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With two named storms, Arthur and Bertha, having formed so far this Atlantic hurricane season, AccuWeather's Bernie Rayno looks ahead to August while monitoring the tropics for potential development.
Transcript
00:00Closing in on the month of August, and of course, as we go through August, the hurricane season ramps up
00:04very quickly.
00:05I'll show you that in a second.
00:07So far this season, we've had two storms, right where we should be, two tropical storms.
00:12The third tropical storm historically, or third storm historically, is early August.
00:18So we're right on track with a normal hurricane season.
00:21We typically don't see the first hurricane, though, until August 11th.
00:25We are now in what I call the doldrums of the hurricane season.
00:29We got birth of the form.
00:30But from July 15th to August 15th, we usually don't get much in the way of tropical development.
00:36You lose the homegrown development because you lose the interaction between the jet stream and the tropics.
00:41And the tropical Atlantic, usually still pretty quiet due to wind shear and dry air.
00:47If we do get any development from now through, let's say, the middle part of August, this is where it
00:54would occur.
00:54It would be off the east coast of the United States and into the Gulf in this area.
00:59Now, this is not a low probability of development.
01:03Some people I see online talking about it having a low chance for development.
01:07That's not what we're saying here.
01:09What we're saying here is that the Atlantic Basin is shut down for development, except in this region.
01:16Any development would have to occur here.
01:18I'll show you why in a second.
01:20And right now, there's not really any signs that anything would develop.
01:25But that's where you got to watch.
01:27When you look at the hurricane season, you know, you would think as you go deeper and deeper into the
01:35season that you would more likely get storms in July than June, right?
01:42It is interesting to note, you see this little bump up in June.
01:47Then once you get to July, it kind of flattens out until about August 3rd.
01:51And then you start seeing an increase after about the 15th or so.
01:55So this is what I call the doldrums of the hurricane season.
02:00Sometimes, not always, you get less storms in this period than what you do from July 15th through August 15th
02:06than what you do during the month of June to mid-July.
02:10There's a reason for that.
02:12And this time of the year, the Atlantic Basin has problems with a lot of dry air.
02:22I want to show you the water vapor loop.
02:23Take a look at this.
02:24This is the west coast of Africa.
02:27Here is Dominican, Hispaniola, Puerto Rico.
02:31These are the lesser Antilles.
02:33Look at how much of the tropical Atlantic is covered in dry air.
02:38This is what we call Saharan dust, right?
02:41And that shuts down tropical development.
02:43What happens is you get these tropical waves coming off Africa.
02:47But as they come and move to the west, there's all this dry air in place.
02:52So none of them really develop.
02:54Also, what you tend to have is strong wind shear.
02:58Take a look at the wind shear product.
02:59Look at the amount of wind shear you have in here across the Caribbean and also into the southwest Atlantic.
03:06Now, yes, you've got this zone in here off Africa, although this is pretty far south for development.
03:12But you have this area where you have low wind shear.
03:15But if I take you back to the water vapor loop where you have low wind shear, what do you
03:21have?
03:21You have a ton of dry air, right in here.
03:25Look at all the dry air.
03:26See?
03:26So that's why it is unlikely to get development this time of the year in the tropics.
03:32Instead, you need development near the United States when you get a dip in the jet stream interacting with the
03:40tropics.
03:40And that usually occurs in the Caribbean, off the southeast coast of the United States, and also in the Gulf.
03:45Now, let me show you what's going to be happening here moving forward.
03:50I want to show you the east coast infrared satellite picture.
03:54And when you get a dip in the jet stream, what ends up happening is, is that the dip in
04:01the jet stream brings frontal boundaries and upper lows into the tropics where you can get showers and thunderstorms.
04:08Do you see what's going on here?
04:09You've got a front in here, right in here, right in here.
04:14And along that boundary, you notice what you're starting to see.
04:18Let me draw that boundary again.
04:19You notice what you're starting to see with that boundary?
04:23Along it, you're starting to get showers and thunderstorms along that boundary, right?
04:30And that begins the process for tropical development.
04:38Now, in order for these showers and thunderstorms to become a tropical entity, you need to have low wind shear,
04:46warm water, and you have to get those showers and thunderstorms to sit over the warm water for at least
04:5348 to 72 hours for this to become a tropical system.
04:58Now, if you have any dips in the jet stream, as long as this dip sits there, the better possibility
05:06that you do have for tropical development.
05:08I want to show you the upper air pattern in this area over the next, let's call, week or so.
05:16So, do you continue to see a dip in the jet stream there?
05:19And the answer is yes, you do.
05:21Let's go out in the middle.
05:22See, right in here, what you have going on here, you've got a high here and a high pressure here,
05:29right?
05:29So, you've got this little dip in the jet stream in here.
05:32This is as we get in the middle part of next week.
05:35In fact, early part, you just continue to get this little dip in the jet stream.
05:39There's Thursday.
05:40Now, it lets up a little bit Friday at next week.
05:44And then, here's your next dip as we get into the 12th and 13th.
05:49You see that?
05:49Coming in across the east, this will go all the way down.
05:53So, early part of the week, next week, you have the dip in the jet stream.
05:57Then, it goes away and then it comes back as we get toward the middle part of August.
06:01Now, it's not strong, quite honestly.
06:06You can't see showers and thunderstorms denoted down across the southeast.
06:10I don't see anything in this area that is going to organize.
06:15However, with those dips in the jet stream, right, and then when you look at the wind shear in this
06:23area,
06:23this is early next week, where you see the blues.
06:26You see how you start by the time we get into late next week?
06:29Look at this area.
06:31You don't have any color.
06:33That's low wind shear.
06:34Now, the rest of the Atlantic is shut down.
06:37So, that's why we say, listen, it's probably going to be quiet.
06:41However, if you do get any development in the Atlantic Basin,
06:46this is the area to watch moving forward.
06:51We'll keep an eye on it, and so should you.
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