The Atlantic Hurricane season 2020 stays on the course to becoming the most active on record. The environmental conditions over the Caribbean will lead to a new Tropical storm formation in the coming days, it will Eta. The 7th storm name from the Greek Alphabet list, past the previous record set in 2005. Model guidance hint the new tropical system could turn towards the United States, again!
There have been so many records set in this beyond exceptional 2020 Atlantic Hurricane season, it is almost too hard to follow up. But we have it under control, and it has been an outstanding season.
2020 Hurricane season is now going deeper into the Greek alphabets and history books.
The last active storm was Hurricane Zeta earlier this week. Zeta had two landfalls, the first one in the Yucatan peninsula on Oct 27th and another, more intense one, just 36 hours later in Louisiana (Oct 28th). Explosive intensification occurred in the final 12 hours prior to the landfall south of New Orleans.
The first Hurricane Zeta’s landfall was in the Mexican state of Quintana Roo as a Category 1 hurricane. It set a new record as it was the 3rd named storm to make landfall in Quintana Roo this month (Gamma and Delta were the other two). The previous record for October Quintana Roo named storm landfalls was two, set in 1887 and 2005.
Hurricane Zeta had an increase in the peak winds by 45 mph in its 26 hours prior to landfall – the most on record in the Gulf of Mexico so late in the calendar year. Zeta’s landfall was the 3rd landfall in Louisiana and the fifth (5th) landfalling storm this season, passing the previous calendar year record of four (4) in 2005.
Hurricane Zeta was also the 11th landfall in the United States mainland this season, a new record since 1916. The previous record was 9 landfalls in one season.
With the maximum sustained winds of 110 mph, it is the strongest hurricane to make landfall in the United States this late in the calendar year since the Halloween Hurricane of 1899, according to the dr. Phil Klotzbach’s report on Twitter.
After landfall, Zeta rapidly weakened and literally raced across the eastern part of the United States. Reaching the East Coast by Friday afternoon (just 36 hours later). It traveled more than 1200 miles in a period of 24 hours and begin re-developing into an extratropical storm in the warm Atlantic waters east of Cape Cod.
And now, it seems that there is much more coming up… Tropical Storm Eta is in sight!
During the late season (October and November), a tropical activity gradually shifts into the Caribbean region, which has been experiencing much above normal sea temperatures this year. Extremely warm sea temperatures are also spread deeper into the ocean waters.
Conditions remain supportive for more activity
A deep MJO wave is underway over the Caribbean region and the Tropical Atlantic, leading to increasing thunderstorm activity and favorable for the formation of new tropical systems.
Another deep tropical wave has crossed the Leeward Islands into the Caribbean region and is now emerging west, likely to organize into a tropical storm sometime next week.
The official hurricane season for the Atlantic Basin (the Atlantic Ocean, the Caribbean Sea, and the Gulf of Mexico) is from June 1st to November 30th. The peak of the season is from mid-August to late October.
By the end of October, the 2020 hurricane season still has about a full month until we close the books at the end of the season.
At the beginning of the hurricane season, NOAA, TWC, and NCSU forecasters predicted: “There will be 13 to 22 named tropical storms in 2020, where 6-9 of those would reach hurricane strength, and 3-4 of them attaining major strength.” The official name list had 23 names reserved this year.
As of Sept 18th, the official list usage has been completed as all the reserved names were already used by that date. Since then, the Greek alphabet list is in use.
The next system from the list is Tropical storm Eta, it will be the 28th named storm of the 2020 Atlantic Hurricane season.
Then, the 2020 season will be aligned with the 2005 season. The only other year that the Greek alphabet was in use.
STORM NAMES ENTERING THE UNCHARTED GREEK ALPHABETS
When Tropical Storm Eta forms, it will use the seventh (7th) letter of the Greek alphabet that was last used in 2005. This means that it will be beyond the existing record of 6 names from this list.
Any additional storm names will therefore go into uncharted territory, so we will be dealing with unprecedented records.
The environmental conditions across the Caribbean Sea are very conducive for further development, as a strong and deep MJO wave is now supporting upper-level divergence over the region.
The 2020 Atlantic Hurricane Season ends at the end of November, while the most active years have seen storms forming also in the off-season in December before.
The 2020 hurricane season is now very likely on the way for a new record for the most named storms in one season. Past 28 named storms from 2005 – the only year using the Greek alphabet until now.
2005 Atlantic hurricane season churned out powerful hurricanes like Katrina, Rita, and Wilma.
And although the intensity of the 2020 hurricane season might not be as strong as the 2005 season, we are still facing the fact, that this year could generate even more than 30 named storms in total for the season.
HOW IS THE HURRICANE SEASON SO FAR?
The Atlantic hurricane season remains on course for a record-setting year to date, Oct 31st. There were 27 named storms, which is about 250 % of the long-term average (11.0) for this time period. So far, there were almost double the number of hurricanes (11) and four major hurricanes (Laura, Teddy, Delta, and Zeta).
25 storms out of those 27 total, had the earliest formation date on record.
Major hurricanes Laura, Teddy, and Delta have all peaked at Category 4 strength. Laura and Delta both made destructive landfalls in Louisiana. Delta’s center came ashore on October 9th and, interestingly, the landfall was just about 15 miles east of the landfall point of Hurricane Laura, which struck at the end of August.
The state of Louisiana, or better said its southern parts along the central Gulf Coast of the United States, were a hot spot so far this year. There have been 5 storms that made landfall in Louisiana. 3 of those five were hurricane landfalls (Laura, Delta, and Zeta).
Laura made landfall as a Category 4, while Delta and Zeta were a Category 2 when they came ashore in Louisiana. Laura and Delta affected the same areas with severe wind and storm surge damage. Zeta made landfall further east, due south of New Orleans.
The Atlantic, Caribbean region, the Gulf of Mexico, and the East Coast of the United States were also the most active tropical regions globally this year.
There have been almost 98 named storm days so far, which is around 183 % of the average number (53.4). As we can see from the graphics below (see the right column), all the forecast parameters are above average. Including hurricane days, major hurricanes, and major hurricane days. Provided graphics are by Dr. Philip Klotzbach.
Accumulated Cyclone Energy (ACE index)
The Accumulated Cyclone Energy is the energy output of a hurricane season, calculated as an index (ACE index). It is a metric used to express the energy used by a tropical cyclone during its lifetime.
The index calculation takes the cyclone’s maximum sustained winds every six hours and multiplies it by itself to generate the values. The total sum of these values is calculated to get the total for a storm.
The current Atlantic basin ACE is, as of October 30th, held at 143.8. That is an impressive 47 percent higher than during a normal season to this date (98.1).
The highest ACE so far this season was generated by Teddy (27.8), Paulette (15.9), Delta (15.7), Epsilon (13.1), and Laura (12.8). The last system – hurricane Zeta – added another 7.5 to the ACE index total for the Atlantic 2020 hurricane season.
Record-breaking 11 landfalls in the Continental United States
But there is more. The 2020 Atlantic hurricane season has had a record-breaking 11 landfalls of tropical storms (or hurricanes) in the United States mainland this season.
Hurricane Delta and Zeta have helped the season to break the previous record of nine landfalling systems more than 100 years ago – in 1916.
Hurricane Delta was the first hurricane named after a Greek alphabet letter use which made landfall on the United States mainland. These are 11 named storms that made landfall in the continental United States this year (2020): Bertha, Cristobal, Fay, Hanna, Isaias, Laura, Marco, Sally, Beta, Delta, and Zeta.
And to make it even greater, there were six (6) hurricane landfall out of those 11 named storms landfall in the United States mainland. This ties with the 6 hurricane landfalls in one full season (1985 and 1886).
The 2020 hurricane season has also tied another record – there were 3 tropical storm formations in a single day. Tropical Storm Wilfred, Subtropical Storm Alpha, and Tropical Storm Beta formed on Sept 18th. This has happened only once before, in 1933.
The graphics above show all the tropical storm tracks for the 2020 Atlantic Hurricane season so far. The image is provided by Wikipedia, based on the official data from the National Hurricane Center (NHC).
A DEEP MJO WAVE IS UNDERWAY
So, what can we expect for the rest of the Atlantic 2020 hurricane season and the month of November? The sea surface temperatures remain very warm in the Western Atlantic, and extremely warm over the Caribbean region.
There, the sea surface temperatures are reaching close to 30 °C (86 °F). Especially across the northwestern Caribbean Sea, around Cuba and Jamaica.
This is definitely a worrying sign as sea waters remain much higher than the long-term average. So the upcoming tropical systems will have the most important ingredient ready, therefore strongly supporting the rapid or even explosive development of thunderstorms.
Actually, the majority of the North Atlantic, tropical Atlantic, and the Caribbean are well-above average. Also the Eastern Pacific. About 1-2 °C warmer, even more across the Northwest Atlantic.
Waters remain warm, much above the long-term average across the whole Gulf of Mexico, around Florida, the Bahamas, and along the East Coast of the United States. Definitely an important ingredient for the upcoming weeks of tropical activity.
Notice also a rapidly cooling water of the Eastern and Central Pacific – a strong Lá Nina is developing.
WHAT IS A MADDEN-JULIAN OSCILLATION?
The Madden-Julian Oscillation (MJO) is the largest and most dominant source of short-term tropical variability, it is an eastward-moving wave of thunderstorms, clouds, rain, winds, and pressure. It circles the entire planet on the equator in about 30 to 60 days.
Through the second half of October, a new wave re-emerged from the eastern Pacific into the Caribbean region and Tropical Atlantic. It is forecast to persist over the region and expect into early November as well.
The MJO consists of two parts: one is the enhanced rainfall (wet) phase and the other is the suppressed rainfall (dry) phase. This means there are increased storms and rainfall on one side and reduced storms and drier weather on the other side.
The air parcels are diverging (moving away) over the wet phase, and converging (moving together) over the dry phase. This horizontal movement of air is referred to as the Velocity Potential (VP) in the tropics.
We are able to track the entire MJO wave movement by looking at the larger scale air parcels movement. With the weather model data, we can easily see the areas where the air is rising and where it is subsiding.
Another important factor is the Ocean Heat Content (OHC). OHC takes into account the depth of the sea, and how warm the water layers are deep below the sea surface. In this month, we can still see a large pool of high available heat energy with a very warm water layer running down quite deep.
Deepwater being so warm as this season, provides a very favorable environment of a thick layer of warm water. Tropical systems are fueled by these warm layers, as deep convective storms draw energy from hot water.
Long story short: the thicker the warm layers are, the more fuel/energy is available to feed the storms.
It is a very obvious feature on the week 1 forecast (the first week of November), that the MJO wave will remain very deep and strong. Such a MJO phase is normally lowering the pressure and providing a strong boost to thunderstorm activity.
The above graphics, provided by Michael J. Ventrice, Ph.D. represent an MJO wave with filtered VP200* anomalies for the current state, for the week 1 forecast, and for the week 2 forecast. Cold colors are representative of a more favorable state over the Atlantic for tropical cyclogenesis while warm colors represent a less favorable state for tropical cyclogenesis.
*VP200 – means a Velocity Potential (VP). It is an indicator of the large scale divergent flow, so at upper levels in the tropics. The negative VP anomalies (shaded blue in the diagram) are closely tied to the divergent outflow from enhanced convective regions.
Below is the video animation forecast of atmospheric rivers from the Western Atlantic into the Caribbean region. The atmospheric rivers (moisture) lead to the formation of a tropical storm. This will be Storm Eta. This video is a great display of just how fluid in the atmosphere really works.
HISTORY OF OCTOBER/NOVEMBER HURRICANES
With above normal October tropical activity, we are now looking at what could November 2020 brings us with this above-normal Atlantic Hurricane season.
Typically in October and November, more westerly prevailing winds develop across the central and eastern United States. This tends to keep any potential tropical systems away from the western parts of the Gulf of Mexico.
But such steering winds and circulations more likely lead to the formation of the tropical systems over the Caribbean, moving towards the Bahamas and Florida, and further along the East Coast of the United States.
The below map, based on the NHC past data, is showing where Atlantic named storms have formed through the month of October (between 1851 and 2019). It is an obvious sign that all the major hurricanes (Category 3 or greater) have formed in the central or western Caribbean Sea region.
In 2020, the Western Caribbean region surely greatly fits into these statistics, as Gamma (tropical storm), Delta, Epsilon, and Zeta (all hurricanes) originated in the Caribbean.
Based on statistics through the years, a typical hurricane season sees the month of November with more quiet month than October. As we can see on the storm frequency graph below from NOAA, November still brings some activity and even destructive hurricanes. The chart is the data averaged through 100+ years, so obviously not every year follows the same pattern.
Late October has a history of some powerful hurricanes, originating from the Caribbean region and moving towards the United States, e.g. Sandy (2012), Wilma (2005), or Mitch (1998).
And also the Hurricane Michael made a destructive landfall as a Category 5 hurricane in Florida Panhandle on October 10th, 2018. Michael was the first Category 5 hurricane to strike the United States mainland since Andrew back in 1992.
And indeed Hurricane Delta and Zeta from the Atlantic hurricane season 2020.
What about November?
Here is the statistic chart for all the November 1-10th tropical storms formation in the Western Atlantic and the Eastern Pacific. 45 storms formed in this period over the last 164 years. Data are provided by NOAA.
November also has some history of destructive hurricanes, e.g. Paloma (2008), Ida (2009), Otto (2016), and Hurricane Mitch (1998) – it did form in October but dissipated on Nov 9th.
Then there was Hurricane Kate (1985) that hit Florida and Hurricane Lenny (1999) which still holds the record as the strongest November hurricane. Lenny had peak sustained winds of 155 mph while grazed over Puerto Rico.
The average trajectory of the tropical systems tracks in October and early November is towards the north and northeast. This puts Cuba, Florida, and the Bahamas at risk of landfall if storms organize over the Caribbean region.
Actually, the month of October is the statistical peak of tropical storm landfalls in Florida. So even early November statistics are not far behind.
So, a typical October/November bring storm tracks closer to land, from the western Caribbean Sea to the eastern Gulf of Mexico, Florida, and also affect the East Coast of the United States.
WHAT’S NEXT IN THE TROPICAL ATLANTIC?
After Hurricane Zeta landfall in Louisiana this week, the next sight is the westward-moving tropical wave in the Eastern Caribbean Sea.
A broad area of low pressure located over the Eastern Caribbean, to the west of the Windward Islands. It continues to produce a large area of organized and explosive thunderstorms.
According to the National Hurricane Center (NHC), tropical storm development is very likely in the coming days. Both the oceanic and environment are surely prime for additional tropical storm formation. Atlantic hurricane season continues and on the way for new records to break.
Regardless of development, this disturbance is expected to produce heavy rainfall and flooding threat across portions of Jamaica and southern Hispaniola through the weekend into the early days of next week.
ANOTHER TROPICAL WAVE IN THE CARIBBEAN
A vigorous tropical wave is located over the central Caribbean Sea and continues to produce a concentrated area of strong thunderstorms. This system is gradually becoming better organized, and both oceanic and environmental conditions are conducive for further development.
A tropical depression is expected to form during the next day or so while the disturbance moves generally westward into the western Caribbean Sea. Global models are hinting it will then become a Tropical Storm Eta over the next five (5) days.
Interests in Jamaica, Honduras, Guatemala, and Nicaragua should monitor the progress of this system. The European model, ECMWF, is simulating a tremendous amount of rainfall over the next 10 days. Even more than 30 inches (750 mm) in total in parts of Honduras.
A lot of rainfall is also forecasted across Guatemala and Jamaica, 20-25 inches (500-600 mm) until November 10th. Attached is the map of total rainfall, provided by Windy.com.
The National Hurricane Center (NHC) is giving the system a 100 percent (%) chance to become a tropical depression this weekend and 100 % change it to become Tropical Storm early next week.
The next tropical system from the Greek Alphabet list will be a Tropical Storm Eta.
ETA COULD TURN TOWARDS THE UNITED STATES
The Western Caribbean region is closely monitored as the weather models continue to forecast another potentially dangerous tropical storm (or even a hurricane) to form in the coming days.
Model guidance is raising concerns that a broad area of low pressure – called a Central American Gyre* – near Central America will begin developing.
This will likely churn out the Storm Eta, as the global models are currently trending is the development of a strong tropical storm over the western Caribbean over the next few days. The majority of the models push the system west-northwest across the region. The map is provided by Windy.com.
While the intensity forecast suggests even a hurricane strength will be possible later, sometime around mid next week.
Both global weather models, ECMWF and GFS, then hint at an increased potential of turning the wave north-northeast with the potential track towards Cuba, potentially even then eastern portions of the Gulf, Florida, or the Bahamas late next week.
With the extremely favorable oceanic waters and high mid-level moisture, the low-shear environmental support, and deep MJO wave underway from the west, development is quite supportive and odds are high.
However, if a more northerly trajectory takes place, that would definitely enhance the concern the system could become a threat for the eastern Gulf Coast and the United States mainland at some point. That could potentially bring an unprecedented 12th landfall this season.
*Central American Gyre (CAG)
The broad low-pressure area over the Western Caribbean is officially called a ‘Central American Gyre‘, or shortly CAG). The attached graphics below indicate such a Central American Gyre these days, while the sea waters of the Caribbean are extremely warm.
Central American gyres (CAGs) are broad lower-tropospheric cyclonic circulations occurring near Central America, in other words, a cyclonic gyre. They often form in response to the convectively active phase of the MJO (Madden-Julian Oscillation) over Central America.
On the intraseasonal scale, an active MJO wave can enhance westerly zonal winds in the eastern Pacific and promote convection over Central America, both then features that lead to a formation of the Central American Gyre development. CAG can yield exceptional rainfall amounts, leading to catastrophic flooding and large societal impacts in Central America.
There are several cases where these gyres lead to a tropical formation, for example, Tropical Storms Frances in 1998 and Nicole in 2010. And indeed Hurricanes Delta and Zeta this year.
SEASON ON THE COURSE TO MORE THAN 30 NAMED STORMS
The last active storm was Hurricane Zeta, the 27th named storm of the 2020 Atlantic hurricane season.
Atlantic hurricane season 2020 now continues into uncharted territory, past the previous record of 6 Greek alphabets used in 2005. And obviously 2020, as hurricane Zeta was the 6th letter used. Tropical Storm Zeta was the last storm name that was designated by the National Hurricane Center in 2005, the only year using the Greek alphabet prior to the 2020 hurricane season.
The next named system will be Tropical Storm Eta, the 28th of the 2020 Atlantic Hurricane season. When Storm Eta forms, it will use the seventh (7th) letter of the Greek alphabet that was last used in 2005. So past the existing record of 6 names from this list.
Nevertheless, based on the current statistics, the Atlantic hurricane season 2020 is only one system away from the record of 28 named storms in 2005.
For example, the 2005 season had eight (8) additional storms forming in October itself and three storms more forming in November. While 2020 hurricane season had ‘only’ four (4) storms forming in the month of October. Those were Gamma, Delta, Epsilon, and Zeta.
With potentially a few more storms forming through November, we are definitely aiming towards Nu or Xi storm names. That is halfway through the Greek Alphabet names.
There seems to be a fairly high probability that the well-above-average western Atlantic and Caribbean region sea temperatures would be favorable for tropical storm formation even in December this year.
Nevertheless, there is still a long way to go before we will be closing the books of this historic 2020 Atlantic hurricane season.
We will be covering the tropical activity further, providing regular updates on the ongoing activity. The next update is scheduled when the tropical-storm-force strength of the upcoming Storm Eta appears. Stay tuned!
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