Thursday, September 01, 2016

Hurricane Gaston, Tropical Storm Hermine, TD8, Tropical Storm Madeline, Hurricane Lester: August 31, Update B

After traveling all day, I am writing from another planet where I've seen dancing dinosaurs (so cute), R2-D2 (always cute), and the hulk in a kilt (not cute). Meanwhile back on Earth, I've developed a new management tool to keep track of all the storms! It's called 'Making-A-List' on a 'Piece of Paper' with this device called a 'Pen'. It's so great, I can even use it when there is no power, and replacement parts are really cheap! ;-) 

Hurricane Gaston - Atlantic
He's been fluctuating between being a cat 2 and cat 3 storm today. At the moment he's a strong cat 2 with winds of 105mph (cat 2 range: 95-110mph), central pressure 970mb. He is heading NE at 20mph and is currently at 36.0N, 45.4W.

He is actually caught up in both some strong wind shear, but also a front. His lower and mid-tropospheric vorticity (circulation) is that of a tropical storm system, but his upper level vorticity is now part of a front, so he is a hybrid system and is transitioning to being a front. This is why he has such a fast forward motion (20mph is really quite speedy for a hurricane!). You can see the wind shear in his satellite imagery...
 ... the convection is streaming off to the northeast of the eye. I would agree that he is a cat 2 storm though, because he is maintaining a pretty strong eye structure, despite the wind shear. However, it does look like he is weakening as that eye is beginning to collapse. 

He's about a day or so out from the Azores and given how he is deteriorating now I expect that he will be no more than a Tropical Storm by the time he gets there, which matches the official forecast:
Be ready for a breezy day, with some rain!

Tropical Storm Hermine - Gulf of Mexico
I heard it was "raining cats, dogs, pigs, goats - the whole barnyard in the Tampa Bay area" this morning (thanks for the note Al H.). Photos of the flooding have also been pouring in all day (all puns are intended), with a lot of flooding in areas that are prone to flooding of course. It looks like quite a mess along parts of the western coast of Florida. 

Hermine is mid-size Tropical Storm now with winds of 60mph (TS range: 39-73mph), central pressure 998mb.

She is currently at 25.8N, 87W, heading NNE at 10mph. Her track takes her into the Florida Big Bend area by tomorrow evening/Friday morning:
As I've said before, the NHC are now pretty good at the track one day out - better than me! so I will go with this. (At the moment, I personally think she'll be towards the eastern edge of that cone - near or south of Cedar Key, possibly just north of Tampa Bay - but that's because I can't see her center where they say it is, it looks like it is southeast of that location to me). The important thing is that it isn't really just where landfall will occur, and it isn't actually just about the glowing cone of whiteness (new technical term I just made up ;-)). Her convection is bigger than that, and another part of the impact will definitely be the storm surge.  

This is a bad approach as far as storm surge and flooding along the west Florida coast. Storms swirl in an anti-clockwise direction, which means they push water onto the coast as they go past. You can look at the storm surge from this Tides Online link. At the moment they have kindly pulled the links out for areas on the west coast of Florida to make it easy for you to see those, but in general click on the 'State Maps' tab on the left, and then click on the State you are interested in, and then the location within that State. For example, here is the data from Cedar Key, Florida at the moment:

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, so Cedar Key reached a maximum of over 2ft above normal and it is now declining.  The graph below that is wind speed and direction. Below that is air pressure (which you can see has been fluctuating), and below that is air and sea surface temperature. 

Although Hermine was named until later in the day, she wasn't solely responsible for this mess of rain. The fluctuating air pressure we see in the sensors along the coast suggests that things were more complicated than a straightforward tropical storm.   

Yesterday, we saw that the vorticity from this system was connected to a region of higher vorticity over Florida. Here are the latest maps for the lower troposphere, mid-troposphere, and upper troposphere:

You can see Hermine in the Gulf, marked by the sign for a tropical storm. If you look at the lower troposphere, you will see that her circulation is connected to another strong circulation area in the Atlantic, off the coast of South Carolina and over the Gulf Stream, and the connecting bands are over Florida. Both areas of low level circulation are over warm water, where the upper 75-100m of the water column are warmer than 26.5 deg C. This means they would generate a LOT of rain. 

However, now we are definitely seeing the outer rainbands from Hemine moving over Florida, so although today may not have been only the fault of a tropical storm, tonight and tomorrow will be! 
About tomorrow... the upper troposphere vorticity map shows some circulation in the upper troposphere associated with this storm. This suggests that Hermine is actually close to being a hurricane, if she isn't actually one already.

Here is her latest satellite imagery:
Although officially her winds are 60mph, I think they are closer to 75mph. I wouldn't be surprised if she was upgraded to a hurricane fairly soon. 

Tropical Depression 8 - Atlantic
Meanwhile, back in the Atlantic, TD 8 is now moving away from the US east coast in an ENE direction at a rapid 18mph. Winds are 30mph, central pressure is 1010mb. He is centered at 36.7N, 70.1N. Not much else to say about this baby, so I think this will be my last post on him. 

Tropical Storm Madeline - Pacific
I hadn't realized how many of you gentle readers were interested in the storms that visit Hawaii until I posted the update this morning on Madeline! Crumbs! I definitely need the TARDIS XPRIZE asap!! (plus, having time travel would really really help make my 'predictions' 100% accurate! ;-)).

So, quick update from this morning... 

In addition to that strong wind shear, you can really see that once she started to interact with the Big Island, she really took a dive (... into the Pacific to see the green turtles and other lovely things, not sharks... I had an encounter with three of those whilst snorkeling off Hawaii, but that's another story):

It looks like most of the rest of the island chain will get cloudy weather with some lighter rain as the Big Island is taking the brunt of the rainfall. Just a note, in case you missed it - the blue areas in the infrared imagery are generally just cloudy, then as you approach the orange, the rainfall gets heavier, and orange-to-red is thundery weather. Gray is not good. 

She is currently at 18N, 155.1W, heading WSW at 12mph (a very respectable speed for such a storm). Winds are now 65mph, estimated central pressure is 998mb, making her a strong Tropical Storm (TS range: 39-73mph).  Her center of circulation is to the southwest of the main convection. It is not that easy to see, but you can just about make it out in the visible satellite imagery:

She is forecast to pass to the south of the islands. She no longer has any circulation in the upper troposphere, just the middle and lower troposphere - another indication that she is no longer a hurricane. 

Hurricane Lester - Pacific
Lester on the other hand has circulation all over the place, and is most definitely a Hurricane. He is currently a major hurricane with winds officially at 130mph, central pressure of 954mb. This makes him barely a cat 4 (cat 4 range: 130-156mph).

He is at 18N, 139.9W, heading W at 13mph. His forecast track currently takes him to the north of the islands on Saturday:
He is also heading into the same wind shear that Madeline met, so he should weaken a bit before he gets there. He is not the best looking storm (partly because he looks like he is already running into that wind shear to the north) and really doesn't have the strong convection we would expect to see in a cat 4, so I don't think he is actually that strong - I think he may be a weak cat 3 actually (winds around 115mph). 

Phew! This is quite possibly the longest update I've ever written! Time to sleep now. 

Stay safe out there as almost all of these are interacting with land of some description or another!

Night from this other planet (set in Atlanta - where I expect to see some rain from Hermine!) 

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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 the National Weather Service announcements. This is not an official forecast. If I "run away, run away" (Monty Python), I'll let you know.

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