Theta satellite image
Visible satellite image of Subtropical Storm Theta at 10:35 a.m. EST November 10, 2020. (Image credit: Tropical Tidbits)

A record many thought unassailable has fallen: the Atlantic named storm record of 28 storms in a season, set during the hellish hurricane season of 2005. On Monday night, the ridiculously prolific 2020 hurricane season spawned its 29th named storm, Subtropical Storm Theta, beating the old record from 2005. There is still plenty of time for 2020 to add to its record tally, and a tropical wave in the Caribbean is likely to become the 30th named storm of the season, Tropical Storm Iota, by this weekend. The average tally of Atlantic named storms in a season is just 12.

Figure 1
Figure 1. The record Atlantic hurricane season of 2020, compared to 2005 and to average. One of 2005’s storms was recognized only in post-season analysis and was never named, so both Eta and Theta were used in 2020 for the first time. (Image credit: Sam Lillo)

Theta’s formation, in conjunction with Tropical Storm Eta’s continued presence in the Gulf of Mexico, gave the Atlantic two simultaneous named storms on November 10 – a very rare occurrence in November. According to Dr. Phil Klotzbach of Colorado State University, the last time the Atlantic experienced two named storms this late in the year was on November 10, 1932. The latest in the calendar year that the Atlantic hurricane season has had two named storms simultaneously was in December 1887.

Theta little threat to land

At 10 a.m. EST Tuesday, Theta was located about 860 miles southwest of the Azores Islands, headed east at about 15 mph. Theta had top sustained winds of 70 mph, just below hurricane strength. Satellite images showed Theta still had characteristics of a subtropical storm, but it is expected to become fully tropical by Tuesday night.

Theta had seemingly unfavorable conditions for development, with sea surface temperatures (SSTs) near 25 degrees Celsius (77°F), high wind shear of 50 – 60 knots, and a dry atmosphere with a mid-level relative humidity of 45%. However, Theta had highly favorable levels of atmospheric instability, created by very cold temperatures in the upper atmosphere (minus 58 degrees Celsius at 200 mb, about five degrees Celsius colder than what Tropical Storm Eta is currently experiencing). This mix of factors often is found in late-season tropical storms.

Bob Henson tweet

Theta will move in an east to east-northeast motion through the end of the week, taking the storm between the Azores Islands and Canary Islands toward Portugal (see the Tweet from Bob Henson, with last night’s forecast track for Theta). The only land area in Theta’s five-day cone of uncertainty is Portugal’s Madeira Island, which could experience tropical storm conditions on Saturday and Sunday. High wind shear and cold waters are expected to weaken Theta to a post-tropical cyclone with 40 mph winds by Sunday.

Not one Iota more, please!

A tropical wave in the eastern Caribbean (designated 98L by the National Hurricane Center on Tuesday morning), is expected to merge with a larger area of low pressure in the central Caribbean late this week. The top three models for predicting tropical cyclone genesis were giving 98L strong support for development by this weekend, when the wave will likely be in the central or southwestern Caribbean, between Jamaica and Nicaragua. The wave is predicted to move westward to west-northwestward under the steering influence of a ridge of high pressure to its north, resulting in a potential threat to Jamaica, the Cayman Islands, and Central America this weekend. Conditions for development will mostly be favorable this weekend, with the SHIPS model predicting moderate wind shear of 10 – 20 knots and warm SSTs of 29 degrees Celsius (84°F). However, some dry air in the western Caribbean may interfere with development.

In a 1 p.m. EST Tuesday Tropical Weather Outlook, NHC gave 98L two-day and five-day odds of development of 10% and 70%, respectively. The next name on the Atlantic list of storms is Iota, the ninth letter in the Greek alphabet.

Figure 2
Figure 2. GeoColor satellite image of the Atlantic at 10:20 a.m. EST Tuesday, November 10, 2020. (Image credit: RAMMB/CIRA/Colorado State University)

Eta meandering in the Gulf of Mexico

Tropical Storm Eta, which made landfall in the Florida Keys with sustained winds of 65 mph on Sunday night, has parked itself over the southeastern Gulf of Mexico, just northwest of the western tip of Cuba. At 10 a.m. EST Tuesday, the nearly stationary Eta had top winds of 60 mph and a central pressure of 992 mb.

Rainbands from Eta set up over portions of southern and central Florida over the past three days, resulting in torrential rains that caused widespread urban flooding. The heaviest rains, in excess of a foot, fell in Broward County, where Fort Lauderdale is located. Some top 72-hour rainfall amounts reported by the National Weather Service for Florida, as of 7:41 a.m. EST Tuesday, November 10:

16.04 inches, Miramar;
12.27 inches, Plantation;
9.53 inches, Fort Lauderdale;
8.16 inches, Pembroke Pines;
6.87 inches, Miami; and
5.96 inches, Miami Beach.

Eta is expected to bring an additional 1-2 inches of rain to South Florida though Wednesday, and 3-5 inches to western Cuba.

Forecast for Eta

Also see: How climate change is making hurricanes more dangerous

Eta will have mostly favorable conditions for intensification through Thursday, with moderate wind shear of 10-15 knots and SSTs near 28.5 degrees Celsius (83°F). However, Eta is embedded in a dry atmosphere with a mid-level relative humidity of 50%, and this dry air will potentially put the brakes on any rapid intensification.

Figure 3
Figure 3. Track forecasts out to six days for Eta from the 6Z (1 a.m. EST) Tuesday, November 10, run of the GFS ensemble model (GEFS). The black line is the mean of the 31 ensemble members; individual ensemble member forecasts are the thin lines, color-coded by the central pressure they predicted for Eta. The long-term motion of Eta was highly uncertain. (Image credit: Tropical Tidbits)

Steering currents are weak over the Gulf of Mexico, but a trough of low pressure passing to the north of Eta is expected to begin pulling the storm to the north by Tuesday night, with the storm continuing a slow northerly motion at less than 5 mph through Friday. Beyond Friday, there is much disagreement among the models on the future track of Eta, and the default cone of uncertainty depicted on the official forecast is likely too small. The GFS model, which keeps Eta weak, suggests the storm will move mostly westward with the low-level flow. The European model predicts that Eta will be stronger, and move more to the north, steered more by the upper-level winds. In either case, Eta will be encountering cooler waters and higher wind shear late this week and continued incursions of dry air. These unfavorable conditions should cause weakening, and Eta may become a tropical depression by Sunday.

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Posted on November 10, 2020 (2:35pm ET).

Jeff Masters, Ph.D., worked as a hurricane scientist with the NOAA Hurricane Hunters from 1986-1990. After a near-fatal flight into category 5 Hurricane Hugo, he left the Hurricane Hunters to pursue a...

33 replies on “Theta forms in the Atlantic, breaking record as 29th named storm of the 2020 Atlantic hurricane season”

  1. We get the point man. Jesus. Your username lends you garbage credibility, no need to comment 47 times in 15 minutes that your shower curtain weather studio in the basement predicts a non-event.

      1. People will always talk about the weather, but that group of individuals on Cat6 in the late Aughts will never be replicated.

  2. Looks like Eta will cross central Florida and make it to the East Coast. It will be interesting to see how much energy / structure holds on. Land and wind shear should start breaking up the storm.

    Now that Eta is approaching its end; does anyone have projections on it’s total ACE and total active days? It must be close to a record…..

  3. Tropical Storm Eta Local Statement Advisory Number 44
    Tropical Storm Eta Local Statement Advisory Number 44
    National Weather Service Tampa Bay Ruskin FL  AL292020
    445 AM EST Wed Nov 11 2020
    This product covers West Central and Southwest Florida
        - A Tropical Storm Warning has been issued for Polk
        - A Hurricane Watch has been issued for Coastal Citrus, Coastal
          Hernando, Coastal Hillsborough, Coastal Levy, Coastal Manatee,
          Coastal Pasco, and Pinellas
        - A Tropical Storm Warning is in effect for Inland Citrus, Inland
          Hernando, Inland Hillsborough, Inland Levy, Inland Manatee,
          Inland Pasco, Inland Sarasota, Polk, and Sumter
        - A Tropical Storm Warning, Storm Surge Watch, and Hurricane
          Watch are in effect for Coastal Citrus, Coastal Hernando,
          Coastal Hillsborough, Coastal Levy, Coastal Manatee, Coastal
          Pasco, and Pinellas
        - A Tropical Storm Warning and Storm Surge Watch are in effect
          for Coastal Charlotte, Coastal Lee, and Coastal Sarasota
        - About 180 miles southwest of Fort Myers FL
        - 25.0N 84.1W
        - Storm Intensity 70 mph
        - Movement North or 10 degrees at 12 mph
    1. Hey Art. Hope you’re ready. Go to bed last night breathing easy and this morning having to prepare for Eta. We got dumped on late last night about 1:30. Woke the house. That track looks like you first then right over us.. Be safe.

  4. Japan Meteorological Agency
    Tropical Cyclone Advisory #23 – 15:00 PM JST November 11 2020
    Sea East of the Philippines

    At 6:00 AM UTC, Typhoon Vamco (970 hPa) located at 14.4N 123.5E has 10 minute sustained winds of 70 knots with gusts of 100 knots. The cyclone is reported as moving west at 10 knots.

    Storm Force Winds
    60 nm from the center

    Gale Force Winds
    240 nm from the center in northern quadrant
    150 nm from the center in southern quadrant

    Dvorak Intensity: T4.0

    Forecast and Intensity
    12 HRS: 15.2N 121.4E – 80 knots (CAT 3/Strong Typhoon) Over land Aurora province (Luzon/Philippines)
    24 HRS: 15.5N 118.6E – 65 knots (CAT 3/Strong Typhoon) South China Sea
    48 HRS: 15.3N 114.5E – 65 knots (CAT 3/Strong Typhoon) South China Sea
    72 HRS: 15.7N 110.5E – 60 knots (CAT 2/Severe Tropical Storm) South China Sea

  5. Its incredible that we have surpassed the 2005 Atlantic Hurricane Season in terms of number of storms. I never thought I would see anything like the 2005 Atlantic season again in my lifetime.

    My latest birdseye view chart and post of the Atlantic tropics is at this link. I think Eta has a shot at approaching the west coast of Florida as a strong tropical storm or hurricane if it doesn’t track too far north into upper westerly shearing winds over the next few days. Eta is like a pest that won’t go away.

  6. Japan Meteorological Agency
    Tropical Cyclone Advisory #21 – 9:00 AM JST November 11 2020
    Sea East of the Philippines

    At 0:00 AM UTC, Typhoon Vamco (975 hPa) located at 14.6N 124.6E has 10 minute sustained winds of 65 knots with gusts of 95 knots. The cyclone is reported as moving west at 10 knots.

    Storm Force Winds
    60 nm from the center

    Gale Force Winds
    240 nm from the center in northern quadrant
    150 nm from the center in southern quadrant

    Dvorak Intensity: T4.0

    Forecast and Intensity
    12 HRS: 14.8N 122.9E – 70 knots (CAT 3/Strong Typhoon) Sea East of the Philippines
    24 HRS: 15.3N 119.6E – 55 knots (CAT 2/Severe Tropical Storm) South China Sea
    48 HRS: 15.2N 115.8E – 65 knots (CAT 3/Strong Typhoon) South China Sea
    72 HRS: 15.4N 111.7E – 70 knots (CAT 3/Strong Typhoon) South China Sea

  7. I cosine Bob Henson’s clever quote. Clearly, an integral part of the conversation.Nothing derivative about Bob’s remarks. There is no limit to his functions.His transformation of feasible solutions is exponential.His permutations and combinations are endless.The probability of his success is not conditional. Finally, he can differentiate Pascal’s triangle from the Bermuda triangle.In short, a genius.

  8. I have to sort of commend everybody for bearing with this unusual event, are we at 29 or 30 named storms so far?

    The Spanish weather people are very excited by all this and of course the storm Theta is moving in the north east direction, so that makes them even more “excited!”
    In reality, is this late season east to easterly north direction something we must now take note of and possibly consider as a new, or newer alternative direction for storms and possible future hurricanes?
    Who’s to say at this point but we have postulated this scenario for a while now, maybe within the next 20 to 50 years the Atlantic season will be a lot more diverse than it has been in “recorded history.”

  9. MASHA DANKI (thank you)……for the new post. Parts of my semi arid Island have turned into flood plains. The wildlife is happy & the frogs are Sooo loud at night. As for me though, really don’t want another season like this but with some reports of La Niña continuation for 2021…..adapt or be grumpy!

  10. This season has been absolutely unreal with the amount of named storms, the several that have made landfall in the norther Gulf of Mexico… I wonder how typical this season will become as we look back on it years from now.

  11. Thanks for this new post, Dr. Masters.
    I fervently hope we don’t have any more deadly or destructive storms this year. I’m ready to read you on human-caused climate change again. That serious problem has gotten worse these last few years. I’m looking forward to hearing your thoughts on that.
    For now, though, it helps so much to have your and Bob Henson’s discussions when we do have storms to watch or contend with.

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