Tropical weather update: El Niño could affect Atlantic hurricane season

[00:00:01]All right, good Friday evening everyone.

[00:00:03]David Paul here in the KOU 11 weather center. It's nine o'clock. Time for the tropical update. Uh been an interesting week. We actually got hit by a tropical storm this week, Arthur. However, because of large amounts of windshare, impacts from that tropical storm here in Houston Galveston were strangely like I've never seen such small impacts from a tropical storm that did put wind gust to 60 down in Galveston. We had some low wa low spots on Galveston and Balar. See a little bit of inundation from the wave action. But if you were to tell me that a a tropical storm this the low-level center would move right over Houston Galveston and as that lowle center was moving right over Houston Galveston we would not get a drop of rain I would say probably not but that's exactly what happened. So we uh we experienced something very strange this week and it was because of windshare. We're going to talk about the windshare. And in fact, we're going to begin by looking at the sea surface temperature anomaly here on this Friday. And just uh big picture, we're looking at the Pacific side, the Atlantic side. You can see without too much effort that sea surface temperatures here are a little bit above normal. And then over here on the Pacific side, they are a lot above normal, way above normal, especially here. This is the El Nino region, and we're in an El Nino right now. But just glancing at it, our temps in the Atlantic basin, the Gulf, the Caribbe, the Atlantic, they're they're above normal. They're not nearly as above normal as they were the last two seasons. So, we're cooler than the last two years. Cooler than last year, cooler than than the year before.

[00:01:48]Uh this is the El Nino region. You see how bright that stripe is? Those are the unusual warm waters off the coast of Ecuador. There's the Galopagos and uh that's that's unusual. We'll talk about that process here as we move along. So El Nino advisory has been issued. The Pacific basin is in an El Nino and that has impacts for the Atlantic hurricane season. It also has impacts for uh our winter weather and it's expected this El Nino will strengthen. It may end up being one of the strongest we've ever measured. Last time we had an El Nino like that in 98.

[00:02:26]We had tremendous storms uh hit the California and Pacific coast of the US and put in tremendous amounts of snow in the Rockies and the Sierras and the Shastas and the Syscus and and even the Davis Mountains uh in in Texas. Uh so we're going to we're going to talk about that as well. El Nino advisory. El Nino is active. On the Atlantic side, we're above normal, but not nearly as above normal as we were last year.

[00:02:55]Only a little bit above normal there in the Gulf and the Caribbe. So, El Nino, how does this form? Usually in a normal year, trade winds at the surface blow east to west, but sometimes they just don't blow. So, normally those winds would blow the warm water over to Indonesia, which allows for cool upwelling and you get a cooling of the Pacific waters off the coast of South America. But when the wind doesn't blow like it's happening now, that warm water just builds and builds and builds.

[00:03:25]There's nothing to blow it away. There's no upwelling of cool air from under cool water from underneath and the heat builds and you get you know hundreds of thousands of square miles where the ocean temperature becomes way above normal and that impacts the global flow and global weather patterns across the globe. Uh this is some satellite imagery from a couple of Elnos just to compare.

[00:03:50]This was the really strong one 97 97 98 huge El Nino. This is the one that eventually sent all the heavy snow. It was a terrible winter uh mudslide, snow, uh storminess on the west coast of the United States. That was in the winter season. And then 2015, there's another El Nino. You can see that that one's not nearly as strong as the one in 9798.

[00:04:14]Okay. So, so why can it reduce the storm count on the Atlantic side, the Gulf of America, the Caribbe, the Atlantic? It is because just oversimplification, windshare at the mid and upper levels is increased when you have an El Nino in the Pacific. The windshare is increased across the Atlantic basin. More windshare equals less hurricane activity. This is an oversimplification.

[00:04:42]It's not like this flipping a switch. It doesn't mean categorically that we're going to have a lower storm count this season, but statistically during El Nino years, we've had lower storm count mainly because of the upper level winds either blowing apart storms that exist, Arthur, or never letting storms develop in the first place. Why? To get a hurricane or a tropical storm to develop, you need an unshared environment. So there's no there's no strong winds cutting across the mid and upper levels to disrupt the developing circulation. It gets vertically stacked. That's a healthy hurricane.

[00:05:25]When you get shear, it tilts everything over. It interrupts and disrupts the circulation.

[00:05:34]Hurricanes can get weakened to tropical storms. Tropical storms can be dissipated. Developing storms never develop because of wind shear. That is exactly what we saw with Arthur. The circulation was there. We had a lowle circulation with Arthur sitting right over us. But the wind shear at the mid levels blew all of the thunderstorm activity 200 miles to the east into Louisiana.

[00:06:04]Windshare ripped apart Arthur.

[00:06:08]Uh, next names on the list, Bertha, Crisal, Dolly, Edward.

[00:06:12]To get to 14, which is a normal season, would be Nana. We'd get all the way to Nana.

[00:06:23]So, just a reminder, we are at the beginning of hurricane season. We quite often see very little activity this time of the year. Here we are, June 19th, right there. So, we are in the time when there's very little activity. And I've seen many, many, many seasons start with a June storm in the Gulf of the Caribbe Arthur.

[00:06:46]And then everything just goes silent until August, usually right around August 15th, which is right here. That usually is when things really crank up. And you can see statistically that's when we really off the races with our statistical peak of hurricane season.

[00:07:04]August 15th through about October 1st.

[00:07:08]That's the real that's when most by by a long shot most of the storms form.

[00:07:13]August 15th to October 1st.

[00:07:18]So we may not have much go on. And one of the other reasons, one of the big reasons if you're not in El Nino, why are there so few storms early in the season? Quite often this is the time when we've got a lot of convection over equatorial Africa. Here's equatorial Africa and then you've got the Sahara Desert to the north. So over equatorial you'll get thunderstorms that lift create boundaries and sometimes these can send outflow into the Sahara Desert. Very strong winds at the surface. So that kicks up dust, kicks up millions of tons over the year. Millions of tons of Sahara desert dust gets picked up by that mechanism and then the the east to west flow carries it out over the Atlantic and that usually sets up at around 5,000 ft or so. So, what you end up with is a dry layer or layer at 5,000 ft of sinking air and dry air.

[00:08:18]Warm dry air. Sinking air and dry air.

[00:08:22]You get a temperature inversion. You get a dry slot. Well, that can block storms that are trying to to develop. They just get it's putting a cap on the atmosphere here. This is where the dust is right now. So, we've got dust out here. It's quite common to have a lot of it early in the season. And quite often these storms that are kicking the dust up subside as we go into August, September, October. That's one of the reasons why we get increased activity that and by that time there's a lot more warmth to the ocean surface.

[00:08:53]So what's going on out here now?

[00:08:57]Technically, there is a little remnant of what was Arthur here, but the hurricane center is taking it off the board. It's not going to redevelop.

[00:09:06]You may get some scattered showers uh over Bermuda over the coming days, but there's no storm developing there.

[00:09:15]Look how absolutely quiet the Gulf is now. And as we look out here, where do we stand? No tropical development, says the hurricane center for the next seven days. That's the bottom line. But as you can see, there are a lot of moving parts that are sort of brewing in the background right now.

[00:09:32]Uh that's where we stand this evening.

[00:09:34]We are live KHOU 11 News at 10 with your news headlines, weather headlines, sports headline. US got a win today.

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