Tropical Storms Florence, Isaac, and Helene: September 8, Update A

It's a busy travel day, so that means lychee martini day. Obviously. Our Constellation of Storms is still in place... 

And from the satellites, this looks like:

TS Florence

Florence is currently officially the strongest of the three, with winds of 70mph, which means she's close to being back to a cat 1 hurricane (cat 1 range: 74-95mph). Her central pressure is 989 mb. She's currently at 24.6N, 54.7W, heading W at a very slow 5mph. 

She's moving slowly because there's a high pressure in front of her that is slowing her down (it's like climbing up a hill - and I just got back from walking around Atlanta, so I know what that's like!). And she's moving W because she's skirting a high pressure area to the north of her. I know her forecast track looks scary: 

You guys in Georgia and the Carolinas should all be ready as it really is waaay too soon to say quite where she'll go. I agree with the ~1 day forecast on the track at the moment, but I don't have the data (because we don't measure it) to be able to say what it will look like beyond that (and although I'm on travel, I'll check in once a day somehow as you are my peeps!). 

In case you are wondering which one she is when you look at the satellite images, she's the tiniest of the swirling masses - the one that's around the same latitude as southern Florida. I know it doesn't look like she's the strongest of the three, but officially she is because a plane flew in and got some of valuable data, and those are the winds that the NHC have deemed her to have. Please note, a plane has not flown into the other two storms as they are too far away - this will feature later in this blog (spoiler: I really disagree with the intensity they have for the other two). 

Let's look at her structure - the circulation (vorticity). Here's the vorticity (circulation) at 850mb (lowest level), 500mb (mid-level), and 200mb (upper level): 

You can clearly see that the circulation is good for Florence in the lower half of the troposphere (up to 500mb), but there isn't a good defined feature in the upper troposphere, which indicates that her structure isn't quite so strong as a hurricane yet, so she is still definitely a Tropical Storm. For those who are taking a sneak peak at the other two storms... which one do you think is the strongest?

TS Isaac

He's officially a fairly weak TS with winds of 50mph (TS range: 39-73mph), central pressure 1002mb. He's currently at 14.4N, 37.5W, heading W at 8mph. I think he's actually around the same intensity as Florence and I would place him as a very strong TS/borderline cat 1 hurricane at the moment. His forecast track is currently westward:

The good news is that he is about to head into an area of very dry and dusty air - the Saharan Air Layer (the orange area in the image below) - which will keep him in check: 

Although the official forecast says he'll be a hurricane in a couple of days, I'm not sure he's going to survive the crossing across the Atlantic if that forecast track holds true. This is really an interesting case because we'll see how much of an influence the Saharan Air Layer has on a storm (says the science nerd voice in me ;-)). 

Ok, time for another Lychee Martini... so much to talk about! 

TS Helene

Officially Helene is a mid-sized TS with winds of 60mph, central pressure estimated to be 999mb. She's at 13.2N, 22.8W, heading W at 13mph. I really disagree with the estimate on her intensity - I think she's clearly a cat 1 hurricane, possibly a border-line cat 2 storm actually. You can see from the satellite imagery that her convection is pretty robust. She also has the best 'outflow' of the three - meaning the cloud formation around the central strong convection is very good. But above all of that, she actually has a robust circulation (vorticity) at all levels of the troposphere. However, because we don't have data from inside the storm itself, the satellite-derived wind estimates place her as a mid-size TS. Sigh. This is one of the area's that we (at XPRIZE) are currently designing a prize around... if you can't afford planes and the storms are far from the coast, but that is the best data and really improves the forecasts, how do you get data from inside any storm, anywhere in the world?

Her forecast track is: 

Currently she's bothering the Cabo Verde Islands with some rain and a 'bit of a breeze'!

Ok, better run... apparently they won't hold the plane for my updates! ;-)

Toodle pip!

J.

Twitter: jyovianstorm

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DISCLAIMER:
These remarks are just what I think/see regarding tropical storms. If you are making an evacuation decision, please heed your local emergency management and the National Hurricane Center's official forecast. This is not an official forecast.
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TS Florence, TD Nine, TS Helene: September 7, Update A

Brevity with a touch of ludicrous whimsy in today's episode of 'The Constellation of Storms'.

They've added a yellow crayon to the collection for a bit of variety:

But they are currently all fairly weak. 

TS Florence is a little weaker than yesterday, with winds of 60mph, central pressure of 999mb. She's currently at 24.8N, 53.2W, and she's heading W at a slower 7mph (as she moves around that high pressure ridge I mentioned a few days ago). She's in a spot of wind shear, so she'll remain a little on the weak side for a day or so at least. If she escapes intact, then she may get stronger again. 

TD Nine: Officially he's not quite a TS yet with winds of 35mph (TS range: 39-73 mph). From his circulation (vorticity), I would say he is actually already at TS though, so I expect we'll be seeing TS Isaac tomorrow. 

TS Helene: You know, I know someone called Helene. Super lovely person, very fun, quite harmless, and loves to travel and dance... just like TS Helene, who just barely made it out of Africa and is already dancing and twirling away as she travels across the vast Atlantic! Hopefully this TS Helene will be like her namesake - harmless! :-) She's only just a TS with winds of 40mph, central pressure at 1002mb. She's at 13.6N, 18.5W, heading W at 12 mph. 

I'm traveling tomorrow (so I may not be able to post - we'll see) - everyone better behave themselves! But on my travels, I will be looking out for these gentlemen and lady... 

Toodle pip!

J.

Twitter: jyovianstorm

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DISCLAIMER:
These remarks are just what I think/see regarding tropical storms. If you are making an evacuation decision, please heed your local emergency management and the National Hurricane Center's official forecast. This is not an official forecast.
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TS Florence, the Atlantic Blobette, and the Atlantic Blob: September 6, Update A

I see that there was a sale on red crayons today and someone went a bit wild... 

It looks like we're in for a busy September. So, for your sanity and for the benefit of my lychee martini, I'll keep today's update pleasantly short.

That wind shear took a swipe at Florence and she's now a strong Tropical Storm again, with winds of 70mph (TS range: 39-73mph), central pressure 993mb. She's at 25.1N, 49.8W, heading WNW at 7mph. I'd agree she's a TS again - there isn't any circulation in the upper troposphere.  Although the track looks like it'll take her around Bermuda. Although it looks like she's heading to the US East Coast, it is far far too soon to say, and the chances are higher that she will recurve and stay away! 

Following Florence is the Atlantic Blobette... the future TS Helene. And now behind her, is an brand new Atlantic Blob... possibly the future TS Isaac. 

And that's it for today folks! Told you it would be short but don't worry, there'll be plenty more gobbledegook from me soon enough. ;-) 

Ciao,

J. 

Twitter: jyovianstorm

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DISCLAIMER:
These remarks are just what I think/see regarding tropical storms. If you are making an evacuation decision, please heed your local emergency management and the National Hurricane Center's official forecast. This is not an official forecast.
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Hurricane Florence and the Atlantic Blobette: September 5, Update A

A busy week this day ;-) so I'll be quick... 

Hurricane Florence

Well she not only went on the magic roundabout, but she's also had a go on the swings and slides since yesterday. She was, momentarily, a cat 4 storm, but she's now down to a strong cat 3 storm with winds of 125mph (cat 3 range: 111-129mph), central pressure 956mb. Florence is a good looking storm and has really good vorticity (circulation) in all levels of the troposphere, plus she has had a very clear eye and outflow during the day today:

 Although the wind shear did nothing to stop her from getting stronger earlier today, you'll notice from the satellite imagery that in the last couple of hours that she is really beginning to feel it and, in addition to the convection being mostly to the north and east of the eye, the eye itself is not as well developed. From this, I think she's probably now a weak cat 3 or strong cat 2 storm. 

She is still on track for the general Bermuda direction, but it's still too soon to say for sure if she'll visit for a round of golf or she'll do something else: 

She is currently at 23.4N, 47.2W, heading NW at 10mph. 

Atlantic Blobette

This one is somewhere around 12N, 30W, heading generally WNW. The circulation is slowly developing in the lower half of the troposphere, but isn't quite there yet. There's some convection in this system, so if the circulation continue to improve, this will be our TS Helene in a day or so. 

Finally... Happy 50th Wedding Anniversary to my Mum & Dad! :-) :-) 

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. If you are making an evacuation decision, please heed your local emergency management and the National Hurricane Center's official forecast. This is not an official forecast.
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Tropical Storm Gordon, Hurricane Florence, and the Atlantic Blobette: September 4, Update B

Goodness me, there's a bunch going on isn't there? Tropical Storm Gordon, Hurricane Florence, and another Atlantic Blobette! Better get an extra big glass of wine tonight!

Tropical Storm Gordon

He just made landfall in Mississippi, just west of the Alabama border about 30 miles east of Biloxi, at 30.4N, 88.4W. He is heading NW at 14mph: 

He's still a very strong tropical storm with winds of 70mph (TS range: 39-73mph), central pressure 997mb and didn't quite get to that cat 1 level. There isn't much circulation in the upper levels of the troposphere, so I agree with this. 

As I said earlier, he will really be a water issue more than a wind issue. He's got a bunch of convection which has been mostly falling over Alabama and half a bucket on the western end of the Florida panhandle during the day, and is now, of course, reaching Mississippi: 

Just make sure you have your umbrellas and raincoats handy! And stay safe out there. This is, most likely, my last update on Gordon.

Hurricane Florence

A memory from my childhood: Florence from the Magic Roundabout :-) 

(Photo credit: from the Main Characters of the Magic Roundabout)

(no, you don't need to clean your glasses... that's about the resolution of TV images back in those days :-)). 

She's currently out there in the Atlantic at 20.7N, 43.9W and is heading WNW at 12mph... with a big wide Atlantic to play in, of course she would be heading in the general direction of the only island out there, Bermuda: 

That track is a little too smooth at the moment - from the pressure fields, it looks like she'll continue more-or-less in heading WNW for the next day or two, but there's a good possibility that she'll then either slow down or take a turn to the west because there is a ridge of high pressure that she'll have to get around. It's a little too soon to say if she'll get to Bermuda island or jump on the magic roundabout and head back towards Europe, but best get the rum ready just in case. 

She's a mid-sized cat 2 storm at the moment with winds of 100mph (cat 2 range: 95-110mph), central pressure of 976mb. I'd agree with this estimate. She is definitely a hurricane because there is good circulation (vorticity) throughout the troposphere, including at the highest level (200mb): 

You can see a little 'green' splodge (technical term ;-)) peeking out under the solid red hurricane symbol, compared to Gordon (the tropical storm symbol), which doesn't have a splodge, but instead is teetering on the edge of an upper level low. If you need a refresher on the circulation and what the image above is showing, read the <Science Alert!> in this post: http://jyotikastorms.blogspot.com/2018/08/hurricane-lane-central-pacific-special.html.

You can also see her lovely circulation in the satellite imagery: 

The good news is that she is entering an area of stronger wind shear which will inhibit her from intensifying much more: 

(if you need a refresher on the wind shear map, check out the <Technical Alert!> here: http://jyotikastorms.blogspot.com/2018/08/hurricane-lane-central-pacific-special_24.html).

More on Florence tomorrow.

Atlantic Blobette

There's also a wee little blobette hanging out at around 12N, 24W, as you can see from the orange crayon mark on the image below:

There isn't much well-developed circulation at the moment, although there is some. There is also a little bit of rain and the NHC are giving her a 40% chance of developing into something fun in the next 2 days. The next name up is Helene!

And before I leave, a geeky tribute to Jaqueline Pearce, perhaps better known as Servalan, in Blake's 7 (my favourite TV show of all time), passed away yesterday. Supreme Commander Servalan is, hands down, the most fashionably iconic evil character in science fiction:

Paraphrased from the Guardian: She was no stereotypical evildoer with her "propensity to stride across the universe in glamorous attire...". She was clearly an inspiration to a generation of young ladies (such as myself!). (Just watch out if you see me in a black feathery top... bwaahaahaa ;-)). RIP and thank you! 

Until tomorrow,

J.  

Twitter: jyovianstorm

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DISCLAIMER:
These remarks are just what I think/see regarding tropical storms. If you are making an evacuation decision, please heed your local emergency management and the National Hurricane Center's official forecast. This is not an official forecast.
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Tropical Storm Gordon: September 4, Update A

Why is it that every time I travel to the wondrous Planet DragonCon (where my movie had its World Premiere! Hashtag trailer: https://vimeo.com/231982386), Mother Nature sneaks in a storm or TWO?!? This is a quick check on Gordon who is going to be touring the northern Gulf of Mexico coast later today. I'll look at the Hurricane Lady Florence later. 

Tropical Storm Gordon, currently at 28.5N, 86.8W is heading NW at 15mph. His track looks like he'll be making landfall somewhere close to the Gulfport/Bay St. Louis area in Mississippi: 

I would agree with the NHC on the track. 

Regarding his intensity, he is currently a mid-to-strong Tropical Storm with winds of 65mph (TS range: 39-73 mph) with a central pressure of 1001mb. He has some wind shear, so almost all the strong convection is to the east of the storm:

This means that although landfall will be on the western side of Mississippi, the rain and any thundery sort of weather will mostly be to the east of that - including Alabama and a bit of the Florida panhandle. 

Interestingly, his central pressure is quite high at 1001mb, so although the official forecast is that he will become a very weak cat 1 hurricane later today... that's because they don't think that the wind shear will be strong enough to keep him in check. It doesn't look like there's too much going on in the ocean that will cause a him to grow, so it is down to the wind shear. Alas, the latest wind shear data is not available at the moment, but if he does grow stronger it won't be by very much at all and he will really be a borderline Tropical Storm/cat 1.

Gordon will mostly bring water issues (with some wind impacts of course) - in addition to the convection on the east side, he is also going to be pushing water on-shore on the east side. Currently, it looks like water levels in places along the north-eastern Gulf are around 1ft above normal. If you want to look up the storm surge for yourself in the area closest to you, read the <Technical Alert!&gt in this post which discusses NOAA's replacement storm surge site tidesandcurrents (https://tidesandcurrents.noaa.gov/).

Stay safe out there my peeps! I'll be back later with an update on Gordon & Florence. 

Ciao for now,

J. 

Twitter: jyovianstorm

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DISCLAIMER:
These remarks are just what I think/see regarding tropical storms. If you are making an evacuation decision, please heed your local emergency management and the National Hurricane Center's official forecast. This is not an official forecast.
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Tropical Storm Lane - a Central Pacific special: August 24, Update A

Aloha out there! Hurricane Lane is now Tropical Storm Lane! Hurray! 

That wind shear definitely took its toll and his winds are now 70mph (TS range: 39-73mph), central pressure is 985mb. Although he's only just below a cat 1, he's clearly in a much nicer category for all concerned and for those beautiful islands:

It looks like he's just about started to make the turn from heading almost due north, to now heading NW, although his speed is a very slow 3mph. His forecast continues to show him turning and heading west: 

But despite this weakening storm and the turn to the west, the islands are still going to get a bit more rainy weather because he's still got some circulation in the lower half of the troposphere, and there's still some convection, which is being swept to the northeast (and over the islands) because of the wind shear:

He'll continue to sputter on for a few days, but he'll remain in that area of strong wind shear, so I don't think he'll be bouncing back. I'll keep an eye on him in case something wonky (technical term! ;-)) happens, but for now I think it looks like this will be my last post on Lane! 

Next up in the eastern/central Pacific would be Miriam, and next in the Atlantic will be Florence. 

Wine pairing for today's version of Lane. I'm thinking definitely lighter-bodied but still fruity - a Pinot Noir perhaps. :-) (you know, one of these days I'm going to get my storms and wines all confused and then I'll be talking about Hurricane Merlot or Tropical Storm Barbera). 

Stay safe out there!

Ciao for now,

J. 

Twitter: jyovianstorm

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DISCLAIMER:
These remarks are just what I think/see regarding tropical storms. If you are making an evacuation decision, please heed your local emergency management and the National Hurricane Center's official forecast. This is not an official forecast.
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Hurricane Lane - a Central Pacific special: August 23, Update A

Well things are looking brighter today than they were yesterday - unless you are on a few of the Hawaiian islands, in which case things are looking cloudier and rainier today than yesterday. But it's looking generically-speaking brighter for you too!

Hurricane Lane did actually get steadily weaker throughout the day today and is officially now a mid-size cat 3 storm with estimated winds of 120mph (cat 3 range: 111mph - 130mph), central pressure 959mb. And it's great - we can very clearly see the impact that the wind shear is having on him in the satellite imagery:

He's gone from that symmetrical circular shape to an egg shape (technical term ;-)) and the outer band clouds (blue) are streaming off to the north and east. (By the way, if you're looking for Hawaii - it's under all that cloud cover (blue) and rain (yellow)):

There is still a LOT of strong convection and thunderstormy weather in him though - that large area of red in the above infrared images indicates that. He does still have an eye, which is easier a little easier see in the visible imagery (although the light is fading towards the end):

And really great circulation (vorticity) in all layers of the troposphere, so he is definitely at hurricane strength, but with that wind shear being so strong, I think he will continue to weaken.

<Technical Alert!> If you want to see the vorticity (as I mentioned a couple of days ago) and the wind shear, the best place to look is the University of Wisconsin-Madison's CMISS site: http://tropic.ssec.wisc.edu/tropic.php. Scroll down to the lower map and over the box that covers the area that you are interested in. In this case, the Northeast Pacific. From the drop-down menu you get if you hover your mouse over that area, pick the top one - Winds & Analyses. At the top you will see a bar. Pick 'Wind Shear' and you should see something like this:

Find Hawaii (no, this is not a drinking game!). Just to the south and under all the squiggly lines, you'll see Hurricane Lane as the mass of gray clouds (this is like that picture where everything becomes clear if you squint and turn your head just right ;-)). You'll see it is mostly under some pink lines and some red lines (having moved through the green and yellow lines earlier in the week). The pink lines are the wind shear - the closer they are, the stronger the shear. The red lines are contours and have numbers on them - this indicates the amount of wind shear in that area. And if you haven't squinted too much, you'll notice little arrows on the pink lines - this is the direction of wind shear. 

For vorticity, got back to the bar at the top and you'll see '850mb Vorticity' (for the lowest level of the troposphere), '500mb Vorticity' for the mid-troposphere, and '200mb Vorticity' for the highest level of the troposphere. Here's the vorticity map from 850mb:

Although there is clearly a signal, it's not as round and detached as it was before. Another clear sign that he's weakening. <End Technical Alert!>

He's forecast to be cat 2 storm in 24 hours - and I think he may even drop down to a cat 1. 

He is centered at 17.8N, 157.9W, and is heading almost due north (NNW) at 6pm. 

They think that the track will stay to the south of the islands - this is because he has been staying consistently to the west of the center of that cone. There is a turn expected, as you can see. The reason why the cone is so large is because they don't know quite where the turn will take place - it could get closer to the islands in which case the weather will be worse. I will go with the track forecast as I don't have any data over the Pacific that would be helpful. 

Wine paring for this storm today... he's a little mellower, but still full of flavor. Hmm. Maybe a Chenin Blanc? 

Stay safe in Hawaii my friends. It'll still be rainy and windy and rainy some more! 

Aloha!

J.

Twitter: jyovianstorm

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DISCLAIMER:
These remarks are just what I think/see regarding tropical storms. If you are making an evacuation decision, please heed your local emergency management and the National Hurricane Center's official forecast. This is not an official forecast.
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Hurricane Lane - a Central Pacific special: August 22, Update A

Aloha! The story so far... another beautiful day on Oahu today...

(photo credit: Malia M.)

Meanwhile, off in the distant south, Hurricane Lane is still a pretty good looking, decent cat 4 storm with winds estimated from satellites to be 145mph, central pressure of 939mb (cat 4 range: 131 - 156mph). Given his vorticity structure (which you know all about now - if you don't read yesterday's post! :-)) throughout the troposphere and his current satellite appearance, I think he's a little stronger than this, but there are factors that are coming into play that will hopefully weaken him a little over the next couple of days. 

He is currently at 15.9N, 156.5W and about 260 miles south of the Big Island, so he still has a way to go to get there. He's moving NW at a slightly slow 8mph:

The good news (so far) is that he has been moving a little more to the west of the center of the cone so the forecast is that he won't be a direct hit on the Big Island, however they will still get some strong winds and they are already collecting a few bucket-loads of rain. In addition to the rain, storm surge will be high on the south and west coasts because winds move in a counter-clockwise direction around a low pressure system (which is what a hurricane is), so as he passes by to the west, he'll also be pushing water on shore. 

Because he isn't going to be as close to this island, it won't have as big an influence on reducing his intensity as it looked like with yesterday's track. However, the wind shear is still in place and the main convective area should start to interact with that in the next 24 hours - by tomorrow we should see begin to see some of the effects of that in the clouds on the satellite image. For today, he is still looking good:

You can see some of the wind shear taking hold of his outer rain bands - the clouds that are streaming off to the north and then being carried away to the east. 

Tomorrow I think we should begin to see a gradual weakening but I think he'll still be a cat 4 tomorrow, despite the wind shear. One thing that will sustain him is that the ocean is quite warm, and he's about to move into an area where the upper ~100m of water is warmer than 26 deg C - which means he has enough fuel to sustain him. The competing influences of the ocean and atmosphere will only very slowly decrease his intensity.  

And now for a new feature (thanks to Aida A. for the suggestion)... a wine-paring to go with this post. Hmm... Lane is a full bodied, robust storm that is being a bit of a nuisance to some very nice islands, so I am not a huge fan of him... I think that'll be a Shiraz! ;-) 

Until tomorrow!

J. 

Twitter: jyovianstorm

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DISCLAIMER:
These remarks are just what I think/see regarding tropical storms. If you are making an evacuation decision, please heed your local emergency management and the National Hurricane Center's official forecast. This is not an official forecast.
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Hurricane Lane - a Central Pacific special: August 21, Update A

Eesh. Mr. Hurricane Lane! Well the good news for today is that my on-the-ground reporter, Malia M., said this morning that the surf was pretty good on the north shore of Oahu and it was a lovely beach day today. 

But we can see that Lane is slowly creeping towards the islands. He is currently at 14.5N, 154W, and has started that curve to the north. He is heading WNW at 9mph. The overall track has shifted to slightly to the north, but there is still a large range of uncertainty so keep in mind that he could go anywhere in that cone: 

Unfortunately, he did get stronger during the day and is now a cat 4 storm  with winds of 160mph (cat 5 range: >156mph). The data is extracted from hurricane hunter planes, but his satellite imagery also supports a robust storm. We can see a really good, solid, clear eye that has been in place all day. The infrared imagery also shows a very large band of very strong thunderstorms around the eye (the red part):  

The water vapor imagery shows the overall cloud structure more clearly and we can see a good outflow (that curved 'sawtooth' pattern) on the west and north side of the storm, which is another sign of a well developed storm: 

The final clue that he is a solid storm is his vorticity (circulation), which is is also very well strong in all levels of the troposphere. I think it's almost time for an exciting <Science Alert!> on Vorticity, but before I jump into that, a few more observations on Lane and Hawaii. 

Although the track is looking a little dodgy for the Hawaiian islands and he is the strongest storms that has passed this close to Hawaii for decades, there are a few things that may reduce his intensity before he gets close to Oahu (at least):

1. There is still some wind shear between him and the Big Island. It's may keep him slightly in check, although he is strong so it won't be as big an influence as it would be on a smaller storm, but it will be something.

2. He will interact with the Big Island of Hawaii, which has mountainous terrain, which will keep him in check and may reduce his intensity as well. The outer bands have already started to cover this island, with some light rain on the southern and eastern shores:

This poor island! I can see the movie titles: Battle of The Natural Disasters! Or stay tuned for Lane versus the Volcano!

3. As he interacts with the other islands before getting to Oahu, his intensity will also be kept in check and maybe reduced. The extent of how big an impact this will have depends on how close his center gets to the other islands. 

4. Finally, his track may keep him to the south of the islands entirely - that cone is still very wide. 

If you are on the islands, remember:

1.  Run from the water, hide from the winds. This means that if you are in a place that will flood, move inland. If you are in a place that won't flood, hunker down. The greatest loss of life in a storm is from water - storm surge, flooding from rain and rivers etc. 

2. Be careful after the storm - downed power lines and water don't work well together so be careful where you walk. 

3. Get supplies for a few days (more than 3) - if you are in a place where the roads are small, they may be impassable from debris. If the power is out, then you may be stranded for a few days until help arrives. (Get some ice cream in too - if the power goes, you'll have to eat it first and it will keep you cool as well. That's my solution to many things. :-))

4. Listen to your local emergency managers - they have the best information for your locale!

Ok, now for a fun bit-o-science! Are you ready? :-) 

<Science Alert!> Vorticity: 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. Well, 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, 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 cylones, 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). <End Science Alert!>

So lets look at the Pacific and Hurricane Lane. Here is the vorticity map for 850 mb (the lowest level of the troposphere): 

You can see the signal of Hurricane Lane just south of Hawaii - the big red splodge (technical term), conveniently covered by a hurricane symbol. 

Here's the map for 500mb (the middle level of the troposphere):

In this, you can still see a nice round, red splodge in the same place as the 850mb level map. You can also see another red splodge to the northwest... but this second one isn't a hurricane because there isn't any circulation in the lower level of the troposphere. It's just in the middle levels that there is some movement.  

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

In this upper level map, you still see a very nicely defined Hurricane Lane vorticity signal - still orange/red, which means that there is some good circulation throughout the troposphere - we only see a signal of vorticity in this upper level if a tropical storm is actually a hurricane. And the stronger it is up here, the stronger the hurricane. Meanwhile, that other red splodge doesn't have a corresponding signal this high up. But instead, we see a lot of lines - there is vorticity up here, but it is more like low pressure fronts (troughs). 

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! I'll talk about how you can access them for yourselves in a future post. 

I think that's it for now. Get ready and be prepared my friends in Hawaii! 

Aloha! 

J.

Twitter: jyovianstorm

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DISCLAIMER:
These remarks are just what I think/see regarding tropical storms. If you are making an evacuation decision, please heed your local emergency management and the National Hurricane Center's official forecast. This is not an official forecast.
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