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2021 Hurricane/Typhoon Season

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This thread will consist of written discussions on tropical/subtropical cyclones across the world. Primary focus will be on TC/s that pose threats to land. Check out this short video for introduction of TCs.


Abbreviations:

SST - Sea Surface Temperature

VWS - Vertical wind shear (typically 200-850mb shear)

LLCC - Low Level Circulation Center

OHC - Ocean Heat Content


Useful Links:

CIMSS

National Hurricane Center / Joint Typhoon Warning Center (JTWC)

Tropical Tidbits

Weather Nerds

Real Time Tropical Cyclone Products

Statistical Hurricane Intensity Prediction Scheme (SHIPS)


Past discussions:

Before 2020

2020


Regular updates on tropical cyclones

I mainly focus on WPac and NATL basin.

Response to 2021 Hurricane/Typhoon Season 2020-12-26 14:37:47


There are no hurricanes & deadly poisonous spiders, snakes in my country, so I guess I'll just show myself out


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Despite the narrative, there is no obvious change in global tropical cyclones ACE (a measure of tropical cyclone activity).

This however, should not be interpreted as a positive evidence that global warming has no measurable impacts on regional TCs.


iu_229950_779242.png

Climate models have predicted increased activity in the North Atlantic basin in the next few decades and past records (say starting from 1989 as a comparison), could suggest a gradual upward trend. It is unclear how much role global warming has played, since the last couple of decades also had positive AMO which tends to enhance tropical activity.


It may not be possible to separate the influence of general warming from the influence of positive AMO.


The models also suggest the possibility of a downward trend in terms of tropical cyclone numbers in the Pacific that partially offset the increase in peak intensities.


Regular updates on tropical cyclones

I mainly focus on WPac and NATL basin.

Response to 2021 Hurricane/Typhoon Season 2021-01-24 08:55:18


I'd just love it if all of the hurricanes could not come to Louisiana this year. That'd be great.


I saw a graphic where they put cones for every storm we had last season and they pretty much all came here.


Let's spread that shit out this year, thanks.


| It is possible to commit no mistakes and still lose|||Love belongs to Desire, and Desire is always cruel.||||

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Response to 2021 Hurricane/Typhoon Season 2021-01-24 09:52:29


At 1/24/21 08:55 AM, SevenSeizeHasCookies wrote: I'd just love it if all of the hurricanes could not come to Louisiana this year. That'd be great.

I saw a graphic where they put cones for every storm we had last season and they pretty much all came here.

Let's spread that shit out this year, thanks.


Did someone in your vicinity piss Thor off somehow?


You can't fight for peace. If you fight, there ain't peace. NO, I'M NOT AMERICAN!

On every ship that floats and sails, there's someone who the captain nails.

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Invest 91W (West Pacific)


Across the tropics, low level westerlies remain in place in the West Pacific sector due to combined signal of La Nina, MJO and an equatorial Rossby wave, creating a potential area for tropical cyclone formation in the upcoming week.

iu_242473_779242.jpg


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An area of low pressure (Invest 91W) is now located over 500 miles east of Mindanao, Philippines. The low pressure area has been producing persistent disorganized central convection. Satellite image shows an east-west elongated LLC with winds up to 20 knots. The system has not changed much in organization over the past 24 hours.


The system will track slowly westward in the next several days along a weak extension of the low level subtropical ridge, closer toward the Philippines. Upper level flow is marginal for significant intensification with moderate (15-20kt) of southerly VWS, offset by strong poleward outflow. Global models generally depict slow consolidation over the next couple of days, with the possibility of attaining tropical depression status beyond 48 hours, as the surge of the northeast monsoon interacts and strengthens its wind field.


The likelihood of a significant TC formation is high and the system could become a tropical storm of 35-40kt prior to landfall over the Phillipines.


Regular updates on tropical cyclones

I mainly focus on WPac and NATL basin.


Tropical Storm Dujuan (91W -> 01W)

iu_243526_779242.jpg

The low pressure area developed a sufficiently defined LLC and organized convection for classification as a tropical cyclone. At 12z, the tropical storm is located approximately 300 miles east of Mindanao, Phillipines. A much earlier ASCAT pass shows broad swarth of 30 knot winds in the western quadrant. Subjective Dvorak classification is currently at T2.5/35kt, justifying an upgrade to a tropical storm of 35 knots. The system has tracked westward slowly inside an area of weak steering currents.


Animated visible imagery depicts a partially exposed LLC with deep convection confined to the northwest of the center, a result of persistent moderate SE'ly VWS (15-20 knots). At the same time, the mid-level center, while still being displaced westward, is now closer to the pocket of convection and the LLC, indicative of a slow consolidation trend.


As the system will remain on the southwestern periphery of a 200hPa anticyclone across the Pacific, VWS will continue to hamper development. By 60 hours, the system will reach a peak intensity of 50 knots and begin to make landfall over central Philippines on a northwesterly track.


iu_243527_779242.png

In the extended range, TS Dujuan will move across the central part of South China Sea. VWS is expected to exceed 30 knots by then and the system is likely to degenerate into a low pressure area during recurvature to the north.


Regular updates on tropical cyclones

I mainly focus on WPac and NATL basin.