The Northern Hemisphere is currently facing an onslaught of typhoons and hurricanes, seemingly overnight. With 3 storms spinning in the North Atlantic - Hurricane Florence among them - the tropics have exploded to life at the annual season's peak.
Super Typhoon Mangkhut is the world's most intense tropical cyclone in the tropical Pacific, packing 170 miles an hour (273km per hour) winds.
Why the notable uptick in activity? In the Atlantic, in particular, it is all thanks to a sudden alignment of the two things which fuel hurricanes: wind and energy.
If the winds high in the atmosphere are very strong, they can shear apart a developing storm. It is ironic but true, as calm winds are required to create a hurricane. The total number of shear in the Atlantic has reached the annual minimum, kindling any fledgling storm and fostering its growth.
The Category 4 Hurricane Florence is headed directly for the Carolinas. As steering currents in the atmosphere are now slackening, concern is growing that Florence might stall - prolong its barrage and produce unbelievable amounts of rainfall.
Above: Wind speed and streamlines around the global tropics highlighting what are now six active tropical cyclones. Tropical Depression Paul was downgraded to a remnant low. (The Washington Post/earth.nullschool.net)
Florence also has company in the Atlantic. Helene is also a Category 1 west of Cabo Verde, boasting 90 miles an hour (144km per hour) winds. Although the storm is impressive on satellite, it will possibly remain over the open ocean. The storm is likely to become swept up in the jet stream over mid-September, 2018, probably dousing parts of Europe.
We're watching not one, but two additional systems in the Atlantic. A disturbance posted offshore of the Yucatan Peninsula will probably become a tropical depression by the weekend.
The National Weather Service might dispatch an Air Force reconnaissance airplane to probe the system on September 19th, 2018. The National Hurricane Center is advising locals along the coasts of Texas and Louisiana to monitor the system.
Another wave of low pressure several hundred miles southwest of the Azores might also develop tropical or subtropical features in the next couple of days, yet it's still no urgent threat to any land.
If the other 2 systems in the Atlantic develop into tropical storms, there could be 5 cyclones simultaneously. That has only ever happened once - between 10th and 12th September 1971.
Into the Pacific, Super Typhoon Mangkhut is creating winds sustaining speeds up to 170 miles an hour (274 ms per hour) and enormous waves as it treks about 200 miles (322 km) west of Guam.
Hawaii is now dealing with its own Pacific threat, as Tropical Storm Olivia is deluging the archipelago with up to 15 inches (38 cm) of rain in spots.
There's one additional system to watch west of Mexico, but it looks like it'll remain tame.
Therefore, combining all of this tropical storm action, how does it compare with what is normal?
The Accumulated Cyclone Energy (ACE) is a metric which combines the intensity and duration of storms. All across the Northern Hemisphere, the year is up at 159% of average for the date.
The greatest contribution to the anomaly comes from the East Pacific (245% of average), followed by the West Pacific (124% of average) - the Atlantic as well as Indian oceans are both a little above their climatological averages.
This increase of activity in the middle of September isn't a big surprise, though. Looking at the timeline of historical activity in every major basin, this time of year is no stranger to action:
-Storms in the West Pacific can occur any month but has a broad peak from July through October 2018.
-The East Pacific hurricane season is not so long (mid-May through the end of November) and has a broad peak during August as well as September.
-The Atlantic season is the shortest of them all (June through November), and it has a much more thin peak during the first half of September. Tropical storm activity is now typically elevated in all of these basins.
However, even at this active time, the current year is even busier than usual. Capital Weather Gang writer Phil Klotzbach, a hurricane researcher in the Colorado State University, has an online platform for tracking all of this activity.
Using all the data available thereat, when we can break things down by basin, we can see that all ocean basins are featuring near normal to above average tropical activity indexes for 2018:
-The Atlantic was indeed above average for the entire season up until August 21. Then things quickly slowed down, and it reached the average level of activity.
-The East and Central Pacific have been above average since June (except for a brief change below average towards the end of July).
-The West Pacific also has wavered around average through its season, but it's currently very high.
-The North Indian Ocean has certainly been above average since late May, though its usual amount of activity is quite low anyway.
What does that all mean regarding climate? The answer is not clear. There is also studies with data suggesting that the total number of storms that develop won't change significantly as a significant result of climate change.
Instead, there's a likelihood that those that develop could become increasingly strong. Still, one thing is clear: What is happening in the tropics worldwide at the moment is out of the ordinary.
References: The Washington Post, Science Alert
Your post is great and very interesting, thank you.
ReplyDeleteusps tracking map