclone Energy is a good measure of how active a hurricane season is by taking into account duration & intensity. In simple terms: the higher the ACE, the more active the season. Through Nov. 11th, the 2020 Atlantic Base Ace was at 163 - “extremely active”. In technical terms the definition of ACE according to NOAA:

The phrase “total overall seasonal activity” refers to the combined intensity and duration of Atlantic named storms and hurricanes occurring during the season. The measure of total seasonal activity used by NOAA is the Accumulated Cyclone Energy (ACE) index. The ACE index is a wind energy index, defined as the sum of the squares of the maximum sustained surface wind speed (knots) measured every six hours for all named storms while they are at least tropical storm intensity.

Content Continues Below

The 1981-2010 mean value of the ACE index is 105.6 x 104 kt2, and the median value is 92.4 x 104 kt2. The following classifications are based on an approximate tercile partitioning of seasons based on the ACE index, combined with the seasonal number of tropical storms, hurricanes and major hurricanes.

Extremely active season: An ACE index above 152.5 x 104 kt2 (corresponding to 165% of the 1981-2010 median).

Above-normal season: An ACE index above 111 x 104 kt2 (corresponding to 120% of the 1981-2010 median), with at least two of the following three conditions: 13 or more named storms, 7 or more hurricanes, and 3 or more major hurricanes.

Below-normal season:

  • a) An ACE index below 66 x 104 kt2 (corresponding to less than 71.4% of the 1981-2010 median), or
  • b) An ACE index above 71.4% of the median with the following three conditions: 9 or fewer named storms, 4 or fewer hurricanes, 1 or fewer major hurricanes.

Near-normal season: Neither the above- nor below-normal season criteria are met.

A near-normal season will typically have an ACE range of 66-111 x 104 kt2 (corresponding to 71.4%-120% of the 1981-2010 median).

Another pretty remarkable stat: at least one named storm has made a U.S. landfall every month from May through November!

One of the most recent storms - “Eta” developed Oct. 31st & hit Nicaragua as a Cat. 4 hurricane then turned northeast & moved across the Caribbean moving across Cuba then the Fl. Keys & eventually the Big Bend of Fl. moving northeast over Jacksonville Thu. afternoon before moving over the Western Atlantic. As of this writing - Thu. evening, Nov. 12 - the tropical storm was just off the coast of S. Carolina. Eta made 4 landfalls (Nicaragua/Cat. 4... Cuba/T.S.... Keys/T.S.... Cedar Key/T.S. It’s the first Fl. Nov. landfall by a named storm since a rather infamous “Gordon” in 1994 which looped across Fl. making 3 different landfalls.

Eta now joins three other tropical cyclones whose center moved through at least a part of Duval Co. since 2000 - Julia in 2016, Beryl in 2012 & Tammy in the infamous season of 2005.

Fl. rainfall from Eta (by FPREN):

Remember to take a look up at the nighttime sky Nov. 16-17 for the peak of the annual Leonid meteor shower renowned for some of the best meteor showers we ever see. From the American Meteor Society:

Next period of activity: November 6th, 2020 to November 30th, 2020

The Leonids are best known for producing meteor storms in the years of 1833, 1866, 1966, 1999, and 2001. These outbursts of meteor activity are best seen when the parent object, comet 55P/Tempel-Tuttle, is near perihelion (closest approach to the sun). Yet it is not the fresh material we see from the comet, but rather debris from earlier returns that also happen to be most dense at the same time. Unfortunately it appears that the earth will not encounter any dense clouds of debris until 2099. Therefore when the comet returns in 2031 and 2064, there will be no meteor storms, but perhaps several good displays of Leonid activity when rates are in excess of 100 per hour. The best we can hope for now until the year 2030 is peaks of around 15 shower members per hour and perhaps an occasional weak outburst when the earth passes near a debris trail. The Leonids are often bright meteors with a high percentage of persistent trains.

Shower details - Radiant: 10:08 +21.6° - ZHR: 15 - Velocity: 44 miles/sec (swift - 71km/sec) - Parent Object: 55P/Tempel-Tuttle

Next Peak - The Leonids will next peak on the Nov 16-17, 2020 night. On this night, the moon will be 5% full.

Image Credit: NASA/Ames Research Center/ISAS/Shinsuke Abe and Hajime Yano

Seasonal warming - since about 1970 - has been occurring across most of the U.S. The same can be said for Florida, especially the winter as the avg. temp. across the state has increased a little more than 3 degrees F according to “Climate Central”. Even more telling - the number of Jacksonville (JIA) freezes the last 10 winters. The long term avg. is 18 freezes (inland) per winter, but we have not had more than avg. number of freezes since 3 back to back winters from 2008 - 2011. Going back to 2012, the avg. has been cut in half - only 9 inland freezes per winter. The last few winters have been especially mild (low number of inland freezes with virtually no freezes closer to the coast & the beaches).

Lastly.... crazy video out of Libya where “gargantuan” hail occurred near the end of Oct. Libya has a desert climate averaging less than a foot of rain per year but will get occasional thunderstorms. An especially intense super cell t’storm hit Libya dropping hail near 7″ in diameter! The video (sound up!) is something to see - * here *. Mateusz Taszarek pic of one of the big hailstones: