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vox_mundi

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Hurricanes & Cyclones 2024
« on: January 09, 2024, 07:55:20 PM »
Hurricane Waves Hitting Americas Grow 20% per Decade: Study
https://phys.org/news/2024-01-hurricane-americas-decade.html



The U.S., Mexico and countries in the Caribbean are being battered by hurricane-induced ocean waves that have grown in areal size by 80% over the past 40 years, a new study has found.

The first global trend study of its kind, led by Hohai University in China, investigated the long-term changes in both the height and surface area coverage of global tropical cyclone ocean surface waves since 1979. Published in Nature Communications, the study found the coverage area of ocean waves generated by tropical cyclones increased by nearly 20% (167,000 km2, about the size of Florida State) per decade in the North Atlantic Ocean.

Globally, the area of ocean waves increased by 6% per decade from 1979 to 2022. The maximum height of ocean waves caused by tropical cyclones grew by 3% per decade.

"The rapid growth of tropical cyclone waves over recent decades is extremely worrying given their immense danger to communities, businesses and ecosystems. Our results show that the threat from their waves is escalating fast across the globe.

... Tropical cyclones, also known as hurricanes in the North Atlantic and East Pacific or known as typhoons in the West Pacific, are rapidly spinning storms that form over warm ocean waters in tropical regions. As tropical cyclones move across the ocean, their strong winds stir up large waves from the storm's center.

The highest tropical cyclone-induced ocean wave height ever recorded (defined as the mean height of the highest one-third of waves measured from trough to crest) was 24 m, caused by Typhoon Krosa in 2007 in the West Pacific.

In addition to wave heights and area coverage rising, the study also found that the total wave energy produced by tropical cyclones has increased by 9% per decade globally. The largest increase of 30% per decade was found in the East Pacific and North Atlantic.

... The researchers anticipate that ocean wave size (defined by the overall height and the footprint area) is likely to substantially increase in the future due to a combination of factors, including tropical cyclone intensity, size, and translation speed (how fast tropical cyclones move across the Earth's surface). The authors suggest more research is needed to understand the multiple effects of global warming on extreme wave height.

Jian Shi et al, Global increase in tropical cyclone ocean surface waves, Nature Communications (2024)
https://www.nature.com/articles/s41467-023-43532-4

-----------------------------------------------------------------

Observational Evidence of Overlooked Downwelling Induced by Tropical Cyclones In the Open Ocean
https://www.nature.com/articles/s41598-023-51016-0

Tropical cyclones (TCs) cause severe natural hazards and drive intense upper ocean cooling through a series of oceanic and atmospheric physical processes, including vertical mixing and upwelling. Among these processes, TC-induced warming of near-surface waters in the open ocean has rarely been noted. This study provides a detailed analysis of upper ocean responses to 30 TC events observed by two buoys in the western North Pacific between 2016 and 2021. Supplemented with numerical experiments, we suggest that downwelling frequently occurs at the periphery of upwelling regions (around the radius of the 34 knot wind speed) following the passage of a TC. Downwelling is identified via pronounced warm anomalies under a shallow mixed layer depth, and its dynamics are attributed to negative wind stress curl and current-induced convergence. These findings highlight the important role played by TC-induced downwelling and offer insights for reconsidering the influence of TCs on biogeochemical processes.

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morganism

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Re: Hurricanes & Cyclones 2024
« Reply #1 on: January 09, 2024, 08:24:42 PM »
Long termers are saying La Nina gonna be back by end of hurricane season 2024, and gonna have effect.

gerontocrat

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Re: Hurricanes & Cyclones 2024
« Reply #2 on: January 12, 2024, 06:09:14 PM »
Mauritius & Des Galets look like geeting a wallop Jan 15-16.

https://www.metoc.navy.mil/jtwc/products/sh0524prog.txt
FORECAST REASONING.

SIGNIFICANT FORECAST CHANGES: THIS INITIAL PROGNOSTIC REASONING
MESSAGE ESTABLISHES THE FORECAST PHILOSOPHY.

FORECAST DISCUSSION: TROPICAL CYCLONE (TC) 05S (FIVE) IS FORECAST
TO TRACK GENERALLY TOWARDS THE SOUTHWEST ALONG THE WEST SIDE OF THE
STEERING RIDGE FOR THE NEXT 36 HOURS. TRACK SPEEDS WILL REMAIN
RELATIVELY STEADY THROUGH THE FIRST DAY OR SO OF THE FORECAST AS
THE RIDGE REMAINS ENTRENCHED TO THE EAST. BY TAU 36, THE TRACK
BEGINS TO TURN MORE SOUTHWARD AND SLOWS DOWN AS THE RIDGE BEGINS TO
REORIENT TO A MORE NORTHWEST-SOUTHEAST AXIS. SHORTLY AFTER TAU 48,
TC 05S WILL BE FIRMLY SET UPON A SOUTHEASTWARD TRACK AS THE RIDGE
COMPLETES IS REORIENTATION PHASE, AND IS EXPECTED TO PASS BETWEEN
LA REUNION AND MAURITIUS AROUND TAU 96, THEN CONTINUE INTO THE OPEN
WATERS OF THE SOUTHERN INDIAN OCEAN. IN TERMS OF INTENSITY, THE
ENVIRONMENT IS OPTIMUM FOR RAPID INTENSIFICATION ONCE THE LLCC
FULLY CONSOLIDATES, WHICH IS EXPECTED IMMINENTLY. OPTIMUM
CONDITIONS ARE FORECAST TO CONTINUE FOR THE NEXT 48 HOURS, ALLOWING
THE SYSTEM TO INTENSIFY AT LEAST 60 KNOTS IN THE NEXT TWO DAYS.

CONDITIONS REMAIN FAVORABLE FOR ANOTHER 24 HOURS AFTER THAT, AND
ADDITIONAL INTENSIFICATION UP TO AT LEAST 105 KNOTS, AND POTENTIAL
HIGHER, IS EXPECTED PRIOR TO THE SYSTEM REACHING THE MASCARENE
ARCHIPELAGO. A RAPID DECREASE IN OCEAN HEAT CONTENT AND SSTS,
ACCOMPANIED BY A SHARP INCREASE IN SHEAR WILL INDUCE A SLOW BUT
STEADY WEAKENING TREND AFTER TAU 96 AS THE SYSTEM CONTINUES MOVING
POLEWARD.

MODEL DISCUSSION: DETERMINISTIC TRACK GUIDANCE IS IN GOOD OVERALL
AGREEMENT, WITH THE NOTABLE EXCEPTION OF NAVGEM, THROUGH THE FIRST
72 HOURS OF THE FORECAST. ALL OF THE GUIDANCE EXCEPT NAVGEM, WHICH
IS FAR TO THE EAST, IS CONFINED TO A 105NM ENVELOPE THROUGH TAU 72.
HOWEVER, THE NAVGEM IS PULLING THE CONSENSUS MEAN EASTWARD SUCH
THAT IT MARKS THE RIGHT SIDE OF THE MODEL ENVELOPE, WITH THE
REMAINDER OF THE CONSENSUS MEMBERS TO THE LEFT, OR WEST, OF THE
MEAN THROUGH TAU 72 WHILE THE ECMWF INTERMEDIATE FORECAST MARKS THE
WESTERN SIDE OF THE ENVELOPE, AND TRACKS THE SYSTEM OVER LA
REUNION. THE JTWC FORECAST LIES WEST OF THE CONSENSUS MEAN AND
CONSISTENT WITH THE GFS TRACKER THROUGH TAU 72 WITH MEDIUM
CONFIDENCE. AFTER TAU 72, THE GUIDANCE BEGINS TO SPREAD OUT,
PARTICULARLY IN THE ALONG-TRACK DIRECTION, WITH SPREAD INCREASING
TO AT LEAST 350NM BETWEEN THE ECMWF AND THE GALWEM TRACKERS. THE
JTWC FORECAST REMAINS JUST WEST AND SOUTH OF THE CONSENSUS MEAN
THROUGH TAU 120, WITH MEDIUM CONFIDENCE. INTENSITY GUIDANCE IS IN
GOOD AGREEMENT THAT THE SYSTEM WILL RAPIDLY INTENSIFY (RI), WITH
MULTIPLE RI AIDS TRIGGERING. ADDITIONALLY, THE COAMPS-TC ENSEMBLE
RI PROBABILITIES ARE SET AT 95 PERCENT THROUGH TAU 60, PROVIDING
HIGH CONFIDENCE TO THE FORECAST THROUGH TAU 48. ALL MEMBERS OF THE
CONSENSUS AGREE ON A LEVELING OFF OF THE INTENSITY AFTER TAU 72,
FOLLOWED BY A STEADY WEAKENING PHASE THROUGH THE END OF THE
FORECAST PERIOD. THE JTWC FORECAST TRACKS ABOVE MOST OF THE
GUIDANCE, CLOSE THE MOST AGGRESSIVE RI GUIDANCE, THROUGH TAU 48,
THEN CLOSELY TRACKS THE CONSENSUS MEAN THEREAFTER.

FORECAST CONFIDENCE:
   TRACK 0 - 72 HR: MEDIUM
   TRACK 72-120 HR: MEDIUM
   INTENSITY 0 - 72 HR: HIGH
   INTENSITY 72-120 HR: MEDIUM//
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MrGreeny

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Re: Hurricanes & Cyclones 2024
« Reply #3 on: January 15, 2024, 07:45:41 AM »
Hello everyone,

For those living in the Cairns area, I hope you are safe from Jasper, albeit being a weakened Category II system it packed a punch. Repair efforts are still underway.

Moving on...

According to computer models it seems a low is forming just off the upper Queensland coast, over the next couple of days this system will start moving away from the Australian coast and out into the Coral Sea, from there it is unknown whether or not this system will take a turn towards the coast or if it will remain offshore.

+240hrs synoptics predicts that the potential Tropical Cyclone will hit the coast, however models can be inaccurate and this is just an estimation, it is nowhere near accurate at this time and I will continue to monitor the situation over the next coming days.
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MrGreeny

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Re: Hurricanes & Cyclones 2024
« Reply #4 on: January 16, 2024, 06:54:00 AM »
POTENTIAL TROPICAL CYCLONE 05U -

While 05U is expected to move away from the Queensland coast, over the next several days we will begin to see it start turning back and potentially strengthen to "Severe" status by the middle of next week.

GFS models now show the potential Tropical Cyclone definitely hitting the coast, however it remains uncertain where the impact zone will be.

For now the potential impact areas are: Miriam Vale, Turkey Beach, Gladstone, Rockhampton and Yeppoon. Last models show the Tropical Cyclone taking a sharp curve turn towards Townsville and the surrounding areas, while this model was outdated it is still possible for it to take a turn and make a hit to those areas but that remains unknown.

Will keep monitoring this throughout the next few days.
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Rodius

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Re: Hurricanes & Cyclones 2024
« Reply #5 on: January 17, 2024, 01:32:49 AM »
POTENTIAL TROPICAL CYCLONE 05U -

While 05U is expected to move away from the Queensland coast, over the next several days we will begin to see it start turning back and potentially strengthen to "Severe" status by the middle of next week.

GFS models now show the potential Tropical Cyclone definitely hitting the coast, however it remains uncertain where the impact zone will be.

For now the potential impact areas are: Miriam Vale, Turkey Beach, Gladstone, Rockhampton and Yeppoon. Last models show the Tropical Cyclone taking a sharp curve turn towards Townsville and the surrounding areas, while this model was outdated it is still possible for it to take a turn and make a hit to those areas but that remains unknown.

Will keep monitoring this throughout the next few days.

There is a chance of two hurricanes in a row....

https://au.yahoo.com/news/threat-back-back-cyclones-hit-211600282.html

Surely this is El Nino at work

MrGreeny

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Re: Hurricanes & Cyclones 2024
« Reply #6 on: January 17, 2024, 08:43:15 AM »
POTENTIAL TROPICAL CYCLONE 05U -

While 05U is expected to move away from the Queensland coast, over the next several days we will begin to see it start turning back and potentially strengthen to "Severe" status by the middle of next week.

GFS models now show the potential Tropical Cyclone definitely hitting the coast, however it remains uncertain where the impact zone will be.

For now the potential impact areas are: Miriam Vale, Turkey Beach, Gladstone, Rockhampton and Yeppoon. Last models show the Tropical Cyclone taking a sharp curve turn towards Townsville and the surrounding areas, while this model was outdated it is still possible for it to take a turn and make a hit to those areas but that remains unknown.

Will keep monitoring this throughout the next few days.

There is a chance of two hurricanes in a row....

https://au.yahoo.com/news/threat-back-back-cyclones-hit-211600282.html

Surely this is El Nino at work

Usually not this active at this time of year but perfect temperatures and low wind shear makes this perfect for a powerful storm.

Some models predict moving away from the coast still... I think it's predicted to make landfall here in the next week or so.
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morganism

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Re: Hurricanes & Cyclones 2024
« Reply #7 on: January 23, 2024, 11:00:35 PM »
winter-prepares-to-take-a-break-so-well-talk-about-crawfish-recent-research-and-the-2024-atlantic-hurricane-season

(...)
Another interesting paper published in November in the European Geophysical Union’s Journal of Atmospheric Chemistry and Physics touches on how aerosols from anthropogenic (human) sources impact the destructiveness of hurricanes. What stood out about this article was their finding that an increasing concentration of aerosols near the immediate coast (say, as storms approach the petrochemical complexes of the Gulf Coast) can lead to a weaker but larger storm with an 11 to 22 percent increase in precipitation within 100km of the center. The study used Hurricane Katrina as a model storm, and they worked to utilize very sophisticated modeling to solve for this.

“For the first time, a 3-D atmosphere–ocean fully coupled regional model (WRF–ROMS) at the cloud-resolving scale was used to simulate Hurricane Katrina in order to investigate the aerosol–TC system with the inclusion of air–sea interaction,” the authors write.

What I think our readers should take away from this research is that it adds to the growing body of evidence that suggests hurricanes are becoming more moisture-laden as they approach land, which is resulting in more rain, more flooding, more damage, and more impacts to more people.
2024 hurricane season early vibes check

There have been some items published in recent weeks about the upcoming hurricane season. I’ve seen everything from people expecting an active season to a very active season to the “hurricane season from hell.” Hyperbole aside, what does the very early data actually show about the hurricane season that begins in just over 4 months?

The first question we’d ask is whether El Niño will continue into this summer. The answer to that question is still an uncertain one. Modeling is aggressively weakening the El Niño event by late spring, as is often typically the case with strong events like this one. The European model below, for example, has us close to “ENSO Neutral,” or “La Nada” by mid-summer, with extrapolation pushing us toward weak La Niña perhaps by the peak of hurricane season.
The ECMWF long range forecast suggests an aggressive weakening of El Niño this summer, but still some question as to whether or not we end up in La Niña. (ECMWF)

Why does this matter? La Niña events are much more favorable for active hurricane seasons than El Niño events. So if we were to hypothetically tip back into La Niña this summer, it would likely aid an active hurricane season.

Historically, since 1950 in hurricane seasons immediately following a higher-end El Niño, we average 6 hurricanes (with as many as 10 in 1998). A normal hurricane season has about 7 hurricanes, so one could argue that the season proceeding after stronger El Niños may not necessarily skew dramatically higher. From that end, I don’t know that we can currently read too much into El Niño vs. La Niña chances this summer and how they may influence the season.

That being said, one thing we can absolutely read into are sea-surface temperatures (SSTs). The globe’s oceans are undergoing a heat wave of sorts. In fact, water temperatures in the main development region of the Atlantic basin are currently in line with what you would normally expect to see in July. That’s not a typo.
(more)

https://theeyewall.com/winter-prepares-to-take-a-break-so-well-talk-about-crawfish-recent-research-and-the-2024-atlantic-hurricane-season/

vox_mundi

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Re: Hurricanes & Cyclones 2024
« Reply #8 on: February 06, 2024, 01:47:19 PM »
In a Warming World, Climate Scientists Consider Category 6 Hurricanes
https://phys.org/news/2024-02-world-climate-scientists-category-hurricanes.html

... Researchers investigated and detailed their extensive research in a new article published in the Proceedings of the National Academy of Sciences (PNAS), where they introduce a hypothetical Category 6 to the Saffir-Simpson Wind Scale, which would encompass storms with wind speeds greater than 192 mph.

When the team performed a historical data analysis of hurricanes from 1980 to 2021, they found five storms that would have been classified as Category 6, and all of them occurred in the last nine years of record. They determined a hypothetical upper bound for Category 5 hurricanes by looking at the expanding range of wind speeds between the lower-category storms.

... Their models showed that with 2 degrees Celsius of global warming above pre-industrial levels, the risk of Category 6 storms increases by up to 50% near the Philippines and doubles in the Gulf of Mexico and that the highest risk of these storms is in Southeast Asia, the Philippines, and the Gulf of Mexico....

Wehner, Michael F. et al, The growing inadequacy of an open-ended Saffir–Simpson hurricane wind scale in a warming world, Proceedings of the National Academy of Sciences (2024)
https://www.pnas.org/doi/10.1073/pnas.2308901121
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Richard Rathbone

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Re: Hurricanes & Cyclones 2024
« Reply #9 on: February 06, 2024, 02:09:15 PM »

vox_mundi

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Re: Hurricanes & Cyclones 2024
« Reply #10 on: February 08, 2024, 11:27:55 PM »
Tropical Cyclone Genesis Projected to Move Toward the Poles
https://phys.org/news/2024-02-tropical-cyclone-genesis-poles.html


The zonal-mean distribution of the difference in panels (a–c) 850-hPa relative vorticity (10−6 s−1) and (d–f) 200-hPa divergence (10−6 s−1) during JASO in the Northern Hemisphere and JFMA in the Southern Hemisphere (the scale on the left). The difference is taken between (a, d) HST and NWA, (b, e) W2K and HST, and (c, f) W4K and HST. The solid line indicates the climatology of the zonal-mean (a–c) 850-hPa relative vorticity and (d–f) 200-hPa divergence in HST (the scale on the right). Credit: Geophysical Research Letters (2024). DOI: 10.1029/2023GL107189

In a recent study published in Geophysical Research Letters, researchers unveil a poleward shift of tropical cyclone (TC) genesis on a global scale as a result of climate change. Led by Dr. Xi Cao from the Institute of Atmospheric Physics, the research team collaborated with experts from institutions including the University of Tokyo, Zhejiang University, Yunnan University, the National Climate Center, and the University of New South Wales.

The impact of climate change on TC activity has been a subject of widespread concern due to the potential for disasters such as gales, heavy rain, and storm surges, leading to economic losses and casualties in coastal regions worldwide. However, the lack of consensus on changes in the frequency and location of TC genesis under global warming has created uncertainty in assessing the comprehensive impact of climate change on TC activities.

While climate models have previously projected a decrease in TC genesis frequency in future warming, the global nature of the latitudinal change in TC genesis has remained uncertain.

The research team utilized d4PDF simulations, known as the database for policy decision-making for future climate changes, to reveal a robust poleward shift of TC genesis during active seasons in both hemispheres, with the rate of TC genesis decreasing within latitudes equatorward of 15° and increasing poleward of 15° in each basin.

The projected shift is attributed to the weakening of the Hadley circulation, driven by increased upper tropospheric warming. The study estimates that the signal of TC genesis is expected to emerge over high latitudes of the Arabian Sea, South Atlantic, and South Pacific Oceans at 2 K warming, with implications for assessing the reliability of future TC-related changes in climate models and estimating increased TC-related hazards at higher latitudes under global warming.

"Our research underscores the dynamic nature of tropical cyclone genesis, revealing a significant shift towards the poles." Dr. Cao, the first and corresponding author, explains the teams' finding, "This emphasizes the critical connection between climate change and the evolving patterns of these weather phenomena."

Xi Cao et al, The Projected Poleward Shift of Tropical Cyclogenesis at a Global Scale Under Climate Change in MRI‐AGCM3.2H, Geophysical Research Letters (2024)
https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2023GL107189

Abstract

Future climate projections suggest a poleward shift of the maximum intensity of tropical cyclones (TCs) over the western North Pacific. However, the global nature of the latitudinal change in TC genesis under global warming remains poorly understood. We show, using large-ensemble high-resolution atmospheric model simulations (d4PDF) with four warming scenarios, that the poleward shift is a robust change over the globe, attributable to the weakening of the Hadley circulation. The weakened ascent driven by the upper-tropospheric warming suppresses the TC genesis within 5°–20° latitudes, whereas the weakened descent enhances the TC genesis in the poleward latitudes. We further estimate the poleward shift of TC genesis to emerge at the 2 K global warming over the Arabian Sea, South Atlantic and Pacific Oceans and at the 4 K warming over the North Pacific. The present results underscore the potential for increasing social and economic risks associated with TCs at higher latitudes.


Key Points
  • We project a global feature of the robust poleward shift of tropical cyclone (TC) genesis during active seasons of both hemispheres
  • More TC genesis at high latitudes can be attributed to the weakening of the Hadley circulation
  • Poleward shift of TC genesis emerges at 2 K warming over Arabian Sea, South Atlantic and Pacific Oceans and at 4 K warming over North Pacific
Plain Language Summary

Climate models have projected a decrease in TC genesis frequency in future warming. However, the global nature of the latitudinal change in TC genesis under global warming remains uncertain partly due to insufficient resolution as well as the ensemble size of climate model simulations. We show a global feature of the robust poleward shift of the TC genesis during the active seasons of both hemispheres scaled with the global warming level, which can be attributed to the weakening of the Hadley circulation. The weakened ascending branch of the Hadley circulation, driven by the increased upper tropospheric warming, potentially hinders TC genesis within 5°–20° latitudes. Conversely, the weakened descending branch of the Hadley circulation enhances the likelihood of TC genesis within 20°–35° latitudes. We further estimate that the signal of TC genesis is expected to emerge over high latitudes of the Arabian Sea, South Atlantic and South Pacific Oceans at the 2 K warming and at the 4 K warming over the North Pacific. The present analyses have significant implications not only for assessing the reliability of future TC-related changes in climate models but also for estimating the increased TC-related hazards at higher latitudes under global warming.
“There are three classes of people: those who see. Those who see when they are shown. Those who do not see.” ― anonymous

Insensible before the wave so soon released by callous fate. Affected most, they understand the least, and understanding, when it comes, invariably arrives too late

CalamityCountdown

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Re: Hurricanes & Cyclones 2024
« Reply #11 on: February 17, 2024, 07:42:49 PM »
According to https://tropical.atmos.colostate.edu/Realtime/index.php?arch&loc=northatlantic, the accumulated cyclone energy of North Atlantic hurricanes has been above 95 for each of the past 8 years (2016  thru 2023) and above 100 for 7 of the last 8 (2022 was the outlier with 95). Comparing this result to the previous 30 years, 14 out of the previous 30 years had accumulated energy below 95 (47%). I doubt many readers of this forum will be surprised by the fact that years with accumulated cyclone energy of North Atlantic hurricanes with high intensities are increasing.

I conducted this review because I speculated it highly likely that given the warmer ocean temperatures, that the Carribean Islands, North Atlantic and Gulf of Mexco coastal communities are likely to be devastated by the next round of hurricanes following the flip of ENSO to La Nina.

However, when comparing accumulated energy years to El Nino and La Nina years, I found that while there is definitely a correlation, it is not as strong as I had expected to find https://ggweather.com/enso/oni.htm. While El Niño generally tends to suppress Atlantic hurricane activity, and La Niña tends to enhance it, an eyeball review of the results suggests that it does not appear to be highly predictive of whether there will be destructive hurricane activity during 2024. Thus, if there is a flip of the ENSO cycle from El Niño to La Niña, as some forecasters are predicting, it makes a devastating hurricane season more likely, but not a certainty.

While coastal communities may not be as vulnerable to hurricanes in 2024 as I had supposed before starting this review, I fear that the warmer ocean temperatures will lead to more devasting Atlantic hurricanes in the not too distant future during both El Niño and La Niña years.
« Last Edit: February 17, 2024, 08:06:03 PM by CalamityCountdown »

Richard Rathbone

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Re: Hurricanes & Cyclones 2024
« Reply #12 on: February 19, 2024, 06:36:00 PM »
https://yaleclimateconnections.org/2024/02/a-rare-bird-in-the-south-atlantic-tropical-storm-akara/

Quote
The only ocean basin on Earth that does not regularly see tropical cyclones develop is the South Atlantic, but it had a rare tropical storm form on Sunday night. Tropical Depression 01Q was designated by the Brazilian Navy Hydrographic Center at 7 a.m. EST Sunday and by 7 p.m., it had been upgraded to Tropical Storm Akará, with top sustained winds estimated at 40 mph and a central pressure of 1,000 millibars.

Quote
On those few occasions when tropical cyclones do form in the South Atlantic, they are typically located within a few hundred miles of the coast of Brazil. Such was the case with Akará, which was centered about 300 miles southeast of São Paolo as of 7 p.m. EST Sunday.

Quote
Until the 2000s, it was widely thought that full-fledged tropical cyclones did not form in the South Atlantic. Although waters can be sufficiently warm, there is often too much wind shear, and tropical waves that can serve as seedlings for tropical cyclones do not stream regularly off the coast of southern Africa as they do from northern Africa. For these reasons, the South Atlantic was not canvassed by reconnaissance flights, and satellite imagery was not monitored closely for tropical development.

Quote
In 2004, expectations were upended when a nontropical system off the coast of Brazil gradually transitioned into a tropical cyclone and then turned back westward. The system came to be known as Hurricane Catarina, as it made landfall in the Santa Catarina province of Brazil as a Category 1 equivalent on March 27, 2004. More than 38,000 structures were damaged, and another 1,468 collapsed, with three people killed and 185 others injured.

After Catarina, forecasters and researchers began to pay closer attention to the South Atlantic, reviewing older satellite images and other evidence of past activity. Research released in 2012 found that 63 subtropical cyclones had formed between 1957 and 2012, or about one subtropical cyclone every year. In the eight years from 2015 through 2023, there were 13 more subtropical storms, as well as Tropical Storm Iba in 2019 and short-lived Tropical Storm 01Q in 2021 (which was recognized by NOAA but not named by the Brazilian Navy).