Hurricane Milton: October 9th, Update A

With a few hours until landfall, a large region of the Florida peninsula is already feeling Tropical Storm force winds (TS range: 39-73mph) from Hurricane Milton, which extend over 200 miles from the center. Hurricane force winds are within 35 miles of the eye, and as he is about 50 miles off the coast, those winds have not yet reached the coastline. 

He is at 26.9N, 83.4W, heading NE at a very brisk 17 mph, which means he will be making landfall sometime around 9 or 10pm local time, north of Sarasota. He weakened during the day and was very asymmetrical because of the strong wind shear and also because there was dry air making it's way into the center of the storm, which caused him to weaken from that monstrous cat 5 to a cat 3. However, over the last couple of hours, the wind shear has weakened slightly and it looks like the convection has reformed around a center, so the dry air is no longer making it into the center of the storm. Officially, he is a mid-size cat 3 storm with winds of 120mph (cat 3 range: 111 - 130mph), central pressure of 948mb. 

There is a lot of very strong convection, which brings with it tornadoes as well as substantial thunderstorms. You can see these areas as the orange/red/black regions in the infrared satellite imagery:

Landfall looks like it will be somewhere north of Sarasota, but it is difficult to see where exactly relative to Tampa Bay:

Storm surge is only about 0.75 ft above normal in areas around Tampa Bay at the moment, but it is about 3 ft above normal in Fort Myers. This is because the storm is still south of Tampa - if it makes landfall to the south, the storm surge will not be too high. If it makes landfall to the north or in the Bay, then water levels will most likely rise. Surprisingly, there are no storm surge measurements available on NOAA's Tides and Currents website (https://tidesandcurrents.noaa.gov/map/index.html) between Ft. Myers and Tampa Bay, so we don't know what the levels are in Sarasota.

Be safe!

Toodle pip,

J.

Twitter (now a 'placeholder letter') @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.

Hurricane Milton: October 8th, Update A

This is a post in three acts: (i) a Milton update, (ii) for those who evacuated in Florida, and, (iii) for those who have hunkered down in Florida. At this point, it is almost too late to decide to evacuate because you don't want to be on the road as the weather deteriorates ahead of the storm. However, if you are in an area which is prone to flooding, please run away to higher ground (like Brave Sir Robin, Monty Python). 

(i) Milton Update: Milton is back up to being a cat 5 storm with winds of 165mph and central pressure of 918mb. He did weaken a little as he scrapped the northern edge of the Yucatan Peninsula, dropping to a cat 4 storm, but he has just officially stepped back up to cat 5 status. He is at 22.7N, 87.5W, heading ENE at 9mph and is a very robust and good looking storm:

Intensity: I mentioned yesterday the battle between the atmosphere and ocean. You can see the effects of some of that in the Infrared satellite image above. To the northeast of Milton, there is outer band which has very strong convection (which is marked by the red and black regions) - this is an area with thunder, lightening, very heavy rainfall etc. The region that outer band is going over is an area in the Gulf of Mexico which has very deep warm water - the upper 125-150m is warmer than 26 deg C. This is part of the Loop Current, which fluctuates in the northern extent it reaches into the Gulf.  So... the bad news is that Milton still hasn't got to that warm water yet - I estimate at the speed he is moving, it will take about 6-12 hours. This will allow him to grow and intensify. 

But the wind shear in the atmosphere is doing it's best to inhibit his intensification - and you can also see that in this satellite image as the clouds stream off to the northeast. 

Unfortunately, there is one more thing at play here which is also allowing him to intensify, and that is that he is not only getting his energy from the warm water, but also he is starting to get some from the atmosphere, and we can see this in the circulation in the lower levels of the atmosphere.

Given that his winds are already 165mph, the wind shear may not have too much of an impact and he may be making landfall as a cat 4 storm. 

Track: A precise location is really tricky because Milton is moving between a larger low and high pressure, both of which are also fluctuating. The NHC said today that at 36 hours away from landfall, their track can be off by an average of ~60 nautical miles/~70 miles (1 n mi = 1.15 miles). Although the forecast track has shifted slightly to the south, that is because the models have caught up with the slightly more southerly track that Milton has taken. I do expect him to begin to head slightly more north in the next few hours, moving from the current ENE to a NE path. It will be close to Tampa Bay - and it will make a difference if it makes landfall to the south or the north. If it is to the north, more water will be pushed into the bay and storm surge will be much higher. Landfall can still be anywhere in the cone: 

In case power goes out tomorrow, I'm adding a few more bits and pieces... the biggest thing is to heed your local emergency managers - they know what's what in your local area. 

(ii) For those who evacuated: If you moved inland and are still in the cone, the storm will still be a hurricane as it passes overhead. You may lose power and amenities. Also, you may not be able to return home for a week or two (or more depending on if it is a cat 5) - until roads have been cleared, power restored etc. 

(iii) For those who hunkered down in the area of landfall: Things to be prepared for - in addition to perhaps not having power and amenities for a few weeks. During the storm, in addition to the wind, thunder, lightening, and rain, there are tornadoes - have an interior room or closet you can shelter in with supplies if there is a tornado - something away from windows. After the storm passes (or during the calm eye), be careful if you go out because there may be downed power lines in water. Cell phones may not be working for a week or more. It can be very tough in the weeks after a storm. 

I know many who have evacuated, and many who are staying. Wherever you are, please be safe!

Toodle pip, 

J. 

Twitter (now a 'placeholder letter') @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.

Hurricane Milton: October 7th, Special Update

Dear Friends,

Well I certainly picked the wrong year to 'retire' from my hurricane blog! Oh. My. Goodness. Apparently Mother Nature was not happy about this early retirement malarky, was she? 

To those who reached out to ask about Milton... umm... it's definitely looking dodgy out there! As you know, Milton is currently at 21.8 N, 90.8 W and is moving E at 10mph. He has grown to a very strong cat 5 storm - winds are 180mph (cat 5 storm range: greater than 156 mph) and central pressure is a very low 905 mb! I would agree with this intensity - the eye is very clear, steady, and strong and has been for hours:

And the track forecast has been pretty consistent - following the flooding from Helene, this is going to be messy at any level:

Before I go into the data, here are some practical snippets and tidbits:

- Listen to your local emergency managers - they know the area you are in. Please evacuate if they tell you to. 

- Run from the water, hide from the wind. Meaning - if you live along the coast, or in an area prone to flooding, please evacuate. 

- I would also evacuate  if you are in a region experiencing a major storm - meaning if it is cat 3 or higher. Currently, the forecast to be a cat 3 on landfall. 

- Given the trajectory of the storm, if you can evacuate to the north or to the very south of the Florida peninsula that would be best. If it makes landfall as a cat 3, it may be a cat 1 by the time it gets across the state, so the middle of the state may get cat 2 winds. If it makes landfall as a stronger storm, it will, of course be stronger as it crosses the state. Generally, it drops two categories in crossing the Florida peninsula (depending on how fast it is moving). 

- If you evacuate, and you are in a region which gets a direct hit, you may not be able to get back in for a couple of weeks or longer - depending on flooding, debris, and power. 

- If you decide to evacuate, get out early. 

Now for what's happening out there.

Although he is currently a strong cat 5 storm, he is approaching the Yucatan peninsula, which will decrease his intensity slightly. He also has ahead of him a bit of a battle between the ocean and atmosphere. He will be passing over some deep warm water tomorrow (thanks to the loop current), which means he has a source of energy. However, there is also some very strong wind shear - you can already see this in the satellite imagery as the clouds are streaming off to the northeast. It looks like this wind shear may get stronger, so he will decrease in intensity, but given how strong a cat 5 he is now, he may still be a cat 4 on landfall. 

As for his track, although the center of the cone is on Tampa Bay at the moment, please keep in mind the entire cone is still a possibility for landfall. 

This is almost the strongest storm I've seen in the Gulf of Mexico - the last one was when I started the precursor updates to this blog in 2005, and that was Hurricane Wilma, which reached 185mph wind speed.

I know many of you who are evacuating, so good luck to those who are leaving, and to those who are not. I will post again tomorrow! Stay safe! 

Toodle pip!

J.

Twitter (now a 'placeholder letter') @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.

Hurricanes Lee and Margot: September 13th, Update A

Hurricane SlowLEE (teehee) is finally approaching land, so I thought I better pop in and say a few words. And also, we have just crossed the statistical mid-way mark of the hurricane season (Sept 10th)... 

Wo-oah, we're halfway there, wo-oah... 

(and if you are like me, you will never sing the original lyrics to that song again! :-)).

Lee been a been moving at a bit of a sedate pace as storms go - he was named on the 5th of Sept, and looked a bit ferocious on the 7th when he was officially and briefly a cat 5 hurricane,  but dropped down cat 4 on the 8th and he's been weakening since then, so he is now a cat 2 storm with winds of 105mph (cat 2 range: 96-110mph), central pressure of 953mb. He's not as robust looking as he was earlier in his life:

There is still some convection (rain and thundery weather) but it's not as evenly spread as one would see in a hurricane, but he does clearly have an eye and his circulation is throughout the troposphere so he is definitely a hurricane. He is expected to decrease in intensity and there are many reasons to think this will be the case. First, there is some wind shear ahead of him - you can see the clouds to the north streaming off into the yonder distance. Second, he is also about to move over cooler sea surface waters of around 26 deg C, with only the upper 25-50m of water at that temperature. And third, the air to his north and west is dry. 

His outer bands are already over Bermuda - mostly just cloud and rain - and tomorrow will be a bit breezy, but it should be quite nice by the weekend. Perfect for golf and sailing if you are in Bermuda, but maybe not advisable as 'fun activities' in Maine and Newfoundland this weekend... he's currently at 28.0N, 67.7W heading N at 9mph...

He should be a Tropical Storm by the time he gets to Canada - but a strong storm so get ready up there! There is a front moving across the eastern US which will meet with Lee. The double impact of this is that (a) it is why he will curve to the east and (b) it will add some energy, so although he may not have too much rainy and thundery weather by Saturday evening, he will be a blustery. 

I'll keep an eye on Lee in case he does anything funny in which case I'll pop back, but the NHC forecast seems about right. For those who are in the path, remember to listen to your emergency managers!

Now, there is another hurricane out there... Hurricane Margot. She's at 35.2N, 40.5W heading N at an even slower 7 mph. Winds are 85mph which makes her a cat 1 storm (cat 1 range: 74-95mph), central pressure is 972mb. However, she is a bit confused and going round in circles...

So, of course, I won't be saying too much more about her either.

Be careful and Toodle pip for now! 

J. 

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

Twitter (now a 'placeholder letter') @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.

Hurricanes Franklin and Idalia: August 29, Update A

Busy day today all over the place! Well, maybe not in Florida, but everywhere else I'm sure. ;-) Ok ok, I know you have been very busy over yonder, preparing today, boarding up, and getting supplies so you are well stocked up (or have evacuated)... but hands up, who's also been doing this...

(Image Credit: unknown from the internet, but The Simpsons are great!)

Hurricane Idalia 

She is currently at 27.4N, 84.6 W heading N at a very fast 18mph. She is on track to make landfall in the Florida Big Bend area tomorrow morning at around 8 or 9am.

She is tracking slightly west of the official center but still towards Apalachee Bay (luckily not a very populated area, except by wildlife) and within that cone. Although the track shows that she will cross S. Carolina and southern N. Carolina and enter the Atlantic, that far end is because I think the models are picking up Franklin... however, as Franklin will be moving northwards, I think that track may straighten out a bit so she may be over N. Carolina a little more than is currently shown - she may cross some of the outer banks before heading into the Atlantic. 

For those of you on the east side of the storm in Florida, you will experience storm surge as I mentioned yesterday - and there's a SuperMoon tomorrow, which means that your normal High Tide will be higher than normal as well! ever wondered how you can find out the storm surge in your area? Well, today's your lucky day... 

<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 waves of recent times 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 general locations of the stations monitoring the water levels along the coast. You can either locate the nearest station by entering the area you are interested in, or click on the station nearest to the location of interest, which will zoom into the map. So by clicking on the icon over Tampa Bay (which has the number 17), the stations along the south west coast of Florida come into focus. 

Now clicking on the specific station of interest, 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). Just watch out 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 then will have to zoom out until the map you want re-appears and then zoom back in.

Here is the plot from Ft. Myers for example:

You can see that the actual water level in red has been higher than the predicted levels since yesterday and that gap is widening as the storm is passing by offshore. 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 water levels currently about 1.5-2 ft above normal. 

Moving a little father up the coast to St. Petersburg, the water level is also about 2ft above normal

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 is decreasing as the storm gets closer.

And the winds: 

which are given in knots (1 knot = 1.15 mph) which means the winds here are approaching 20mph. 
<End Technical Alert!> 

She is definitely a hurricane. In addition to having strong circulation at all levels of the troposphere, she has a good looking eye now:

But clearly the rain bands are already over the peninsula and reaching Georgia. Winds are 110mph, central pressure 960mb, which makes her a strong cat 2 storm/borderline cat 3 (Cat 2 range: 96-110mph).

As for her intensity over the next few hours - there are glimmers that she may not grow into the very strong cat 3 (125mph is the forecast!) that is currently forecast (although she will definitely be a hurricane at landfall) because:

1. it does look like the wind shear is increasing in front of her so hopefully that will at least stop her from growing - and we can see that because the bands are streaming off to the northeast. 

2. the dry air to her west is also inhibiting her a little - we can see that from the ragged looking outer bands to the west side and the drier part to the south.

3. she is now moving over water where only the upper 50m or so is warmer than 26 deg... although she is moving quickly, so she may not churn up as much cooler water as one would hope so this may not be as big of an effect. 

Stay safe out there! Don't jump around in puddles after the storm has gone until you are sure there are no downed power lines. Good luck! 

 

Hurricane Franklin

Meanwhile, in the Atlantic, not too much has changed. Franklin is still a major cat 3 hurricane with winds of 125mph, central pressure 947 mb (cat 3 range: 111 - 129mph). He is at 31.9N, 69.4W, heading NE at 12mph: 

And my, what a big eye he has! You could fit 10 Bermuda's into that eye! 

Although he looks huge, his convection isn't as bad as it could be and he is going to pass by Bermuda tomorrow with only the outer bands passing overhead. I do believe surf's up there - and along the US Eastern Seaboard!

That's all for today. I know there's another blobette out there (Tropical Depression 11) but I'm ignoring her for now.

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.

Hurricane Franklin and Tropical Storm Idalia: August 28, Update A

I'll sum up some wrap-up thoughts from last week on the US west coast some other day. Today, it's once more unto the breach dear friends, and over to the Atlantic and Gulf of Mexico where the game's afoot. Are your supplies ready? Water? Candles? Ice Cream? Wine?

Tropical Storm Idalia

She is getting stronger as I'm sure everyone in Florida and the southeastern US are already aware... 

She's currently at 22.0N, 85.0W, heading N at a stately 8 mph. Her track is bringing her into Florida, but the center could be anywhere in that cone so don't focus on the center of it. We are still over 1.5 days away and that could shift slightly.

One of the big issues is going to be storm surge along that coast of Florida and the amount of surge depends on the track, but also on a number of other things.

<Science Alert!> Storm surge is water rising along the coastline as a storm approaches and makes landfall. How high the storm surge is depends on a number of factors: 

1. Location at Landfall. Storms are low pressure systems, so in the northern hemisphere they rotate in an anticlockwise direction.  This means generally water will be pushed onshore on the right side of the eye (eastern or southern side depending on if the coast runs E-W or N-S) side of the eye, and will be pushed off shore on the left side (western or northern side depending on coast orientation). In this case, if Idalia makes landfall just to the north of Tampa Bay (for example), she will push water up into the bay and storm surge will be higher. 

2. Intensity. Storms are low pressure systems, which means that there is low atmospheric pressure in the middle. But obviously we don't have a low pressure "hole" between the air and the ocean. Instead the water 'rises' up to fill the 'gap' which is created by the atmosphere's low pressure. So, the stronger the storm is, the lower the central pressure, the greater the 'gap' for the water to rise to 'fill' and therefore the higher the storm surge. 

3. Speed of the storm. If a storm is moving quickly, then there is simply less time for water to get pushed onshore before the storm has swung by. Storm surge is greater for slower storms. 

4. Angle of storm approach to land. Depending on if a storm is approaching land directly or at an angle can affect the amount of storm surge because of the direction of the winds. Storms that are heading directly onto shore result in greater storm surge than those that are approaching it from an angle - skirting along the coastline. 

5. Shape of coastline (bays etc). Water can get piled into bays and upstream in estuaries of course. 

6. The depth of the seafloor just off the coast is important. For areas with a shallow seafloor, more water piles up compared to areas where the seafloor is deep just off the coast. 

<End Science Alert!>

For those who need a reminder, I use NOAA's tidesandcurrents website. For those who haven't seen this before, I'll cover how to find out what you need to know in tomorrow's post. 

(https://tidesandcurrents.noaa.gov/) 

Idalia is currently a Tropical Storm with winds of 70mph, central pressure 983mb, which makes her a very strong Tropical Storm (TS range: 39 - 73mph)... actually, I think she is already a hurricane because her circulation (vorticity) is already present throughout the troposphere.  She just clipped Cuba but that wasn't enough to inhibit her development: 

She looks like she has a lot of convection - that's because she is moving over a part of the ocean which is very warm, with sea surface temperatures over 30 deg C. But not only is the surface hot, the upper 125 meters of ocean is warmer than 26 deg C - so anything she is churning up is definitley feeding her! Her blossoming like this in this part of the world is not unusual though, because she is going over the Loop Current System... yes, squeezing in another <Science Alert!>. :-)  

<Science and Forecasting Alert!> The Loop Current (System). The Loop Current is part of an ocean current system that flows from the Caribbean into the Gulf of Mexico through the Yucatan Strait, and then out of the Gulf of Mexico through the Straits of Florida, and up the east coast of the US. How far it extends into the Gulf of Mexico varies from year to year and month to month. As this current flows around Florida, it changes name to become the Florida Current. Then as it flows up the east coast, it changes name again and is known as the Gulf Stream. It leaves the US east coast around North Carolina and flows across the north Atlantic to the UK. Why is this current system important for tropical storms? This current system is well known because it has the deepest warm waters, and is very fast flowing - but the current also has offspring that can also have deep warm waters (all these offspring are called Eddy by the way). The deep warm waters mean that tropical storms that pass over any part of this current system or over any warm water Eddies have a jolly good (British understatement) chance of becoming stronger. 

So, how can you see where these areas are? One of the places I look is buried within the vast network of websites that NOAA has. In particular, the Office of Satellite and Product Operations has a site called Satellite Heat Content Suite (I know, such a catchy name - made for a song lyric I'm sure! ;-)). I use the North Atlantic page: 

https://www.ospo.noaa.gov/Products/ocean/ohc_natl.html

If you click on this, you will see all sorts of maps. The two most useful for our purposes is the one on the top left - Sea Surface Temperature - which looks like this today: 

You can see that the waters where Idalia is are the darkest of dark reds - over 30 deg C. The other most useful map (more so than the sea surface temperatures actually) is the depth of the 26 deg C Isotherm - third one down in the right column and that looks like this today:

From this, we can see that Idalia has been passing over that area of yellow/green just north of the western tip of Cuba - this is where the upper 125m of water is warmer than 26 deg C. No wonder she picked up some convection. <End Science and Forecasting Alert>

The current forecast is for a major hurricane at landfall on Wednesday. A major hurricane is a cat 3 or higher storm (111mph winds or higher). At the moment, I don't see anything that will inhibit her from growing in the next few hours - the water is toasty, and there isn't much wind shear around. There is a bit of dry air to her northwest, over the Gulf, but I'm not sure it's close enough to combat that convection. However, the 26 deg C depth does get shallower as she moves northwards, so there is a possibility that will help to keep her growth in check - but to decrease her intensity requires strong wind shear as well, so that's what I will look for tomorrow. 

Hurricane Franklin

Just a quick note on Franklin, who is in the Atlantic at 29.4N, 71.0W, heading N at 9mph. He is already a major cat 4 hurricane with winds of 150mph, central pressure of 926 mb (Cat 4 range: 130-156mph), but is going to avoid Bermuda and stay away from the eastern seaboard as well: 

He's a good looking chap (what else would you expect with a storm that strong?), but not a big fella... 

Bermuda will get some rain, a bit of a breeze, maybe not a golfing day on Wednesday, but hopefully nothing too bad. 

For those in Florida - get ready and listen to your emergency managers - they know the area the best. If you are in an area that floods easily (yes, I know we are talking about Flat Florida - hard not to get some flooding!), then please evacuate if you are told to. 

Until tomorrow!

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.

Hurricane Hilary (Pacific) and TD 6 (Atlantic): August 19, Update A

As I sit here, sipping my tea, in the skies overhead there are clouds circling and a helicopter circling. One of these is normal for LA. :-)

Hurricane Hilary is at 24.4N, 114.2W, heading NNW at a fast 17mph! They have moved the track forward in time, so if you were expecting her to pass by on Monday, that was yesterday's plan. Now her center will clip Baja tonight... 

Make landfall tomorrow afternoon (Sunday, 12pm = noon), and have zoomed by the LA region by midnight. This doesn't mean that the effects of the storm will be over by midnight on Sunday - those I expect will continue into Monday (you will see why below). 

She's decreased in intensity as we expected and is now a weak-mid level cat 2 storm with winds of 100mph (cat 2 range: 96-110mph), on target to hopefully be a weak cat 2 or strong cat 1 as she clips Baja. Her convection (and circulation) has really decreased quite a lot:

And if you look at the track and where the main convection is - you will see that it's mostly on the east side and south of the storm. This means that the bulk of the rainy sort of weather will be inland California - San Bernardino etc. - if it continues to have heavy convection by the time it reaches that far north.

But even as the center passes by, the storm isn't over because you can see that there is some heavy convection on the southern side of the storm as well - and if that persists, there will be also be a lot more 'weather' in the wake of the eye.

Although she hasn't even got half way up the Baja peninsula, because of wind shear, the clouds (some with rain) are already streaming over Southern California and north - even over Nevada, Oregon, Idaho, with the very outer edge reaching Canada:

That's quite a lot of rain - but I suspect it is needed. 

I was asked how I knew yesterday that the storm was weakening, even though the plane was flying to gather more data:

1. The cloud tops in the infrared satellite imagery were getting warmer (less of the deeper clouds indicated by the red areas compared to the day before).

2. I knew she was heading into an area with dry air to her north and west (as seen in the water vapour imagery - she was less 'circular' and a bit more ragged on her western side).

3. She was moving north and over cooler water - not just the sea surface, but the depth of water that was warmer than 26 deg C had also almost vanished, so anything she churned up to gain energy wasn't going to be enough to sustain her.

4. The wind shear had picked up - and we see that today as well because the clouds are streaming off to the north.

The one reason I thought she may take a while to get off that cat 3/4 ledge is because her circulation (vorticity - science!) was still strong throughout the troposphere (science!), which means she had still got some oomph (technical term ;-)) to her. 

And that brings me to a <Science Alert!>.  Woohoo! :-)

<Science Alert!> The troposphere. Our atmosphere is divided into layers – like a delicious trifle or seven-layer dip or lasagna (depending on what 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 (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 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. 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’). ;-) So, looking at the infrared imagery, it measures the tops of the cloud temperatures and so colder they are, the stronger the storm. 

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... and so we go on until we get to space...<End Science Alert!>

Some last minute notes:

- Please do heed your local emergency managers. 
- If you get a lot of rain and wind, and go out after it has passed, be very wary of downed power lines in water. 

- If you are in a flood zone, evacuate. If you are not in a flood zone, then find a place to shelter away from windows if the wind picks up. Water is the biggest cause of loss of life in Tropical Storms, not the wind. 

- Don't go surfing... although I know that's a silly thing to say to the surfers I know! :-) 

- Be safe, enjoy the ice cream!

That's it for the Pacific... in the Atlantic, I see they have Tropical Depression Six... it looks like it will fizzle out in the Atlantic, so I'm not going to bother. I'll keep an eye on the crayon artwork that Mother Nature has produced over there though just in case... 

Toodle pip until tomorrow!
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.

Hurricane Hilary: August 18, Update A

With Hurricane Hilary out there and still heading in this direction, I've started going through my hurricane checklist... two lychee martinis later, I'm now onto the ice cream which, may I say, is quite delicious. If you are a regular reader, you may be wondering where the wine went... me too! ;-)

Before we get to what else is on my checklist, what's going on with Hilary? As expected, she intensified to a mid-size cat 4 earlier today (winds got to 145mph - cat 4 range is 130-156), and also as expected, she is slowly starting to weaken - she is a bit weaker now and is back to being a borderline cat 3/cat 4 storm with winds of 130mph, central pressure of 948mb. 

The outer bands are over Mexico:

But it's mostly rainfall at the moment, not too overly stormy (technical term ;-)). Generally, I see that the convection (rainfall) has decreased a bit and, more interestingly, the west side is not as robustly round as it was compared to the imagery from yesterday:

This is because there is dry air to the north and west, but also because there is some wind shear - this is what I was hoping to see today. Long may that continue! So what do these satellite images mean and where do you find them? I think it's time for a double feature of a <Technical AND Forecasting Alert!>. Lucky you! 

<Technical AND Forecasting Alert!> Satellite Imagery: I mainly use three sorts of satellite images: visible (geocolor), water vapour (spelled with a ‘u’ of course ;-), and infrared. To access these, go to this NOAA website: https://www.star.nesdis.noaa.gov/goes/index.php. Click on the tab marked 'Storms' at the top, and the storm you are interested in the drop down menu. That page should load up with the Geocolor satellite imagery - the visible imagery... it is what you would see if you took a colour photo. Best used during daylight hours of course! ;-) This is useful to see the full extent of the outer bands. 

The water vapour image is also pretty obvious…it shows how much water vapor there is in the atmosphere. To find these, on the same page, on the left panel, click the tab labeled 'Channel Loops' (usually with the name of the storm as well). Bands 8, 9, and 10 are the water vapour at different levels in the atmosphere (high, middle, and low). Living in LA, of course I like looking at the moving pictures... the animation loop or animated GIF in the list of options in each channel section. The yellow/orange/brown areas are dry air (think of parched desert colours) and any other colour indicates some amount of water vapor, with green being a lot (think of well watered lawns... just like ours will be in a couple of days!). This is what the mid-atmospheric level water vapour looks like for Hilary at the moment:

You can see the dry air to the north and west quite clearly. Dry air inhibits the storm from intensifying, and an area of humidity and water vapor helps a storm to keep going. To toggle between different water vapour channels from this page, above the image, on the left side of the screen you will see a drop down menu (next to 'Band'). 

My favourite is the infrared satellite imagery because not only does it show where the storm is, but it also gives us an indication of how strong it is and what sort of weather we have. To get to these, you can pick Band 11 - called cloud-top phase (or cloud top IR).

The colours represent how high the clouds reach into the atmosphere because they are based on the temperature at the top of the cloud (which is what the satellite sees). It gets colder the higher you get in the lower atmosphere (the troposphere - I'll talk about the troposphere tomorrow). So we can tell from cloud top temperature how deep (high up) the clouds are and therefore how strong the convection is! The red colours are very big high clouds with the coldest temperatures and blues and whites are lower, warmer clouds. The redder the cloud colour, the more active the convection, the stronger the storm. My general rule of thumb (having seen these images and lived under them at the same time) is that blue and green areas are mostly clouds, with some very heavy rainfall in the green areas. But as you get to the orange and red, you get thunderstorms and possible tornadoes (especially in the red/dark gray areas). <End Technical and Forecasting Alert!>

Back to Hilary... she is clearly being impacted by dry air and wind shear, and as she continues to move north, she will be moving over cooler water and also interacting more with land, all of which will lead to a continuing steady decrease in strength. But she is still a robust storm and that eye is a beauty, showing us that the circulation is still very strong, and I agree with the NHC that she will be a hurricane when she clips the Baja peninsula - I expect she will be a strong cat 1 or weak cat 2:

She's currently at 19.7N, 112.7W heading NNW at 13mph, which is a pretty good clip for a hurricane. 

As it's a Friday evening, I'll throw in another <Forecasting Alert!> just for you for fun! 

<Forecasting Alert!> Watches and Warnings: You may have noticed that the colour of the coastline in the track chart above has changed from yesterdays lovely, fluffy, spring-like pinks and yellows, to todays bold and dark blues and reds. This is because these regions have changed from a 'Watch' (the fluffy spring colours) to a 'Warning' (the dark bold colours).

A Watch means those conditions may occur in those areas... but then again, they may not. 

A Warning means that those conditions WILL occur in those areas within the next 36 hours. 

A Tropical Storm Warning means you should expect winds of 39-73 mph within the next 36 hours, and a Hurricane Warning means you should expect winds of 74 mph or higher in the next 36 hours. <End Forecasting Alert!> 

So even if the center of the storm hasn't reached the Baja peninsula, you can see that the winds will start to pick up on Sunday ahead of the storm. 

In case you need any hints on supplies (for Greg M. in San Diego), here is my general list... 

- water
- batteries and flashlight

- first-aid kit

- full tank of gas in the car (or petrol if you are like me) 

- canned food and non-electric can opener

- sunscreen

- insect repellant

- hand-held fan

- candles and matches

- fully charged smart phone and laptops

- batteries for the radio (if you have one)

- two tubs of ice cream (different flavours to avoid boredom)

- some ice cream cones (optional)

- twelve bottles of wine (mostly red – no point getting too many white if there is no power for the fridge to cool it in!),  

- a non-electronic wine bottle opener

- fixings for lychee martinis (for the fruit - very healthy)

- good books to read

- cheese

- bags of PG Tips in a ziploc bag

- more ice cream (doubles up as a source of water). 

As a storm approaches, you will need to start the day by eating up the ice cream... just in case the power goes out of course. ;-) 

More tomorrow (after I've been shopping! :-)). 

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.