Tropical Depression 2: July 23, Update A

I thought it was about time to jot down a bon mot or two on the latest blobette. :-)

I have been watching the mini-blobette (officially known as TD2) as she left Africa and zoomed across the Atlantic. She has been struggling, and at the moment there is very little circulation in the lower half of the troposphere and the convection has just decreased:

She is currently centered at 13.9N, 53.2W and is moving WNW at a very rapid 20mph. This blobette really doesn't have much to it, so it's pretty tricky to see where the center is actually and this location is as good as any other.

She is heading to the Lesser Antilles, and the folks there should be getting ready for it by making sure they have enough fixings for their umbrella drinks. It should be a lovely breezy day, maybe a little overcast with a drop or two of rain.

The forecast is for this system to dissipate any moment now and just be a low pressure trough by the time it moves over the Lesser Antilles. There are a couple of reasons for this. First, the wind shear is not very high, but high enough to hinder this blobette from getting the curling iron out. And second, the blobette is running into a bit of dry air:

(I don't know what they did to the colours of the normal water vapor map because these are horrible). The dry air as that dull dirty icky yellow shaded stuff.

However, so far she has been moving over relatively cold water (sea surface temperatures of less than 26.5 deg C - the temperature needed to sustain a storm). She's about to enter an area where the water temperatures are warmer than 26.5 deg C, with the upper ~100m being warmer than 26 deg C. This should sustain the convection at least and there is a chance she'll have more than one or two drops of rain as she crosses the Lesser Antilles.

I do agree with the NHC that she is too weak to amount to much, but I am still going to keep an eye on her. I'll be back with more if she does strengthen, otherwise I will spend the time watching really old black and white episodes of Dr. Who. :-)

Cheerio for now!
J.

Blogs archived at http://jyotikastorms.blogspot.com/
Twitter @JyovianStorm
-------------------------------
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 the National Weather Service announcements. This is not an official forecast. If I "run away, run away" (Monty Python), I'll let you know.
-----------------------------

July 4: Hurricane Arthur, Update A

Happy Independence Day America! A historic day indeed! In honour of today I won't mention that apple pie was an English dish from at least the 1380s or that baseball was played in England in at least the 1740s. Instead, because I'm a nice person (grin), here's a completely different fun fact for you: In 1776 some of the founding fathers (and mothers) of America were as old as Millennials are today (Millennials were born between the early 1980s and 2000)! Details here.

'Hurricane' King Arthur (he's not really one anymore as you will see) is officially at 41.2N, 68.7W, moving  to the NE at a whopping 31mph! This is too fast for a tropical storm and is the first indication that he is no longer a tropical storm, but is an extratropical system and has merged with a low pressure front.

His winds are 75mph, central pressure is officially still 976mb. Although 75mph winds means he is officially a weak cat 1 storm, but I agree with the NHC today because they have actually already said that he isn't a hurricane and have explained that they are being generous with this estimate of winds speed for now. When a storm merges with an extratropical front and has such a fast forward motion, one would expect high winds, even if it isn't a tropical storm/hurricane any more.

The satellite images clearly show how Arthur's appearance has changed over the last few hours:

 

The hint of an eye he had has vanished, his structure and circulation has also pretty much disappeared, and there is much less convection. I expect they will downgrade him tomorrow, so this is my last entry on 'King Arthur of the Nights of the Round Storms'.

I'll be back when we have another one out there. I hope everyone had a safe and fun day! :-)

Toodle pip!
J.

Blogs archived at http://jyotikastorms.blogspot.com/
Twitter @JyovianStorm
-------------------------------
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 the National Weather Service announcements. This is not an official forecast. If I "run away, run away" (Monty Python), I'll let you know.
-----------------------------

July 3: Hurricane Arthur, Update A

I think I'll launch right into the thick of things today...

Hurricane Arthur just made landfall between Beaufort, NC and Cape Lookout. Officially as a cat 2 storm with winds of 100mph.

Intensity:
Hurricane Arthur's official wind speed is 100mph, which makes him a weak-to-mid level category 2 hurricane (cat 2 range: 96-110mph). Central pressure is 976mb. I *almost* agree with this! I think he was this strong earlier today, but now he has started to deteriorate. It looks like he maxed out as a weak cat 2 storm a few hours ago, with winds in the 96-100 mph range, but is now a cat 1 again (cat 1 range: 73-95mph). But I'm glad that at least the NHC did finally call him a hurricane by this morning and then upped the intensity to catch up with the real world! Phew. No rant today!

You can see why I think he is deteriorating in the visible and infrared (IR) satellite images. Here is the latest visible satellite image:

 

You can clearly see a solid eye, which indicates winds of at least 85-90mph. But as he is interacting with land, the convection is decreasing. From yesterday's <Technical Alert!> you can more easily see what is happening with the convection from the infrared (IR) satellite images. Here's one I saved about 9 hours ago:

There was very strong convection in Arthur then - lots of thunderstorms and possible tornadoes as well as an eye. All signs that he was a robust cat 1/weak cat 2 earlier today. Now here is the latest IR image:

 

A marked difference! Dry air as well as his interaction with land has taken a bit of a toll. There is still some heavy convection, but it has greatly diminished in structure (not so 'solid' any more), which indicates dry air in the system.

He is definitely still a cat 1 storm, but I doubt very much that when he made landfall he was a cat 2 with 100mph winds! The NOAA station at Cape Lookout (the closest station to the eye) has so far recorded maximum sustained winds of about 77mph (sustained winds are the defining number to find in defining a storm, not gusts) as the eye-wall passed overhead, as you can see here (the eye passing over it is why the winds suddenly dropped):

(Wind speed is recorded in knots, and 1 knot = 1.15mph)

The circulation structure (vorticity) in the troposphere also shows the earlier increase in strength today and weakening now, again suggesting a stronger cat 1/weak cat 2 storm some hours ago, but now it is back to where it was yesterday evening... a cat 1 storm.

Track:
His center is at 34.7N, 76.6W and he is heading NNE at brisk 18mph. He passed to the southeast of Wilmington, NC earlier today and just made landfall north of Beaufort, NC as he continues to on his way up the US East Coast. It looks like the track shifted slightly to the west since yesterday, but definitely remained in the cone of tracks. Not much to add on the track front.

One of the impacts from this storm is, of course, the storm surge!  It had reached a maximum of about 1.5 ft above normal in Wilmington, but it is now just under normal. This is because the eye has passed and water is being pushed offshore by the winds instead of onshore. Whereas the water level at Beaufort has just peaked at about 2ft above normal (as the eye went by) and is now decreasing as the winds have turned and are pushing water offshore.

<Technical Alert!> To look at the storm surge, I use NOAA’s National Ocean Service website, Tides Online, which is an excellent site: http://tidesonline.nos.noaa.gov/geographic.html. Click on the state you are interested in, and then the location within that state. For example, here is the data from Beaufort:

The top graph shows the water level. In this graph, the red line is the actual observed sea level, the blue line is what the predicted water level would be because of the tides, and the green line is the difference between the two. The height of the green line gives you the storm surge level.  The graph below that is wind speed (which you can see was increasing) and direction. Below that is air pressure (which you can see dropping), and below that is air and sea surface temperature. <End Technical Alert!>

So far the reports I have from North Carolina (Wilmington) are that things are ok. Good luck out there! Stay safe if you are in the stormy area.

Everyone else... Happy July 4th!

Ciao for now,
J.

Blogs archived at http://jyotikastorms.blogspot.com/
Twitter @JyovianStorm
-------------------------------
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 the National Weather Service announcements. This is not an official forecast. If I "run away, run away" (Monty Python), I'll let you know.
-----------------------------

July 2: Tropical Storm Arthur, Update A

Tropical Storm King Arthur of the Nights of the Round Storms is officially at 30.6N, 79.1W, heading N at 8mph. And officially, his winds are now 70mph and central pressure is 988mb.

Winds of 70mph makes him a very strong Tropical Storm (TS range: 39 - 73mph)/borderline cat 1 hurricane. I think he is already a hurricane and has been since yesterday, but at least he continues to remain a little hurricane for now (although he is getting stronger). My reasons for knowing that he is a little hurricane (other than just using The Force) are:

1. Since yesterday he has shown signs of trying to develop an eye. An eye will form with winds of 85-90mph and higher (cat 1 range: 74 - 95mph). The fact that it is not there all the time suggests that he is a weak cat 1. You can see it trying to form in this latest visible satellite imagery:

2.  The circulation (vorticity) throughout the troposphere is now stronger than it was yesterday, including in the upper levels (see yesterday's <Science Alert!> about tropospheres), which is a clear signal that he is a hurricane and is actually getting a bit stronger.

3. The dry air and a bit of wind shear is keeping him in check, so he is not a strong hurricane. Although he looks like he has an eye that is surrounded by clouds in the visible image, the clouds are not evenly spread around the storm, as you can see in this infrared satellite imagery:

This shows that there is pretty decent convection all the way around the eye that you and I can see... but that the NHC can't!! Actually... <Minor Rant Alert!> I can't believe the NHC haven't upgraded him!! He's approaching a mid-size cat 1 with winds in the 80-90mph range, not a 'Tropical Storm' with 70mph winds!! How is this storm not a hurricane?? Grrrr. <End Minor Rant Alert!>

<Technical Alert!> Satellite Imagery: I mainly use three sorts of satellite images: visible, water vapour, and infrared. The visible one is obvious… it is what you would see if you took a black and white photo. Best used during daylight hours of course! The water vapor image is also pretty obvious…it shows how much water vapor there is in the atmosphere. Brown areas are dry (think of parched deserts) and any other colour indicates some amount of water vapor. The infrared satellite image is the most interesting though 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. 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 troposphere (as I mentioned yesterday), so we can tell from cloud top temperature how deep the clouds are and therefore how strong the convection is! The red colours are very big high clouds with the coldest temperatures (other than a dark gray), and blues and whites are lower, warmer clouds. The redder the cloud colour, the more active the convection. My general rule of thumb (having seen these images and lived under them at the same time) is that blue and yellow areas are mostly clouds, with some rain in the yellow 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 Alert!>

So, it looks like some extremely strong convective activity on the east side of that thing we shall call an 'eye', and some rather strong convective activity on the west side.

Track: I see they have moved the track slightly to the west, bringing it to North Carolina tomorrow night and on Friday, pretty close to the South Carolina border...

so, umm... Wilmington, are you ready? (Gee, I hope no-one just moved there to start a new job or anything... Got those bottle of wine ready? How about the ice cream?) The track may change a little - maybe move slightly further west - but overall it looks reasonable to me. If any of my on-the-ground reporters have photos or reports (I recall some plant damage photos from Wilmington a few years ago), let me know!

At the moment it looks like he will be a cat 1 by the time he gets there because of the dry air and wind shear. The thing to watch out for is if the eye forms and stays fully developed - that's an indication that he's a strong cat 1 and slowly approaching cat 2 intensity.

More tomorrow. Good luck with the preparations out there.
Over here, it is ice-cream o-clock!
J.

Blogs archived at http://jyotikastorms.blogspot.com/
Twitter @JyovianStorm
-------------------------------
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 the National Weather Service announcements. This is not an official forecast. If I "run away, run away" (Monty Python), I'll let you know.
-----------------------------

July 1: Tropical Storm Arthur, Update A

I just managed to get onto the interwebs after a long day of travel and meetings and eating of cheeses...

... and while I was busy doing all that, it looks like Tropical Storm Arthur was busy getting stronger. Currently the official winds are at 60mph, but I think this may be a bit too low. It looks like TS Arthur has good circulation in all levels of the troposphere (ooh... I feel a <Science Alert!>  coming on! ;-)), which is the signal we would only see in a hurricane! I think at some point today he may have reached borderline TS/cat 1 winds (around 75mph)... but there is so much dry air around that convection has not really taken hold, which stopped him from growing much beyond that and he may actually be weakening now as a result.You can see that Arthur been 'lanced-a-lot' by dry air (tee hee hee) in this infrared satellite image movie:

<Science Alert!> The troposphere. Our atmosphere is divided into layers – like a trifle or seven-layer dip or lasagna (depending on what country you are from). A characteristic of each layer is that 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 to about 15-16km in the equatorial regions, and to about 8km in the polar regions of the planet. All our 'weather' essentially occurs in the troposphere. It is defined by decreasing air temperature with increasing height. You would know this if you climbed a mountain or you could just use the much easier 'Florida option', which is to look at pictures of mountains and see the snow at the top. J 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. The layer of the atmosphere above the troposphere is called the stratosphere, which is defined by air temperature increasing with height. The ozone hole is in the stratosphere. <End Science Alert!>

Weak storms have circulation in the lower sections of the troposphere, but hurricanes have circulation throughout the troposphere - and this is what we are seeing with Tropical Storm Arthur.

Officially winds are 60mph, central pressure 1001mb, and he is at 28.0N, 79.1W, heading Northward at a slow 4mph. Given the clear eye, the location is almost spot on (I'd say 28.1N, 79.1W) and he is moving NNW.

Here is the visible satellite movie for Tropical Storm Arthur, just because.

More Tales of Arthur, The Round Storm tomorrow.
Night night!
J.

Blogs archived at http://jyotikastorms.blogspot.com/
Twitter @JyovianStorm
-------------------------------
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 the National Weather Service announcements. This is not an official forecast. If I "run away, run away" (Monty Python), I'll let you know.
-----------------------------

June 30: Tropical Depression One, Update A

Here we go! The first Tropical Depression of the Atlantic has been named as Tropical Depression One! (surprise! ;-)) (meanwhile in the Eastern Pacific we're on Tropical Storms number 4 (Douglas) and 5 (Elida)).

Officially he has winds of 35mph, central pressure 1009 mb. In case you are wondering, a Tropical Depression (TD) is a system with closed circular motion (as you see in the "movie" below) and maximum winds of 38mph. I really think he became a TD much earlier in the day today ... here's what he looked like at around 4pm EST:

So I'm glad the NHC finally upgraded him to TD 1 in the 11pm EST advisory!

Like the circulation, the convection has slowly improved during the day too, mostly because of the ocean. He is over warm water, with sea surface temperatures over 29 deg C, and he is interacting with the Gulf Stream which is a current that  runs along the eastern edge of Florida (and the southeastern US) and has warm water over a large depth; the upper ~50-75m of the water column are warmer than 26 deg C. The atmosphere (which has a moderate amount of wind shear and dry air) and his proximity to land have been keeping him in check. This 'battle' between the ocean, atmosphere and land has been going on all day... but it looks like the ocean is slowly winning because the convection is slowly increasing, as you can see in the infrared satellite image:

Actually, with this heavy convection over his center of circulation, I think he is already a Tropical Storm!

His center is officially at 27.6N, 79.1W and he is moving South-Westward incredibly slowly at 2mph. I think he may be a bit to the east of this location, but I agree with the snails pace movement - he must be really enjoying those 'umbrella' drinks in the Bahamas! ;-) The forecast track has him turning to the west (towards Florida) and then eventually north, skirting the Florida and Georgia coastline over the next couple of days:

I think this is a very likely path and as the NHC were quite good at the 1-2 day track forecasts last season I have little reason to doubt this. It is tricky to tell whether he will actually reach the Florida coast but whether or not he does, he will bring rain and possible coastal flooding to parts of eastern Florida. And because he is moving so slowly this may cause a few hiccups so get the wellies out and put the ponies in a barn!

He is going over the Gulf Stream, which usually means intensification, so although officially the Tuesday and Wednesday forecast calls for a maximum wind speed of 50-60mph, I wouldn't be too surprised if he turns out to be a bit stronger (aka Tropical Storm 'Count Arthur Strong' - a very zany British show! :-)). As I mentioned earlier, the dry air and wind shear will inhibit him somewhat so we'll have to see how that battle plays out.

Travel day tomorrow but I will try and hop onto a computer (not literally of course - that would look quite silly and also damage the computer ;-)) and send an update!

Toodle pip!
J.

Blogs archived at http://jyotikastorms.blogspot.com/
Twitter @JyovianStorm
-------------------------------
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 the National Weather Service announcements. This is not an official forecast. If I "run away, run away" (Monty Python), I'll let you know.
-----------------------------