Stormy East Coast

Various stuff, mostly my absent-mindedness, is keeping me from doing a video today, so I'll mail it in... I mean, write something up today and throw in a pretty picture or two.

The first order of business today is dealing with the prolonged period of wet weather and wind that's going to be hitting the mid-Atlantic for a few days here. I talked about this yesterday but it deserves some more time today. The developing storm off the Carolinas now is already causing winds of gale force over the water and it still hasn't fully pulled Karen's remains in yet. The area between the Outer Banks and southern New Jersey is going to get hit hard over the next couple of days with some wind, rain-pounding surf and coastal flooding. It's not a tropical storm but it might feel like it for a while. I think our forecast that goes onto AccuWeather.com is generally in touch with the situation at this point, so you can see your local forecast for the details.

The frustrating thing is that the computer models that showed nicer weather with the storm pulling away at the end of this week are not showing that today. I'm not too surprised by that since things are getting pretty blocked up over eastern North America and the western Atlantic (negative NAO for y'all geeks out there). Well, that's really frustrating for y'all up in Delmarva who will see the lousy weather continue for a while. I'll be down in Charleston south of it all and loving it!

One area benefiting from the storm will be Florida. Northerly flow around the storm will pull dry air into the rest of the Southeast and the big difference will be in Florida, where very muggy tropical air is going to go away for a while. That's going to put a stop to most of the afternoon thunderstorms for a while. It's about the time of year for that to start happening, so y'all shouldn't be too surprised. Tomorrow and Thursday, there will be some spotty showers and thunderstorms popping up in the afternoon, mainly over South Florida, but by the weekend it will be so dry that I doubt we see any rain down there at all. It will take a while before it moistens up again, too, perhaps as late as the middle of next week.

Here's one picture to help describe this:

This is the GFS precipitable water forecast for Saturday evening. Precipitable water is a measure of the water available in the atmosphere, the amount of precipitation that would fall if all the water over a given location were converted to rain. Normally in the summer and early fall in Florida, it's relatively high, say 1.6 inches or so. Well, you can see the model is forecasting it to be under an inch over most of Florida. It's awfully hard to make afternoon thunderstorms when the atmosphere is that dry. So, we think it will stay mainly dry down there this weekend.

On that same picture, you see moisture swirling around the storm near Delmarva still. You also see that precipitable water is pretty high back in Texas by this point and there's a band of moisture that stretches toward the Great Lakes. All this moisture comes from two sources. Well, most of it comes from the tropics, because by this point the wind will have turned out of the south for a while and that will pull Gulf of Mexico and Caribbean moisture into the area. A front moving in as evidenced by that band of moisture toward the Great Lakes will turn that moisture into showers and thunderstorms. That front will arrive late Thursday into Thursday night in the High Plains and panhandles, but at that point moisture will be pretty limited and most of the thunderstorms will pass by to the north. That's a good thing: we're in the second severe season right now and these storms will be doozies with wind, hail and a few tornadoes. There's a decent chance these nasty storms will get as far south as I-40 but probably not much farther south than that. The upper support for that storm system will heat northeast, so the old front will get left behind over West Texas and western Oklahoma through Friday. By Friday, the moisture levels will be better but with no upper support it probably won't do much along the front. Another piece of upper-level energy (weather geeks: a vigorous shortwave trough) will move in on Saturday and that should light up the radar with thunderstorms once again. Perhaps there is a few severe storms. By Sunday, the upper energy is lacking but the front will be there and there will be a lot of moisture around. As you can see from the picture above, precipitable water should already be up to 1.5 inches or so and in some cases is over 2 inches (non weather geeks: 2 inches of precipitable water is a lot). So, just the moisture and the southerly flow into the front should be enough to get thunderstorms going. The very moist environment around there should lead to some locally heavy downpours.

Early next week as another storm crosses the country, we should see the front start heading eastward but the rate at which that happens is in question. Slower is probably better in my opinion, even the slower models may be too fast. And, the front may be very slow to move through South Texas, so repeated downpours will become a concern next week.

In the tropics, we have only one named system on our side of the world, Narda in the East Pacific.

That's it on the far left side of this picture. We figured it would be a hurricane for a while today, but it sucked in dry and stable air to the north, so it weakened instead and is barely a tropical storm at this point. At this point, we think it will fall apart completely in a day or so. Either way, it's out in the middle of nowhere and no real threat to anyone. Note the other blob southwest of the Gulf of Tehuantepec. That is going to be something to watch. It will take a few days if it's going to happen, but the models are showing it trying to become a tropical cyclone and perhaps affect southern Baja California or northwestern Mexico next week. Maybe some moisture from it eventually gets pulled into Texas, but that's many days away.

Now, for the Atlantic. Here's a look at the Caribbean this evening:

The remains of Karen are getting entrained into the storm off the Carolinas and there's a tropical wave south of Puerto Rico. The wave will have to be watched as it heads west, but it's not likely to develop with upper winds aloft unfavorable and causing shear. (Weather geeks: the MJO remains unfavorable for now, but one more wave of upward motion should move over the Atlantic in 7-10 days, lasting for perhaps two weeks. That ought to mean one last hurrah for our hurricane season then, probably.)

I wish I had a better satellite view but there is one area of interest out by the Cape Verde Islands still, which I mentioned yesterday. Models show it trying to develop into something name-worthy in the coming days, but like a lot of storms out there, it looks as though it will stay out in the Atlantic and be no real threat to anyone. It's still out there on the GFS on the 22nd when I get back from vacation, so maybe I'll get to talk about it then.

Well, that's all I have for you today. Speaking of vacation, that begins for me Thursday. I'll do all I can to get one more post up here tomorrow before I go, but it will be a busy schedule tomorrow, so no promises. At this point I am not planning any meet and greet because I am going to the NWA meeting in Charleston while down there and that's going to keep me pretty busy for five of the days I'm down there. But, if something opens up, follow me on Twitter (@AccuFrank) as that is where I'll announce it.

As always... y'all be good!

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