Changes in Tropical Cyclone Intensity & Track

[Mike OReilly]

Thanks for posting this Gord. Makes sense to extend the scale, given the growing number of high-intensity storm.

[Don C L]

I know this thread is concerned with cyclones but here on the US west coast we just had hurricane force winds, just offshore, from an unusually deep low that came down from the north Pacific (and in turn sucked up a plume of tropical moisture.) I wonder if there is data on just the frequency and distribution of deeper lows aside from those associated with warm water-fed cyclones/hurricanes/typhoons?

[MicHughV]

I think what often gets forgotten is that force of the wind goes up as the square of wind speed.
ie, a small increase in wind speed can make a considerable difference on the force exerted on any object.

[GordMay]

Climate change impacts the development of bomb cyclones, and other severe storms, in a number of very direct ways.

A bomb cyclone is a large, intense storm, that's associated with a sudden significant drop in atmospheric pressure [specifically, one millibar or more per hour, over a 24-hour period], that meets a mass of high-pressure air.

Bomb cyclones form in areas, outside of the tropics, driven by air masses, of different temperatures, colliding, and jet stream disturbances.
Hurricanes, on the other hand, form at low latitudes, in the tropics, and are driven by the heat content, of the lower atmosphere and ocean.

The extra warming in the oceans is increasing that contrast between that very cold arctic air coming down, and the warm, moist air, that’s feeding the air mass, to the east of that arctic air.

Additionally, warming of the air and oceans leads to an increase in evaporation, meaning there is more water vapour in the atmosphere.
That water vapor condenses into clouds, releases heat, and adds energy to storms, similar to what happens with a hurricane. It also provides more moisture to fuel the storm.

I believe we’re seeing a major uptick in the frequency of heavy precipitation events, and this is certainly connected to this increase in water vapour, that’s in the atmosphere, as a result of the warming oceans and air.

[GordMay]

Originally Posted by GordMay

Climate change impacts the development of bomb cyclones, and other severe storms, in a number of very direct ways ...
... I believe we’re seeing a major uptick in the frequency of heavy precipitation events, and this is certainly connected to this increase in water vapour, that’s in the atmosphere, as a result of the warming oceans and air.

Atmospheric rivers are expected to increase in intensity in California due to climate change.
Atmospheric rivers are essentially narrow currents in the air, that carry lots of water vapor, across the world. They transport most of that water vapor outside of the tropics, then release it, in the form of either rain or snow.

Human-caused climate change is increasing the intensity of many extreme weather events, and atmospheric rivers are no exception, at least in California.
Research by USGS scientists has found that over the past 70 years, there is a pattern of increasing water vapor transport onto the West Coast, associated with ocean surface warming. Atmospheric rivers aren’t predicted to become more frequent, but California’s precipitation will become more volatile, with more water concentrated into a smaller number of higher-intensity atmospheric river events.

Like the scales for hurricanes and other hazards, the rating scale for atmospheric rivers is based both its physical characteristics (wind speed for hurricanes, quantity of water vapor for atmospheric rivers) and on the level of destruction it causes.
While other rating systems are focused solely on the hazards of the event, the atmospheric river system incorporates the idea that these events can be beneficial, hazardous, or both. On the low end of the scale, AR Cat 1 events rated as primarily beneficial and at the high end, AR Cat 5 events primarily hazardous.
More about ➥ https://www.usgs.gov/news/new-scale-...c-river-storms

According to USGS natural hazards scientists, an atmospheric river-driven mega-storm that could cause catastrophic damage is plausible, if not inevitable, for California. Such a storm could cause extensive flooding across the state, raising environmental health concerns, causing thousands of landslides, disrupting critical infrastructure for days or weeks and causing 350 billion dollars in damages and 290 billion dollars in business interruption losses.
More about ➥ https://www.usgs.gov/programs/scienc...center_objects

[GordMay]

The storms hitting the NA West Coast, this past week are part of a “Pineapple Express” system [one kind of Atmospheric River, AR]; originating near Hawaii, and pulled toward the West Coast, by a rotating area of rapidly falling air pressure, known as a “bomb cyclone” [bombgenesis].

The NA west coast’s climate has long vacillated dramatically, from wet to dry, but models show these [wet↔dry] shifts will occur with increasing intensity, as the world warms. ARs are also becoming more likely to arrive in sets, which can cause up to four times more economic damage, than each would have individually, according to a study [1], published in Science Advances.

Supercharged by more moisture, coming off the Pacific, as ocean temperatures rise, scientists expect that ARs could also grow more severe, adding more risks for floods across California, and the west. As temperatures rise, precipitation is more likely to fall as rain, rather than snow, which could pose problems for the state’s water supply.

The term “bomb cyclone” was coined by a pair of MIT meteorologists, in a 1980 research paper [2], published in Monthly Weather Review. It didn’t catch on with the public, until January 2018, when a powerful storm blitzed the Northeast. The phrase is rooted in the word “bombogenesis,” which meteorologists and atmospheric scientists have been using, since the 1940s

[1]Temporal compounding increases economic impacts of atmospheric rivers in California ~ by Corinne Bowers et al
➥ https://www.science.org/doi/10.1126/sciadv.adi7905

[2] Synoptic-Dynamic Climatology of the “Bomb” ~ by Frederick Sanders & John R. Gyakum
➥ https://journals.ametsoc.org/view/jo...t_2_0_co_2.xml

[Don C L]

Yes but I don’t think this recent low we had was a case of a bomb cyclone as defined. I mean it didn’t seem to fall rapidly but I could be wrong. Maybe the speed of the fall is unimportant.

[GordMay]

Originally Posted by Don C L

Yes but I don’t think this recent low we had was a case of a bomb cyclone as defined. I mean it didn’t seem to fall rapidly but I could be wrong. Maybe the speed of the fall is unimportant.

The recent/current storm is due to an "atmospheric river" effect, which underwent bombogenesis.
By definition, a bomb cyclone is a low pressure system, that experiences a fall in pressure, of 24 millibars, in 24 hours.
➥ https://www.npr.org/2023/01/04/11469...r-bomb-cyclone

[Don C L]

Originally Posted by GordMay

The recent/current storm is due to an "atmospheric river" effect, which underwent bombogenesis.
By definition, a bomb cyclone is a low pressure system, that experiences a fall in pressure, of 24 millibars, in 24 hours.
➥ https://www.npr.org/2023/01/04/11469...r-bomb-cyclone

Thanks Gord, I missed that. I stand corrected!

[Montanan]

There are some major ocean surface temperature anomalies as of February 14, 2024.

Much warmer than normal for this date.

These temperatures in February are more typical of June, when hurricane season begins.

Reference article: Why a hot Atlantic has hurricane forecasters very worried.

https://www.msn.com/en-us/weather/to...1c2c959&ei=211

[jmschmidt]

Is Montanan in Hawaii of Aleutians? It is 2PM on Oahu and it will be lucky if we get 79 degrees f today. For months the temps have been mostly below normal. Right now, the ocean water 15 degrees warmer than the air.

We've had a few days in the mid 80's, then an unusual amount of wind, rain, flooding, trees falling, mud and rockslides blocking highways.

KYC has had 50-60K wind gusts with email warnings to members with boats at the Club or planning any voyages.

We have had three groups of mainland guests all of whom were shocked at the low temperatures and rain.

[Don C L]

“Right now, the ocean water 15 degrees warmer than the air.”

I think that may be the relevant part.

[Montanan]

Originally Posted by jmschmidt

Is Montanan in Hawaii of Aleutians? It is 2PM on Oahu and it will be lucky if we get 79 degrees f today. For months the temps have been mostly below normal. Right now, the ocean water 15 degrees warmer than the air.

We've had a few days in the mid 80's, then an unusual amount of wind, rain, flooding, trees falling, mud and rockslides blocking highways.

KYC has had 50-60K wind gusts with email warnings to members with boats at the Club or planning any voyages.

We have had three groups of mainland guests all of whom were shocked at the low temperatures and rain.

Are you anchored out along a north-facing shore? Sounds like spectacular surfing conditions and time well spent walking along the beach.

Grab you board and have a go before it calms down. The water is warm, come on it they said.

HIGH SURF WARNING IN EFFECT UNTIL 6 PM HST FRIDAY...

* WHAT...Surf 35 to 45 feet along many north-facing shores. Surf
20 to 25 feet along many west-facing shores of the smaller
islands except Maui. 15 to 25 foot surf impacting Big Island
north-facing shores Friday. 8 to 12 foot surf along Big Island
west-facing shores Friday. Swell timing has the highest surf
impacting Oahu from this afternoon through Friday...Maui from
later this afternoon through Friday...and Big Island from this
evening through Friday.


We will also be lucky in Montana today, only a winter storm advisory locally, cooling towards 9 F to night. The Mission mountains have a nice tropical glaze on them outside of town and there is considerably less ice on the Flathead Lake, now that it is 30 degrees warmer than a couple of weeks ago. The bays are still mostly frozen over. The water temperature remains a tad brisk at 34.7 F; all the rest of the thermometers of the buoy stations are measuring well below freezing so must be in ice.

Wishing you fine weather at Paradise, from us here in The Last Best Place.

[Montanan]

Here is a view of the surface water temperature anomaly that shows all of the oceans.

Hawaii has moderately warmer waters than normal.

[Montanan]

US Great Lakes Winter Ice Cover Averaging Just 5.9%: What This Means for 21% of Earth's Freshwater

https://www.msn.com/en-us/weather/to...e45c6ceb&ei=93

As of February 12, the Great Lakes reached a record-low ice cover of just 2.69%, CBS News reported. Lake Erie and Lake Ontario have tied their records for lowest ice cover, with records dating back to 1973, while Lake Huron, Lake Michigan and Lake Superior are at historic lows.

The 5.9% average is lower than the usual 40% average ice coverage this time of year, ABC News reported. Further, some parts of the Great Lakes have experienced winters without any ice cover.


No joy for ice boating, a busted season.