Saturday, November 21, 2020

Not One Iota: November 20, Update A

Now THIS is what I call a good Friday evening... 

Iota did fizzle out a couple of days ago - well done El Salvador for putting a stop to that one! Hurricane Iota was the 2nd cat 5 hurricane in the month of November (the first known one was in 1932 and hit Cuba). The extent of the damage is not known, but over 50 people lost their lives and almost as many are still missing. This is my last update on Iota.

I've had a few queries about hurricanes in December, and it is possible. Time for a Science Alert! Oooh... it maybe the last hurricane science alert of the season so you better make the most of it! ;-)

<Science Alert!> The Atlantic Hurricane season which runs from June 1 to November 30 is based on statistics - around 97% of all hurricanes occur in those 6 months. Which, of course, means the other ~3% occur in the other months.

Here is a figure I made in 2006 that shows the track of all storms from 1851 to 2005, divided into the month they formed (graph credit: MOI ;-))

You can see storm tracks in all months - even February and March! So, it is statistically possible for something to pop up in December (but it would be really nice if we were done for the year now!). 

The other interesting thing this shows is that early in the season and late in the season, storms pop up closer to the Caribbean/North America, whereas from July - September, they come over from the eastern Atlantic. So to have storms pop up in the Caribbean like Eta and Iota did at this time of year is the norm - it's the intensity that is on the severe end of the spectrum, although not unheard of around this time of year as we know from the 1932 cat 5 Cuba Hurricane, and even Hurricane Wilma in 2005, which was a late October cat 5 storm. <End Science Alert!>

That's it for today until the next one (which would be Kappa - hopefully not) or the end of the Hurricane Season (which will be in 10 days - hopefully). 

Toodle pip!

J. 

Twitter:  jyovianstorm

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DISCLAIMER:
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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Wednesday, November 18, 2020

Tropical Storm Iota: November 17, Update A

I suppose it fits the theme of 2020 to be witness to the one and only Hurricane Iota that will ever exist, and that too a cat 5 storm! Even though we barely have any idea of the damage this has caused a day after landfall, I'm sure they will retire this name after this season.

Here's the satellite imagery from landfall to present, showing the decline:


Officially, it is now barely a Tropical Storm with winds at 40mph, central pressure 1000mb (TS range: 39-73mph). 
At the moment it's about to cross into El Salvador from Honduras and is currently at 13.7N, 87.3W moving W at 12mph. 

And the forecast shows that it will weaken and fizzle out by tomorrow morning. But hmm... I do see that it still has a very strong vorticity signal throughout the troposphere... hmm... I wonder if it's actually stronger than the official intensity suggests, in which case there is a chance that it may cross over into the Pacific and re-form. We'll know in a few hours if El Salvador manages to finish it off or not because it's officially supposed to be a Tropical Depression by tomorrow morning. 

I was planning to sign off on Iota today, but I guess I'll be back tomorrow to wrap this one up.

Toodle pip for now,

J. 

Twitter:  jyovianstorm

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DISCLAIMER:
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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Monday, November 16, 2020

Hurricane Iota: November 16, Update A

Definitely a double lychee martini night! 

Hurricane Iota officially made landfall as a borderline cat 4/cat 5 storm with winds of 155mph near the town of Haulover, about 30 miles south of Puerto Cabezas and just 15 miles from where Hurricane Eta landed only 13 days ago as a cat 4 storm! 

Although this was officially a cat 4 storm with winds of 155mph (central pressure 920mb) after the entire eye had made at landfall (cat 4 range: 130-156mph), it was actually a cat 5 when the western eyewall made landfall about 3-4 hours earlier with winds of 160mph, central pressure was 918mb (cat 5 range >156mph). 

The storm has already started to weaken - we can see that the eye is smaller and the convection (which is still strong enough to spawn tornadoes) is weaker than a few hours ago.  

It is now at 13.6N, 83.4W, heading W at 9mph.

It will remain a hurricane as it crosses Nicaragua, becoming a Tropical Storm as it gets closer to Honduras tomorrow evening. We won't know the full extent of the damage, but I will stop by tomorrow with an update. What an awful mess this is going to be though! 

Ciao,

J. 

Twitter:  jyovianstorm

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DISCLAIMER:
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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Hurricane Iota: November 15, Update A

Ice cream in bowl so I'll jump right in (to the update, not the bowl... although... hmm... ;-)). 

Iota is now officially a strong cat 2 hurricane with winds of 105mph, central pressure 960mb (cat 2 range: 96-110mph) and will soon be a cat 3. There is no wind shear so we see a really beautifully structured storm with good outflow in all quadrants of the system... 


The eye has been really clear and well developed for the past hour at least and I actually think this has already reached cat 3 status with winds close to 115mph. You can also see that coastal areas of Nicaragua and a small part of Honduras are already getting some heavy rain in the outer bands. It's expected to be mid-size cat 4 storm as it approaches the coast (the same intensity as Hurricane Eta when it made landfall on Nov 3). 

It is at 13.3N, 80.2W, heading W at a decent 10mph. The one major difference between this and Hurricane Eta as it approached Nicaragua a couple of weeks ago is that this one is moving at a reasonable pace, whereas Eta was a really slow moving storm when it was just off the coast. 


Landfall is expected to be overnight tomorrow (Mon/Tues). This is a pretty hilly area, so as with Eta (and Hurricane Mitch all those years ago) we can expect landslides unfortunately. 

As I mentioned, there is absolutely no wind shear at the moment and it doesn't look like there will be any before landfall. The sea surface is 28-30 deg C between here and landfall, with the upper ~100m warmer than 26 deg C, so there is plenty for it to use to grow. There is a bit of dry air but only in the lowest sections of the storm so I'm not sure it's going to make a huge dent - which means that the only thing that is going to stop this one from getting stronger is the interaction with land. 

It has a really good structure throughout the atmosphere, which we can see from the satellite imagery above, but also in the vorticity maps, which shows that the circulation is really strong in all levels of the troposphere. Here's the vorticity map from the lowest level (850mb) - you can clearly see the storm... 


Here's the map in the mid-troposphere at 500mb: 


And here it is in the upper troposphere, at 200mb: 

I read that evacuations started a couple of days ago so I hope that will help to mitigate the damage! Wishing everyone in that part of the world a safe few days. 

Ciao for now, 

J. 

Twitter:  jyovianstorm

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DISCLAIMER:
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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Sunday, November 15, 2020

Tropical Storm Iota: November 14, Update A

A rather quick note for today on our troublesome Tropical Storm Iota, which was named yesterday.

It's now at 12.7N, 77W in the Caribbean and is heading W at a rather slow 5mph. 

I call it troublesome because it's on a similar path as Eta - expected to intensify into a major hurricane and then go into Nicaragua and Central America. They are already struggling to recover from Hurricane Eta in that part of the world so if this pans out, it's a major disaster in the making. 

Winds are currently 70mph, central pressure is 990mb, which means it's almost a cat 1 storm (Cat 1 range: 74 - 95mph). 

The vorticity is really good in the lower half of the troposphere, but there is also a signal in the upper troposphere now which suggests to me that Iota is already a weak cat 1 hurricane. We can already see that the convection has improved a lot in the last few hours... 

There's no eye yet, so winds are definitely not over 85mph yet. Unfortunately there is barely any wind shear and the water is very warm, and there is very little dry air - all the signs are there for intensification and I agree with the NHC that this will be a hurricane tomorrow. It may even be  a major one (cat 3 or higher) by the end of the day. 

Iota by name, but not Iota by nature... there will be a lot more on this one for sure! 

Ciao for now,

J. 

Twitter:  jyovianstorm

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DISCLAIMER:
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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Friday, November 13, 2020

Tropical Storms Eta and Theta, and the Caribbean Blob: November 12, Update A

I heard from lots of you as Eta went by and today - I hope all gets righted as quickly as possible! It made landfall at around 4.20am today, about 5 miles north of Cedar Key, FL as a fairly weak Tropical Storm with winds of 50mph. Luckily for them the maximum storm surge was about 3ft above normal and occurred at low tide, so not as much of a problem as storms of times gone by. 

Tropical Storm Eta

But for a fairly weak storm it caused quite a problem, mostly water related as expected, which unfortunately resulted in a number of deaths in FL and in NC (from flash floods). 

It's now over the Atlantic at 32.3N, 79W, heading NE at a pretty quick 17mph.


Winds are now down to 45mph, central pressure is 1004mb, which makes it a very weak Tropical Storm (TS range: 39-73mph). There isn't really much of a storm - the convection is just from being over warm water. 


The storm has now pretty much merging with a front, which you can see from the vorticity maps. Here's the lower troposphere at 850mb: 

middle of the troposphere at 500mb: 


You can see the long stream of vorticity (circulation) along a northeast/southwest angle.

This is one storm name that will get retired - in addition to the havoc in the US, this is the same storm that hit Nicaragua (seems like weeks ago!) and Central America where, sadly but not unexpectedly, its flooding caused over 120 deaths, hundreds are still missing, and millions are severely affected in Honduras and other countries in the area. 

This will be my last update on Eta.

Tropical Storm Theta

Officially this is at 31.7N, 26W, heading E at 12mph towards the Canary Islands for the weekend (don't we wish we all were?), where it will hang out and dissipate. 


Winds are currently 60mph, central pressure is 993mb, which means it's a mid-size Tropical Storm. This one got some of it's energy from the atmosphere all along, so at the most I'd let it be a Subtropical Storm now, but even that's a little dodgy as the vorticity maps show that in the mid-levels of the troposphere the circulation is connected to a line of strong vorticity. There's no way that strong a system is purely driven with energy from water which is 22-23 deg C! 

Satellite imagery shows some circulation but very little convection, but we see this sort of thing in many winter storms (over cooler water temperatures): 


I think this will be my last update on Theta as well unless it does something wonky before getting to the islands. If you are out there, it'll be more of a windy thing than a water event. 

Caribbean Blob

You do know we have a few weeks before the statistical end of the Hurricane Season, don't you? ;-) SO....

... there is a blob which now has an 80% chance of developing into a storm in the next 48 hours. You can see it quite clearly in the vorticity maps - it has circulation in the lower level and is actually a little better structured in the mid-level compared to Theta. To me, this suggests it's already a Tropical Depression, and maybe even a weak Tropical Storm by now. The convection isn't quite there yet though:


This may be the future Iota... and hopefully it will just be an iota of a storm because one possible path is towards Nicaragua & Honduras! 

That's it for now. I'll be back when the next one develops. So, most likely tomorrow. 

Toodles,

J. 

Twitter:  jyovianstorm

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DISCLAIMER:
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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Wednesday, November 11, 2020

Tropical Storm Eta: November 11, Update A

A little earlier in the day today because of Tropical Storm Eta (I'm ignoring Theta for today), so no wine, but I have a nice cuppa tea. :-) 

Eta, on the other hand, is going to make landfall north of Tampa Bay tomorrow morning. It is currently at 27.9N, 83.4W, heading N at a respectable 12mph. 

They did upgrade it to a cat 1 hurricane, but it has weakened because of that dry air I mentioned yesterday and is now a strong Tropical Storm with official winds of 70mph, central pressure 993mb (TS range: 39-73mph). It's lost a lot of convection this morning because of that dry air, but it looks like that is decreasing now as there is more convection in the last few hours: 


The circulation (vorticity) is really strong in the lower half of the troposphere, but a little removed in the upper level so it's in keeping with a strong Tropical Storm. It continues to be in some wind shear with the clouds mostly on the eastern side, which is also keeping it in check of course. 

Luckily I did jinx it and it's by-passing Tampa Bay now, but the angle of this storm means that the water will be pushed into the Bay so there definitely be flooding in all the usual places. Storm surge from tidesandcurrents.noaa.gov show (for example), in St. Petersburg, the water levels are over 3ft above normal... 


And Old Port, Tampa is showing water 3,5 ft above normal.

Eta is passing by TB - here's the pressure from the St. Pete station: 


The peak winds recorded were around 33knots = 38mph, so not Tropical Storm force in that location.  

The current path looks like landfall will be close to Cedar Key... historically, Cedar Key is prone to flooding. I've seen early season Tropical Storms like this that result in 8ft or so storm surges there... so if you are there, get ready for a water event rather than a wind event. It's already about 2.5ft above normal. 

There are buoys off the west Florida coast (I should know as that is where my PhD data came from :-)) - operated through the College of Marine Science, USF, and part of a US-wide network of extremely useful and valuable coastal ocean observations. One of them (closer to Tampa Bay) is showing winds of around 40mph, air pressure of 1002mb, however a mooring farther offshore recorded a low pressure of 993mb, which corresponds to the official NHC air pressure in the center - which suggests that the center may have passed right over this location.

I agree with the NHC that this storm will continue to weaken before landfall. It's really going to be a storm surge/water issue than wind I think - although be careful as trees knock down power lines which don't mix well with water! And of course, listen to your Emergency Managers. 

Wishing everyone a good Veterans Day and Remembrance Day - depending on which country you hail from! 

Be safe out there! 

J. 

Twitter:  jyovianstorm

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DISCLAIMER:
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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Tropical Storms Eta and Theta: November 10, Update A

Another a busy day today but I have my glass-o-wine, so jumping right into the fray... 

Tropical Storm Eta

It's currently at 23.8N, 84.5W heading NNE at 9mph. It's made that u-turn and is now on the northward track with landfall on the west Florida coast on Thursday. I have to go with the NHC track, but we are still over a day from landfall (they are usually far more accurate at one day before landfall), so remember to keep an eye on the cone - it could go anywhere in that area - and the track can still change and shift some more. I don't have the same good data that I used to be able to access, but I'd be prepared for it to move towards Tampa Bay (of course, now I've said that it will go the other way, won't it? ;-)). 

As expected, it is a strong Tropical Storm with winds of 65mph, central pressure is 992mb. I think it's actually a cat 1 hurricane now though as we can see a very small eye in the satellite imagery that's coming in and out of focus:

This suggest that winds are somewhere in the 80-90 mph range. The outer bands are back over the Keys and it looks like a lot more rain this time around. 

There is some vorticity throughout the troposphere, but it's not very cohesive - the lower level is offset from the upper level. This indicates that a little wind shear is in play, which we can also see in the satellite imagery as there are more clouds are fractionally greater on the eastern side of the storm. But it looks like the wind shear is dying down, alas, so that won't be inhibiting this for the next day at least. 

It is moving over water that is just over 27-28 deg C in temperature, which is enough to keep this storm going. At the moment the upper ~100m of the water is warmer than 26 deg C, however, by the time it gets off the southwest Florida coast (by tomorrow evening) the water will be a little cooler (still over 26 deg C), but the warm water won't be as deep so that means there shouldn't be any rapid intensification and it may actually weaken before landfall. 

There is some dry air to the west and in the lower levels of the storm, but it's not yet clear if this will be enough to slow the storm down in the next 24 hours. 

So, if I were still living in St. Pete, I would get ready for a cat 1 hurricane. The hope is that it will be weaker, but there are a couple of competing influences. 

"Tropical" Storm Theta

This is currently at 29.4N, 35.5W, heading ENE at 12mph:  

Winds are officially 70mph, central pressure is estimated to be 989mb - this officially makes this a very strong Tropical Storm (TS range: 39-73mph) and almost a cat 1 hurricane. But as I said yesterday, this does not have the vorticity structure of a tropical storm in the troposphere but is rather a segment of a low pressure front. 

The satellite imagery shows some circulation (but we see that in the winter months with low pressure systems anyway) but with very little convection:


 
It may try and develop some more tomorrow, but I don't see any reason why as the water temperatures are cold and there is a lot of wind shear.

That's it for today. I'll be back tomorrow - and I'm sure you are ready in Florida... wine, ice cream, wine, more ice cream, candles, a radio with batteries, a good book or two etc. Remember to listen to your Emergency Managers!

Toodle pip!

J. 

Twitter:  jyovianstorm

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DISCLAIMER:
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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Tuesday, November 10, 2020

Tropical Storm Eta and Subtropical Storm Theta: November 9, Update A

Well well, the most 'named' storms in a season hey? This season now ties with 2005 for the most named and numbered storms on record - 30. 

<Minor Rant Alert!> However of course back then in the days before satellites some of the storms in today's day and age would not have been detected - or even noted as being significant by the NHC - especially not very short lived few hour storms such as 2020's Subtropical Storm Alpha which was a named system for less than 12 hours and only had winds greater than 39mph for about 5 hours!! That's just a blob at that point! I'll do a proper analysis of this season once it's over, but I definitely don't agree that all the storms named this season were proper storms which is really annoying because it masks the actual trends when things are named willy nilly and it messes up the scientific conclusions! To get around this, the NHC need to introduce a process for 'un-naming' storms in such cases!<End Minor Rant Alert!>

Tropical Storm Eta

It's still officially a Tropical Storm and the entire forecast was downgraded from Hurricane to Tropical Storm for its lifetime. I'm not sure I'm in complete agreement with this downgrade but I'll come to that later. 

It is currently at 23.2N, 85.2W, heading SW at 9mph: 

The forecast is that it will continue south for a little longer and at a slower pace before doing a bit of a u-turn and heading back to the north. 

Winds are currently 50mph, central pressure is 995mb, which makes it a weak Tropical Storm (TS range: 39-73mph). However, the convection has definitely picked up in the last few hours: 


This is because it's over some very warm water (sea surface temperatures are warmer than 28 deg C), and also over the teeny little bit of Loop Current where the upper ~125m of the water column is warmer than 26 deg C:


This suggests to me that this is not a weak Tropical Storm anymore, but a strong one, possibly with winds of around 65mph. I think there's a small window for it to become a cat 1 storm before it gets too far into the northern Gulf where it will run into a couple of things that will knock it down a notch. 

You can see from the map of the warm water above that in the northern Gulf, the warm water is be shallower - that's one factor indicating that it should get weaker.  

There is also very little wind shear at the moment, which is why it is developing. However the northern and eastern Gulf has quite a bit of wind shear - another weakening factor as it moves north. 

There is some pretty good vorticity throughout the troposphere at all levels. It's not very well defined as we've seen in all the other Tropical Storms, but it's definitely more confined and distinct than the interloper Theta (see below)!  

For your reference, the vorticity map in the lower troposphere (850mb) is:


The vorticity map in the middle troposphere (500mb) is:


And the vorticity map for the upper troposphere (200mb) is:


This brings me to...

Subtropical Storm Theta

Sigh. I can't believe they think this is tropical in any way and went ahead and named this one at this stage. They must have drunk too much champagne this weekend!

As you can see from the vorticity structure above, there is no part of the troposphere that has a tropical storm signal in any way - it's all a front (an elongated line of vorticity - the long red streak that is stretching to the northeast from the subtropical storm symbol in the middle of the Atlantic). They are calling this a subtropical storm because it's getting it's energy from the atmosphere, not from the ocean.  A tropical storm needs water warmer than 26 deg C to get its energy from the ocean - the water temperature under Theta is too cold for a tropical storm and is around 23 deg C at the surface. You can also see that there is no water warmer than 26 deg C from the water depth map above. 

Still, it's another one that's been named when it shouldn't have been and that's what we have now. It's at 28.8N, 40.3W, heading E at 15mph. 


Officially winds are 50mph, central pressure is 1000mb, which officially makes this a weak Tropical Storm - the same level as Eta actually, even though Eta is clearly stronger! As for looks... 


It also looks nothing like Eta - at least not today. Clearly there is a lot of wind shear and you can see the front - the straight line of clouds. This is really not a Tropical Storm by any means - but we'll see what happens tomorrow. The NHC think that it will develop into a TS by then. Hmm. 

That's it for now!

Ciao,

J. 

Twitter:  jyovianstorm

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DISCLAIMER:
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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