Tuesday, September 20, 2022

September 19, Update A: Hurricane Fiona

Oh dear oh dear oh dear. I was busy watching historical events in the UK (including, along with a few billion others, the 'biggest live TV event in history' today) so I wasn't paying attention to the Atlantic! To make up for it, I will write extra long and possibly even slightly interesting updates for the next few days. So to start... I see that Hurricane Fiona has been a bit of a menace in the Caribbean (not like my friend, Fiona, who is (a) a lovely person and (b) not in the Caribbean). And it looks like she (the storm, not my friend) will continue to be troublesome for a few more days. 

She was named Tropical Storm Fiona 5 days ago and crossed into the Caribbean just north of Guadaloupe as a mid-size TS with winds of 50-60mph on Friday. 

Fiona (the storm, not my friend) became a cat 1 hurricane as she was passing south of Ponce, Puerto Rico, and made landfall yesterday on the very southwestern tip of Puerto Rico, about 15 miles SSE from Mayaguez - still as a cat 1 hurricane with winds of 85mph, central pressure 986mb. This September marks the 5 year anniversary of Hurricanes Irma and Maria hitting Puerto Rico and unfortunately the infrastructure is still not robust so as a result power has, of course, been knocked out.

After Puerto Rico, Island-hopping Fiona briefly visited the Dominican Republic this morning, still as a cat 1 storm with winds of 90mph, but is now on her way to see what's happening in the Turks & Caicos. I hope the peeps on the islands in the northern Caribbean are generally ok - this storm just dropped a lot of rain all over the place! Stay safe out there my friends! 

She is currently at 20.6N, 70.3W, heading NNW at 10mph and has intensified to being officially a borderline cat 2/cat 3 storm with winds of 110mph, central pressure 971mb (Cat 3 range: 111-129mph). The track, as I said, takes her north now to the eastern Turks & Caicos, and then into the Atlantic heading generally towards Canada - but making sure to try and take in Bermuda on her journey:

It is possible that she will pass to the west of Bermuda instead of directly over the island, but definitely expect windy and wet weather. 

As we can see from the visible satellite imagery, she has a lovely eye and quite a lot of very strong convection (which we can see from the red areas in this infrared satellite imagery which are areas of strong tornados, lightning and stuff - stormy stormy weather): 

Her circulation is also quite strong throughout the troposphere (ooh... Science alert! :-)) so I agree with the National Hurricane Center (NHC henceforth) that she is a cat 2, borderline cat 3 storm (actually, I think she's already a cat 3). 

<Science Alert!> The Troposphere. Our atmosphere is divided into layers - like a delicious strawberry trifle or seven-layer dip or lasagna (depending on which country you are from). In each layer, the air temperature either increases with height or decreases with height. The troposphere is one of these layers. It is the lowest section of our atmosphere and extends up from the Earth (or Ocean :-)) to about 15-16 km in the equatorial regions and to about 8km in the polar regions of the planet.  This is the layer of the atmosphere we live in - this is the layer we breathe. All our 'weather' essentially occurs in the troposphere. 

The troposphere is defined by decreasing air temperature with increasing height - something you would have experienced already if you climbed a mountain. Or the easier option, of course, is to just look at pictures of mountains and see the snow at the top (known as the 'Flat Florida Option'). ;-) The top of the troposphere is called the tropopause. Strong tropical storms have clouds that reach as high as the tropopause - and in a few very strong cases, they can extend even higher into the next layer up - into the stratosphere, which is the layer of the atmosphere above the troposphere. The stratosphere is defined by air temperature that increases with height. The ozone hole is in the stratosphere. The top of the stratosphere is around 50km height as is marked by the stratopause. And the layer above that is the mesosphere, where air temperature decreases with height again... and so we go on until we get to space... <End Science Alert!>

The NHC think she will continue to intensify to a cat 4 storm, and it looks like that is quite possible. She is over some very warm water - sea surface temperatures are warmer than 28 deg C, and the upper ~100m of water is warmer than 26 deg C, which means that she has a lot to feed her. She is moving into an area where the wind shear is getting weaker, which gives her a chance to intensify. The only thing I see at the moment working against her a little is that she has some dry air to her west, which could keep her in check a bit. We can see this from the water vapor imagery where the yellow parts are drier air: 

That's Fiona for today.

Since we last met, Tropical Storm Kay peeked over the Los Angeles horizon! A very rare occurrence indeed. It's been 9 years since I sat under a tropical storm so it was quite refreshing (like my G&T) to be in the rainy and cloudy weather in Los Angeles, where we saw the outer bands of Tropical Storm Kay. At least where I am, she brought much needed rain to this part of the world which is facing a drought (355 days of the year there is no rain in LA, so of course that was the day our roof had work done on it... impeccable timing! ;-)). Kay has long gone but, although not unheard of, I read that this was the closest a tropical storm has reached Southern California in about 50 years. 

Until tomorrow!
Toodle pip,

Blogs archived at http://jyotikastorms.blogspot.com/

Twitter @JyovianStorm



These remarks are just what I think/see regarding tropical storms - not the opinion of any organization I represent. If you are making an evacuation decision, please heed your local emergency management and the National Hurricane Center's official forecast and local weather service announcements. This is not an official forecast. If I "run away, run away" (Monty Python), I'll let you know.

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