Homegrown development this weekend

AccuWeather

AccuWeather's Bernie Rayno explains the factors setting up to form storms in the tropical waters.

Transcript

00:00Now, I'm in my own little studio here for the forecast feed where I break it all down

00:05and I show you all of the tools that I use, or at least some of them, to make a forecast.

00:12I want to talk about homegrown development.

00:16We may get that this weekend.

00:19I'll explain why.

00:19What is homegrown development?

00:21Take a look.

00:22It is the interaction between the jet stream and the tropics.

00:25You usually see this during the early part of the hurricane season as you get in June and July,

00:32and then as you get into October and November.

00:35So as the jet stream comes south, what does it bring down into the tropical waters of the Caribbean and the Gulf?

00:42Upper lows and frontal boundaries, which can do what?

00:46Form storms.

00:48Now, once a storm forms, it's usually a cold core storm.

00:52Why?

00:52Because the jet stream is not coming from the tropics.

00:55It's coming from northern latitudes.

00:57But if you can get that energy or low pressure to sit over the warm waters for a minimum of 48 hours,

01:05so two days at minimum, you can translate that storm into a tropical system.

01:11Okay.

01:11Having said that, what about this weekend?

01:14We're talking about a tropical rain and windstorm.

01:17Well, take a look at the upper air pattern here as we go through today.

01:21You're getting this dip in the jet stream, this upper low, remember?

01:24That was, remember, what did we talk about?

01:26We're going to go back to that.

01:27Upper lows, there it is, coming south.

01:30So interaction between the jet stream in the tropics and an upper low going over warm water?

01:37Yes.

01:37Let's go back to that.

01:38Watch the energy as we go forward here.

01:41Okay.

01:41I'm going to put this into motion.

01:43This is showing the energy coming east.

01:46Here it is.

01:47Upper low.

01:47As we get into Friday night, you're starting to get the energy right in here off the southeast coast of the United States,

01:54and then that energy lifts northward.

01:56So it produces a surface storm.

01:58When?

01:59Beginning Friday night.

02:00Now, it's very weak.

02:02It's around in here.

02:03Let's go to Saturday, late Friday night.

02:05There is the storm forming right there.

02:07Let's say Saturday morning.

02:08So the clock is ticking because this low pressure system off the Florida coast is going to be going where?

02:16Over the warm water of the Carolinas here.

02:20Let me show it to you really quick.

02:22So there's the warm waters.

02:23So this low pressure system forms here, and it'll be moving in the water temperatures of over 80 degrees.

02:31Now, here's the key.

02:32This storm has to be over this warm water for a minimum of 48 hours to translate this storm into a tropical system.

02:44Does it do that?

02:45Well, the clock's ticking here, so here we are.

02:48Here we are Friday, Saturday morning, late Friday night.

02:51What happens?

02:52Well, it moves forward.

02:53There we go.

02:54Here we go.

02:55Here we go.

02:55So we're about 24 hours.

02:57It's still off the Carolina coast, but watch what happens as we get into Sunday morning.

03:01So this would have to go to Monday morning, right?

03:05It's gone.

03:06Here it is by Sunday afternoon.

03:08It's in here off the North Carolina and off the Virginia coast.

03:14What are water temperatures there?

03:16Let's take a look at them.

03:17A lot cooler.

03:18See, once you get into here, once you get into here, you lose that 80 degree waters.

03:24So to me, when you look at homegrown development, did we reach the checklist?

03:29The answer is no.

03:31You do not have this over the waters for 48 hours.

03:36That's why this, while it will have the feel of a tropical storm in the mid-Atlantic, no

03:42doubt about that, with the impacts being quite severe, this is going to be a damaging storm.

03:47I don't think that this will meet the criteria for a tropical system so you won't get any homegrown

03:52development.

03:53Now, we're not done talking about homegrown development because we have problems in the

03:59Caribbean here.

04:00I've been talking about this for the last period of time here because look at the water temperatures

04:06here across the Caribbean.

04:08These are the anomalies.

04:10What's the anomaly?

04:11It compares the current water temperatures to history.

04:16And what you're seeing here with these yellow, red, and oranges, you're seeing water temperature

04:21anomalies about three to four degrees above the historical average.

04:26What does that mean?

04:28That means this water is super duper warm.

04:30You're looking at water temperatures in the middle to upper 80s.

04:34Okay, with that in mind, I want to go back.

04:38I want to go back to our modeling here because there is a little bit of a concern as we head

04:43toward next week.

04:44Here's why.

04:45The same dip in the jet stream that we're worried about producing our tropical rain and

04:51windstorm here may be able to spin something up in the Caribbean and the Gulf because look

04:58what's going on.

04:59Look at the dip in the jet stream.

05:01You see it right in here.

05:03Look at that dip in the jet stream.

05:04Now, this is Sunday evening.

05:06So you're bringing a frontal boundary far south and you're going to start getting showers

05:11and thunderstorms to be located in this area.

05:15Okay, what does the wind shear look like in this area?

05:19We have a product for that.

05:20Let me show it to you.

05:21It's right here.

05:22Okay.

05:23Now, the wind shear rips storms apart, right?

05:27The way you see the dark colors, the reds, the yellows, and oranges, you have a lot of

05:30wind shear.

05:31So you have a lot of wind shear in the Gulf, but you see this little pocket here, right

05:35in here around Jamaica and south of Cuba, there's low wind shear.

05:39What does that look like moving forward in the next week?

05:42Look how, oh my goodness.

05:44By Tuesday and Wednesday, look at this, you have low wind shear.

05:47Now, by this time, your dip in the jet stream has left.

05:51See, here it is Sunday.

05:53See how it leaves?

05:54But one wonders, do you have enough showers and thunderstorms going on in the northern part

06:00of the Caribbean?

06:01Because if you do, there's low wind shear.

06:04Look at the light colors here.

06:06So again, I've showed this before, but we're going to have to keep an eye on this area.

06:11Homegrown development underneath that high pressure system as the trough leaves.

06:17That's a story in the feed.

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