Tropical Storm Elsa: 8 July, Update A

I know I said I wasn't going to post any more on Elsa, but she's still hanging on as a pesky Tropical Storm and the NHC have actually bumped up her intensity even though she is over land... and I thought you might like to know what kind of magic this is (and if you don't, then that's ok, you can skip to the end of this... but you'll be wondering all night long what you missed, so you might as well read on. Grin.).

But first, she's at 36.3N, 78.3W, heading NE at a rapid 21mph and is currently near the North Carolina/Virginia border:

They just increased her intensity from 45mph to 50mph, which means she's still a weak Tropical Storm (TS range: 39-73mph), central pressure 1006mb. The speed was increased because some wind sensors detected speeds of just under 50mph, but she's not expected to get much stronger. 

Why is she getting stronger when she isn't over warm water? This increase is actually a result of what is going on in the atmosphere, not the ocean...

<Science Alert!> Vorticity: I haven't mentioned this yet this season, but now is as good a time as any to bring this piece of lovely jargon out for a spin. As you know, a storm has 'circulation', and it's pretty obvious what that is, right? It simply means that a storm is going around a central point, like a carousel. Vorticity, is essentially the way we measure the amount of circulation that a storm has. It's a very useful tool and I've used it for ages - next to a corkscrew for opening yummy wine bottles, it's my favourite (with a 'u') tool during hurricane season. ;-)

Although satellite imagery is one piece of the puzzle, the biggest clue about what sort of storm we have is the vorticity and what it looks like in different levels of the troposphere (see the Science Alert! here for a reminder of troposphere), because that gives us a glimpse into the structure of the storm. 

All types of stormy weather have a recognizable vorticity signal in the troposphere. Like a fingerprint, you can figure out what sort of storm system you have if you know what and where the vorticity is. The vorticity for low pressure fronts looks different compared to tropical storms. For low pressure fronts, the vorticity stretches out in a long line. For proper, grown-up, tropical cyclones, the vorticity is confined and generally circular. 

You can also tell how strong a tropical storm is depending on how strong the vorticity is and how high into the troposphere that signal can be seen. A Tropical Storm ALWAYS has a vorticity signal that reaches the middle of the troposphere (around 500mb) because this indicates that there is some deep convection (aka big thundery clouds). A Hurricane ALWAYS has a vorticity that reaches the upper level of the troposphere (around 200mb) because this indicates even strong convection and activity<End Science Alert!> 

Let's have a look at the vorticity maps for Elsa, shall we?

<Technical Alert!> Vorticity Maps:

Here is the vorticity map for 850 mb (almost the lowest level of the troposphere): 

You can see the signal of TS Elsa - the red (almost white) splodge (technical term ;-)), very conveniently almost covered by a Tropical Storm symbol. In this map, Green areas represent very mild vorticity, yellow is a little stronger, orange is fairly decently strong, red is very strong, and white is really super-duper strong! 

Now let's look a little higher in the troposphere. Here's the map for 500mb (the middle level of the troposphere):

You can still see the vorticity signal for Elsa, but it is a little weaker than the lowest level of the troposphere. Also, the center of the red/white splodge from the 850mb map is slightly offset from this orange/red splodge which indicates that the vortex isn't quite in alignment. This is frequently (but not always) associated with wind shear. 

And here's the map for 200mb (the upper levels of the troposphere):

In this upper level map, you don't see any signal for Elsa. That's because she's not a hurricane, or even close to being a hurricane - there is no upper level circulation. However, you can see a line of stronger vorticity that is fairly close to her - on the west side. That front is essentially giving her a little boost. So it's all in the atmosphere for this one. 

These amazing maps are produced by the University of Wisconsin-Madison's Cooperative Institute for Meteorological Satellite Studies - and a jolly good job they do too! To see them for yourselves in the future, click on the link above. Scroll down to the second map on the page (Regional Real Time Products) and click on the area of the world you are interested in. For the examples above, I clicked over the North Atlantic. From the drop-down menu, chose 'Winds & Analyses'. In the top panel, you'll see a whole array of buttons - including the 850mb, 500mb, and 200mb Vorticity. Clicking on those will give you maps like the ones above. This is one of my favourite websites and such a great resource for data! You can even go back in 3-hour chunks of time and see the vorticity for a storm evolve or move around. It'll provide you with hours of fun and entertainment - all from the comfort of your own living room! :-) <End Technical Alert!>

Because she has been over land, her convection has decreased quite a bit: 

There is still quite a bit of rain, but less of that very thundery/tornado like weather she had earlier in her life. Tomorrow in New England... 

So hold on to your Piglet! (and listen to your emergency managers because they have the best information for your local region). 

Toodle pip!

J. 

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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. 

Tropical Storm Elsa: 7 July, Update A

Well that was a pretty good day. I just finished watching the semi-final of Euro 2020 because I'm in England and that's what we do. It was England vs. Denmark and a very exciting match - England won 2-1 which means they will be playing against Italy in the final on Sunday!! It's been 55 years since they were in the final of this tournament - the last time they got this far was the 26th July, 1966 when they beat Portugal 2-1! History, baby! Woohoo.... and the TV commentator just told me to call my boss to tell them I won't be going in tomorrow morning because we have to celebrate all night... well ok, if I must.

I have to say, it's been years since I watched an entire football match (with overtime and additional minutes to boot!) and I'm jolly pleased to have watched this one. There are a lot of guys with very good looking legs that apparently don't work very well because they keep falling over. ;-)

You may be wondering if you have wandered into the wrong blog, expecting storms and getting a football update. No, you are in the right place... I have spotted the latest and greatest in wind sensor technology... 

Coincidentally, that seems to be about how strong the wind was in parts of Tampa Bay today as Elsa went by. She did regain weak cat 1 hurricane strength (75mph) as she passed  Tampa Bay, but that was only for about 6 hours or so before weakening again. 

Tropical Storm Elsa made landfall at around 11am local time in Taylor County, about 65mp NNW of Cedar Key, along the Florida panhandle close to the Big Bend as a strong Tropical Storm with winds of 65mph: 

She has of course weakened even more since then and is currently at 30.3N, 83.5W, over northern Florida and heading N to Georgia at 14mph. Winds are now 50mph, central pressure is 1002mb which means she is a weak Tropical Storm (range: 39-73mph). Her convection has decreased quite a bit since she made landfall, but that wind shear still exists and the bulk of it is to the east:

I know the official forecast calls for her to intensify again in a couple of days as she re-emerges over water, but I think she may fall apart as she crosses land. In addition to being over land (always a dodgy place for a tropical storm), there is also a teensy bit of wind shear between her current location and her emergence over water in northeastern US, and the water up there is a cool - surface temperatures are around 22-23 deg C (far too cold for any self-respecting storm). 

It looks like maximum storm surge was around 2.5 ft above normal (at Cedar Key for example), with most places reaching 1.5-2ft above normal. 

I got photos from our intrepid on-the-ground reporters in St. Petersburg, Chris K. & Peter R. (photo credit), whose Papaya Tree decided to have a rest from the soggy ground and heavy fruit.  

But other than that, no obvious wind damage (maximum recorded winds in St. Petersburg were around 25mph) - the mango tree still has its fruit in bags: 

Papaya and mangoes... I'm going over there for a visit! 

So, overall, she's mostly a rain event now as she crosses land. This is my last update on Elsa unless she does something crazy. Luckily she'll be long gone by Sunday... between the Wimbledon finals this weekend and the Euro 2020 Football Cup final, I don't know if I'll have time for storms! ;-) 

The next storm will be from the Flintstones... Fred. 

Toodle pip!

J. 

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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. 

Tropical Storm Elsa: 6 July, Update A

Another busy bees sort of day today (I say with ice cream beside me for er... brain food).

Our Tropical Storm du jour has crossed the Florida Keys and is now at 25.8N, 83W, heading N at a slower 10mph in the Gulf of Mexico:

Elsa emerged from Cuba and was a little stronger than the official forecast expected and is now a very strong Tropical Storm/almost cat 1 hurricane with estimated winds of 70mph, central pressure is 1000mb (TS range: 39-73mph).  She will most likely continue in this approximate strength of strong TS/cat 1 storm on landfall as expected yesterday and nothing too much stronger than that because the conditions aren't in place for intensification beyond that. You can see that she is under some wind shear in the satellite imagery because most of the convection is to the eastern side of her circulation:

Although she's lopsided, unfortunately for Floridians, the tougher weather is on your side - lots of rain, thundery weather, and possible tornadoes.

Storm surge is also increasing along the coast. To look for yourself...

<Technical Alert!> How to look up Storm Surge: Go to NOAA's website: tidesandcurrents (https://tidesandcurrents.noaa.gov/). If you click on this link, you will see an ugly cartoonish bad-suntan coloured map of the US (in shades of orange to represent the land - which, with the heat wave last week may just be the colour of land anyway these days!). Click on the state that you are interested in e.g. Florida. This will show you a much nicer colour map with a bunch of pins. These are the locations of the stations. You have to be careful though (if you are on a Mac especially) because the map is not static so you can accidentally scroll around and end up in the middle of the Atlantic, and will have to zoom out until the map you want re-appears and then zoom back in. Surely there must be a better map to use? 

You can either locate the nearest station by entering the area you are interested in, or zoom into the map. Click on that station, and in the lower left is a button that says 'plot'. Click that on and it will show you a plot of the expected water level (in red) and the actual measured water level (in blue). Here is the plot from Ft. Myers:

By scrolling your mouse over the plot, the numbers appear showing the actual values (and then you have to do some complicated maths to get to the difference between the two). In this case, you can see that the highest storm surge was actually about 0.63ft above normal a few hours ago and it is now returning to the predicted water levels. As Ft. Myers is up an estuary, I expect this is the storm pushing water into the estuary on the side where this sensor is located. 

If you want to see the corresponding winds, air pressure and other handy-dandy data, you can scroll down. So here, for example, is the pressure field which clearly shows the point at which the storm was closest to this location - which corresponds to the time in the water level plot above, when the storm surge (red) started to decrease towards the predicted level (blue) - because the winds were no longer pushing the water up against that side of the estuary. 

Having a quick look at other locations, water levels in St. Petersburg (my old home) is currently just over 0.5ft above normal and increasing (which is the case across most of Tampa Bay), and the pressure there is still decreasing as the storm gets closer, but Cedar Key to the north, which always has a higher storm surge is already at 1ft above normal - I assume their sensor is in a location which means water gets pushed up against it. <End Technical Alert!> 

And if you want to have a look at data offshore, check out the University of South Florida College of Marine Science COMPS network (these are the moorings I got my PhD data from a <ahem> couple <ahem> of years ago ;-)), which is part of the Southeast Coastal Ocean Observing System and the Gulf of Mexico Coastal Ocean Observing System:

The air pressure at the mooring closest to the Tropical Storm (C13) is currently reading 1002mb which is close to the levels the NHC are reporting, but winds are only just over 30mph though, so not quite the same intensity as being reported... I do see stronger winds at other moorings but I'm not sure this storm is quite as strong as they are estimating. This is a good example of why we need good observations off shore as well as a better understanding and data for storms in general! 

Listen to your local emergency managers because they have the best local information. Even with a strong Tropical Storm, remember, run from water, hide from the wind - which means that if you are in an area that floods, move to higher ground, otherwise hunker down. Most fatalities in storms are caused by water-related issues!

And I hope you are all prepared... here's a checklist from 2016, just in case (thanks Mark Z.):

Be safe my peeps!

Ciao,

J. 

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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 Storm Elsa: 5 July, Update A

Not much time for dilly-dallying today I'm afraid, so I'll just jump right into the fray (after I've had a sip of wine of course - priorities! ;-)).

Tropical Storm Elsa made landfall in Cuba a few hours ago (~6pm GMT) and is currently crossing Cuba. She's at 22.7N, 81.9W, heading NW at 14mph: 

She continued to stay on the southern (now western) side of the cone of uncertainty which is why the track is taking her to the northwestern part of the Florida Peninsula/Big Bend region. But this track also means she is crossing the narrowest part of Cuba, so she won't weaken too much. 

She is currently officially a weak Tropical Storm with winds estimated to be 50mph, central pressure 1004mb (TS range: 39-73mph) but they can't fly planes over Cuba so we don't have great data to verify that. They will fly a plane into the storm once she gets back into the Florida Straits to get a proper data update. Currently she is dumping a bunch of rain over parts of Cuba and the Cayman Islands: 

I think she may be a little stronger than the official forecast, but I agree with the NHC that she will most likely be a strong Tropical Storm (or very weak cat 1 storm) with winds around 65mph when she makes landfall. There are a couple of reasons she won't continue to increase in intensity once she is in the Gulf of Mexico. First, although she is going to be going over warm sea surface water, it isn't very deep and only the upper 50-75m is warmer than 26 deg C - this is important for storms because as they go over water, they churn it up and if it the warm water isn't very deep, they eventually churn up cooler water. And second, there is a bit of wind shear which will help to keep her in check.

For those along the west Florida coastline, watch out for storm surge as she spins by you. Storms are low pressure systems, and in the northern hemisphere that means water is pushed in an anticlockwise direction (or counter-clockwise if you prefer) around them. As Elsa goes by she will be pushing water onto the coast (and of course, if she is to the south of you, she will be helping water to move off the coast). And my other handy hint is that if she does stay in the center of that cone and makes landfall in the Big Bend region of Florida, there will be very high water levels (a few feet) in the Cedar Key area, so be prepared for that! 

Finished the wine, so I'll wrap up for now. Tune in tomorrow for more ramblings from moi (with some data and possibly an ice cream reference thrown in for good measure). 

Ciao for now!

J. 

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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 Storm Elsa: 4 July, Update A

Happy July 4th to those in the US - written from the UK, your friendly local provider of independence days to 58 countries. ;-)

Tropical Storm Elsa has been skirting the southern side of Cuba today and is currently at 19.8N, 77.9W, heading NW at a far more respectable 14mph:

She has been generally staying on the southern side of the cone of uncertainty and clipped Jamaica on her way to Cuba. It looks like she is still staying more on the southern side of the cone, so the downside to not traveling over land is that she is not going to fall apart as quickly as one would like, but the upside is that a lot of Cuba is spared from the brunt of the weather. Having said that, some parts are still getting a lot of rain and some thundery/tornado-like weather, as is Jamaica and the Cayman Islands: 

Her winds are 60mph, central pressure is 1009mb, which makes her a mid-size Tropical Storm (TS range: 39-73mph). The circulation in the lower half of the troposphere is still very good, which means she is a Tropical Storm. I also see some circulation in the higher levels of the troposphere, but it isn't as well developed as it would be for a hurricane. This is because there is still some wind shear. However, the upper level circulation suggests that if that shear decreases (which is quite possible), she could get a bit stronger before she makes landfall in Cuba tomorrow because she is also over some very warm water with the sea surface at 29 deg C and the upper ~125 m of the water is warmer than 26 deg C. She may be at or closer to being a hurricane again at landfall in Cuba.

More tomorrow, the start of the final week at Wimbledon. There may be a tennis reference or two that will sneak in when you least suspect it. 

Ciao for now!

J. 

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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 Storm Elsa: 3 July, Update A

The good news is that the wind is not howling (like this swirling storm inside) quite so much as before. That's right Elsa, Let It Go! (from Frozen, for the lucky uninitiated few amongst you!) ;-) 

There was some wind shear that kicked in today and that combined with some outer band interactions with Hispaniola means that she has weakened to a strong Tropical Storm with winds of 70mph (TS range: 39-73mph), central pressure 1002mb. We can see the land interaction in the satellite imagery now from the ragged formation of her convection:

It is difficult to see a center but she is currently at 17.3N, 73W, heading WNW at a whoppingly fast 29mph. As I said yesterday, it is unusual to see a storm moving so quickly in the tropics, but it is not unheard of. The last time it happened I think was in 2013 with Tropical Storm Chantal also in the Caribbean in early July, which had a forward speed of around 34mph at one point.

Her center is passing south of the southwestern tip of Haiti though, so once she gets away from the island she may strengthen a little bit more before getting to Cuba. The official forecast says she will continue to decrease in intensity and won't regain hurricane strength, although she will remain a mid-to-strong Topical Storm until she gets to Florida. I agree with this given her track looks like it will pass over Cuba. She may even fall apart a lot more quickly than the official forecast if she stays on the eastern side of the cone and over land - we've seen many storms fall apart crossing Cuba along this pathway. The more she interacts with Cuba, of course the weaker she will be. 

She no longer has any circulation in the upper levels of the troposphere, only in the lower half. This is consistent with a Tropical Storm versus a Hurricane. Also, there is continuing wind shear, so the circulation is a little skewed which means her vertical structure isn't very good either. 

And now I am going to have to go and listen to some proper music (i.e. ABBA) to get rid of the Frozen song from my head.

Toodle pip!

J. 

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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 Elsa: 2 July, Update A

I know, I know, you are wondering if I fell off this planet. I have no plans on traveling into space quite yet, although I did travel across time and space and am now on the Other Side of Elsa. 

I missed Tropical Storm Danny Boy, but he was another very short-lived storm of less than 24 hours and developed just off the S. Carolina/Georgia coast a few days ago. He was a Blot on their Landscape but hopefully brought some cooling drops of rain. 

Now for Elsa who popped up a couple of days ago and is officially the first Hurricane of the season with winds of 85mph, central pressure 991mb. This makes her a mid-size cat 1 storm (cat 1 range: 74-95mph). She crossed the Lesser Antilles today, near St. Vincent and St. Lucia, as a very weak cat 1 storm and is currently at 13.7N, 62.5W, zooming along in a WNW direction at 29mph... this is unusually fast for a hurricane and is one of the things throwing the forecast track off in the longer timeframes (4 and 5 days). In the shorter timeframe, she is heading towards the Dominican Republic and as she is in such a rush, she will arrive there tomorrow. 

I think there is a possibility that she will remain on the southern side of that cone of uncertainty, so she may actually not cross any land until she gets to Jamaica. We will know more tomorrow of course. If she doesn't cross land, she will get stronger because there isn't anything preventing her intensification - she is in a region of very low wind shear at the moment and over warm Caribbean waters with the upper 100-125 m warmer than 26 deg C. 

I expect she may be a cat 2 storm as she approaches Hispaniola and, again, depending on the exact track, there is actually a chance she will blossom to a cat 3 because the waters in that part of the Caribbean are warmer. Beyond that, it depends on the track she takes and how much she interacts with the islands. When she crossed the islands earlier today, she took a little hit which we can see in the infrared satellite imagery (ooh, I think I can hear Technical Alert bells in the background!) as the convection decreased: 

It looks like she is recovering from that now and is trying to get better organized - which we can tell from the cloud structure to the north of the center because it's got that lovely outflow pattern we see with hurricanes. Her circulation is really strong in all levels of the troposphere (ooh, the sirens of a Science Alert are also in the air!! :-)) which means she is definitely a hurricane. 

<Science Alert!> The Troposphere: Our atmosphere is divided into layers - like a delicious trifle (like the one sitting in the fridge in this house right now) or seven-layer dip. 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 layer of our atmosphere and extends up from the earth (ground zero if you like) to about 15-16km in the equatorial regions, and to about 8km in the polar regions of the planet. This is the layer of the atmosphere we live and breathe in. All our 'weather' essentially occurs in the troposphere. The troposphere is defined by decreasing air temperature with increasing height. You would know this 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 increasing with height. The ozone hole is in the stratosphere. The top of the stratosphere is around 50km height and is marked by the stratopause. And the layer above that is mesosphere, where air temperature decreases with height again until the mesopause. Above that is the thermosphere, then the exosphere... and then we get to space, which is where I hear a few people will be heading later this month.<End Science Alert!>

A Science Alert! followed immediately by a Technical Alert! It is our lucky day! ;-) 

<Technical Alert!> It's really useful to know that temperatures decrease with increasing height in the troposphere. This gives us a clue about how strong a storm and it’s convection (rain, thunder etc.) is from the satellite images. The satellite imagery above is the infrared imagery and shows the temperature at the tops of the clouds. Higher cloud tops means a more turbulent atmosphere and stronger convection, but it also means colder cloud top temperatures. The red areas are the coldest cloud tops and they correspond to very heavy rain, strong winds, a lot of thunder, tornadoes… basically everything and the kitchen sink (but not the trifle). Orange areas are less strong – thundery weather, strong winds, heavy rain. Yellow would be strong winds and rain, green is mostly rain with some wind, and then it gets to light rain/just cloudy where we see blue and gray.<End Technical Alert!>

You will all be quizzed tomorrow so I hope you were paying attention. ;-) 

I think that's all from this side of the pond... I'll be back tomorrow. It's wine-o-clock here (well, it's been wine-o-clock here for the last couple of hours actually...). 

Toodle pip!

J. 

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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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