Honduras flooding
The CA-5 highway between Pimienta and Villanueva, Honduras, near San Pedro Sula, after flooding on the Rio Ulua from Hurricane Iota on November 18, 2020. Iota’s death toll has risen to 38 people, including 18 in Nicaragua and 14 in Honduras, but the full impact of the terrible hurricane will not be known for many days. (Image credit: Policia Nacional de Honduras)

Dare to hope: With the demise of catastrophic Hurricane Iota on Wednesday, the terrible 2020 Atlantic hurricane may have finally had its last deadly storm. The Atlantic hurricane season officially ends on November 30, but it is likely there will be no more deadly Atlantic storms in 2020. One or more weak named storms, perhaps staying out to sea, are still likely to form before the end of the year, but these are unlikely to cause mass destruction or loss of life.

Unfavorable conditions loom in tropical Atlantic

Sinking air over the tropics leads to drying, high pressure, and reduced odds of tropical storm formation – that’s exactly what is expected over the tropical Atlantic through early December given a state of the Madden-Julian Oscillation (MJO) unfavorable for Atlantic tropical cyclones.

The MJO is a pattern of increased thunderstorm activity near the equator that moves around the globe in 30 to 60 days; Odds of tropical cyclone formation increase when the MJO is strong and suitably located, but typically decrease for ocean basins not in the active portion of the MJO. During the formation of Hurricane Eta, the MJO was in a favorable place for enhancing Atlantic tropical cyclones, but it was transitioning to an unfavorable state when Hurricane Iota formed. It is expected to remain unfavorable into early December.

Favoring tropical cyclone formation in the coming weeks will be above-average ocean temperatures in the tropical Atlantic, plus an intensifying La Nina event in the eastern Pacific, which will contribute to below-average levels of wind shear over the tropical Atlantic. However, the current unfavorable state of the MJO, plus the near end of the climatological close of hurricane season, argue that the 2020 Atlantic hurricane season at last may have had its final deadly storm. That prediction is bolstered by the fact that over the past few days, multiple runs of the top three models for forecasting tropical cyclone genesis have not predicted formation of any new tropical storms through the end of November.

In a season with a proven track record for spitting out record numbers of named storms (30 so far), 2020 will still be able to produce one or more relatively inconsequential tropical or subtropical storms before the end of the year, perhaps resulting in a final nearly unfathomable tally of 31-33 named storms in this busiest-ever season on record.

The previous record-busy Atlantic hurricane season, 2005 with 28 named storms, had three named storms form after November 20: Tropical Storm Delta on November 22, Hurricane Epsilon on November 29, and Tropical Storm Zeta on December 30. None of those storms caused loss of life while they were named, although Delta killed seven people in the Canary Islands after it had transitioned to an extratropical storm. Only three deadly December tropical cyclones have been recorded in Atlantic history:

Tropical Storm Odette, Dec. 4-7, 2003, 8 killed in the Dominican Republic;
Hurricane Four, Dec. 1, 1925, 60 killed in Florida; and
Unnamed Hurricane, December 1779, 120 killed on ships in the Atlantic.

Figure 1
Figure 1. In this velocity potential (VP) anomaly plot from November 19, 2020, the MJO brings positive 200 mb VP anomalies (yellow colors) and reduced odds of tropical cyclone formation to the tropical Atlantic, with negative 200 mb VP anomalies (blue colors) over the Indian Ocean and Northwest Pacific. See further details* below. (Image credit: Michael Ventrice).
Figure 2
Figure 2. Predicted seven-day rainfall ending at 1 a.m. EST Thursday, November 26, from the 1 a.m. EST Thursday, November 19, run of the GFS model. The model predicted that rainfall amounts of more than five inches (orange colors) would affect portions of Central America. (Image credit: NOAA/AOML)

Two tropical disturbances to keep an eye on

An area of low pressure that formed on Wednesday over the southwestern Caribbean was bringing heavy rains to Panama and Costa Rica on Thursday. There is little model support for development of this disturbance, though it will likely bring 4-8 inches of rain to Panama and Costa Rica through Tuesday, as the system moves slowly west to west-southwest across Central America and into the Northeast Pacific. In a 1 p.m. EST Thursday tropical weather outlook, the National Hurricane Center gave 2-day and 5-days odds of development of near 0% to this disturbance.

How climate change is making hurricanes more dangerous

Also worth watching are the waters off the U.S. East Coast between the Bahamas and Bermuda, where models predict that an area of low pressure capable of becoming a subtropical storm may form by Monday as it moves rapidly to the northeast past Bermuda. In a 1 p.m. EST Thursday tropical weather outlook, NHC gave 2-day and 5-days odds of development of near 0% and 20%, respectively, to this disturbance.

The next name on the Atlantic list of storms is Kappa, the 10th letter in the Greek alphabet.

*Details on Figure 1: The amount of rising or sinking air can be inferred from the 200 mb velocity potential (VP) departure from average (also called the anomaly). Negative 200 mb VP anomalies mean that upper-level winds at the 200 mb level are diverging, causing rising air from below to replace the air diverging away at high altitudes. This rising air helps nurture thunderstorm updrafts, and favors low pressure and increased chances of tropical cyclone formation. Conversely, positive 200 mb VP anomalies imply converging air aloft, where sinking air, high pressure, and dry conditions will be unfavorable for tropical cyclone formation. In this plot, negative 200 mb VP anomalies (divergence) are cool-colored contours (the scale shows the departure from average in standard deviations); positive 200 mb VP anomalies (convergence) are warm-colored contours.

Editor’s note: Unless Tropical Storm Kappa forms, this “Eye on the Storm” blog and focus on Atlantic hurricanes soon will go into winter hibernation. Jeff Masters plans to post a wrap-up piece on the Atlantic hurricane season on November 30 or December 1, after which he and Bob Henson will continue writing often at this site on extreme weather and climate change and on other climate change issues as part of their ongoing “Eye on the Storm” features.


Website visitors can comment on “Eye on the Storm” posts (see below). Please read our Comments Policy prior to posting. (See all EOTS posts here. Sign up to receive notices of new postings here.)

Posted on November 19, 2020(3:53pm EST).

Topics: Weather Extremes
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HadesGodWyvern
HadesGodWyvern
10 hours ago

India Meteorological Department
Tropical Cyclone Outlook – 8:30 AM IST November 28 2020
==============================================

A low pressure area has formed over southern Andaman sea and adjoining areas of southeastern Bay of Bengal and Equatorial Indian ocean.

It is very likely to concentrate into a depression during next 48 hours and likely to intensify further thereafter. It is likely to move nearly westwards and reach southern Tamil Nadu coast around December 2nd.

HadesGodWyvern
HadesGodWyvern
10 hours ago
Reply to  HadesGodWyvern

The low pressure area (mentioned above) over Bay of Bengal after moving across Sri Lanka and extreme southern peninsular India is likely to emerge into southeastern Arabian sea around December 3rd.

NCHurricane2009
19 hours ago

Good evening to you all,

My latest birdseye view post and chart on the Atlantic tropics, highlighting the two AOIs that remain in the NHC tropical weather outlook, is at this link. In addition I discuss two more possible AOIs that could pop up unbelievably in early December. Looks like the 2020 Atlantic Hurricane Season does not care that the official end of the season is usually November 30.

Diablo Flaco
Diablo Flaco
5 hours ago

Sub-trop Kappa near Bermuda and Lambda near Costa Rica? After all these years, knowing the Greek Alphabet finally pays off.

NCHurricane2009
1 day ago

Good thanksgiving evening to you all, just posted my latest birdseye view chart and post of the Atlantic tropics after eating some turkey, viewable at this link.

This is my intro statement to that post, says how I feel about the latest round of activity (99L and AOI in the NE Atlantic) in the tropics: “Although today is the Thanksgiving holiday for many…the Atlantic tropics refuse to go on vacation.”

Diablo Flaco
Diablo Flaco
1 day ago

Could we get a sub-tropical Kappa near Bermuda this week?

NCHurricane2009
1 day ago
Reply to  Diablo Flaco

Should stay east of Bermuda thankfully.

Skyepony
1 day ago

comment image?w=600&h=408
99L

HadesGodWyvern
HadesGodWyvern
2 days ago

Tropical Cyclone Warning Center Perth
Tropical Cyclone Outlook – 2:00 PM WST November 26 2020
========================================

Tropical Low (01U) is currently located near 10.0S 91.0E, in the far northwest of the region. This low is forecast to move south through till Sunday before moving west and out of the region. There is a low risk of 01U intensifying into a tropical cyclone on Saturday and Sunday, prior to moving west of 90E and out of the region.

The low is not expected to have any direct impact on the Cocos Islands, however rainfall and thunderstorms are more likely while it lies in the northwest of the region, with this activity likely to be in a significantly easing or even clearing trend by Tuesday.

HadesGodWyvern
HadesGodWyvern
2 days ago

India Meteorological Department
Tropical Cyclone Advisory #24 – 8:30 AM IST November 26 2020
CYCLONIC STORM NIVAR (BOB04-2020)
==============================================

At 3:00 AM UTC, The cyclonic storm “NIVAR” moved northwestwards with a speed of 13 km/h during past six hours and lay centered over north coastal Tamil Nadu near 12.6N 79.4E, about 85 km north northwest of Puducherry and about 95 km west southwest of Chennai.

Cyclonic Storm “NIVAR‟ would continue to move northwestwards and weaken further into a deep depression during next 6 hours and into a depression by subsequent 6 hours.

3 minute sustained winds near the center is 40 knots with gusts of 50 knots. Estimated central pressure of the severe cyclonic storm is 994 hPa.

HadesGodWyvern
HadesGodWyvern
2 days ago

India Meteorological Department
Tropical Cyclone Advisory #23 – 5:30 AM IST November 26 2020
SEVERE CYCLONIC STORM NIVAR (BOB04-2020)
==============================================

At 0:00 AM UTC, The severe cyclonic storm “NIVAR” moved nearly northwestwards with a speed of 11 km/h during past six hours and lay centered over north coastal Tamil Nadu near 12.4N 79.6E, about 50 km north northwest of Puducherry.

“NIVAR” would continue to move northwestwards and weaken further into a cyclonic storm during next 3 hours.

Forecast and Intensity
=========================
12 HRS: 13.2N 78.8E – 30 knots (Deep Depression)
24 HRS: 14.0N 78.0E – Low Pressure Area

Storm Surge Warning
——————–
Tidal wave of about 0.5-1 m height above the astronomical tide is very likely to inundate the low lying areas of north coastal districts of Tamil Nadu (Villupuram and Chengalpattu districts) during next 03 hours.

As per satellite imagery, broken low and medium clouds with embedded intense to very intense convection lay over southwestern and adjoining west central Bay of Bengal, between 11.0N & 12.5N and 78.0E & 80.5E in association with the system. Minimum cloud top temperature is -93.0C.

3 minute sustained winds near the center is 50 knots with gusts of 60 knots. Estimated central pressure of the severe cyclonic storm is 982 hPa.