LRandyB's Tropical Weather Discussion

Tropical Weather Discussion for September 27th

By: LRandyB, 11:51 AM GMT on September 27, 2007

Good morning folks! Just a quick update...

TD#13 is getting a little better organized. It may be too little too late as the storm is very near the Mexican coast. NHC is expecting it to become a strong TS before making landfall tomorrow.

Karen is looking well defined but shear has completely exposed the low level circulation this morning. All the convection is well east of the low level center. The biggest concern here is that if Karen loses all it's upper mid and upper level definition, then the steering flow would be primary low level. This would indicate Karen would continue a westerly motion rather than recurve toward the north at the approach of an upcoming trough. Of course, that won't matter much if the low level circulation of Karen falls apart too once it loses it's upper level circulation. So we'll have to wait and see how this plays out.

An area of showers and thunderstorms over S FL had temporarily developed a low level circulation over Key West yesterday but that faded away over night and there is no real obvious organization of this area this morning. NHC forecasts some possible devlopment over the next couple of days off the east coast of FL.

A tropical wave south of the Cape Verde Islands is being watched but doesn't look too impressive on satellite this morning.


Tropical Weather Discussion for the Week of September 23rd

By: LRandyB, 4:04 AM GMT on September 24, 2007

Good evening folks! Sorry it's been so long since the last update. Between flying Dean and Felix, vacationing, and catching up on work, it's been hectic. And the tropics are, once again, becoming somewhat active. There are four tropical systems in the Atlantic basin that we're watching right now. Only one is actually a designated tropical storm but I wouldn't be surprised to see at least two more in the next 48 hours. Let's get to it....

In the Gulf ....

The big news here is a trough of low pressure extending from the Yucatan peninsula northward into the north central Gulf of Mexico. We've had rain at my house quite a bit today from this system. The biggest thing I can say about this trough is I am glad it wasn't there a week ago when I was cruising in the Gulf and western Caribbean! :-) In the upper levels a strong low pressure center and associated trough is centered over south central Texas. Between the strong southerly flow aloft over the western half of the Gulf and the subsiding air over that region, the weather is beautiful west of about 92W. A high pressure center can be found in the upper levels just north of the Yucatan Channel. The anti-cyclonic circulation associated with this high covers pretty much the entire eastern half of the Gulf and is helping to enhance showers and thunderstorms associated with the trough of low pressure that extends from the Yucatan northward at the surface. Areas in the central and eastern Gulf coast states have been getting some much needed rain over the last 12-24 hours. NHC has been watching this area for possible development but there has been no indication of organization or any well defined circulation center in the low levels. Recon flights scheduled for today were postponed until tomorrow. By then I think the threat from this area will be minimal. None of the models forecast development of this system.

In the Caribbean...

This is probably the one area of the tropics we really don't have much to talk about. But that will change as invest 97L works its way into the Caribbean in a couple of days. The western Caribbean is under the influence of the circulation around the upper high just north of the Yucatan Channel. This is producing some scattered showers west of Jamaica. Water vapor loops show a well defined upper level low just south east of Jamaica and an upper high over the tropical wave approaching the Windward Islands (97L). The flow between this low and high is producing some fairly strong southerly winds aloft and some strong shear over the east central Caribbean but that is forecast to relax over the next 24 hours. There is no real weather associated with this low. Generally speaking, except for the extreme western portion, the Caribbean weather is nice.

In the Atlantic ....

First I'll talk about Tropical Storm Jerry as there isn't a lot to talk about. Jerry is in the north central Atlantic moving north and is barely holding on to tropical storm status. Satellite shows it to be sheared with the approach of a mid-latitude low pressure system that will absorb Jerry by about the 24 to 36 hour point. And Jerry is not expected to strengthen before that happens. So it doesn't look like anyone will have to worry too much about this storm.

Next we have a tropical wave, designated invest 97L, located near 12N 57W or about 300 miles east of the Windward Islands. This system is sitting in an area of light shear and the shear is not forecasted to increase over the next few days. Water vapor shows an area of anti-cyclonic turning overhead this wave which is helping to enhance shower activity and in fact, this system has seen a gradual increase in organization over the last 24 hours. The best model guidance available at the moment brings this system over the Windward Islands and into the northeastern Caribbean Sea before encountering Puerto Rico and Hispaniola where the interaction with terrain would likely hinder any further development. If this system takes a more southerly track, then it would miss the larger islands of the Greater Antilles and stay in an area of forecasted lower shear. Combined with the warm water in the Caribbean, this would allow this wave to become a hurricane in the central Caribbean according to the SHIPS intensity model.

Lastly, we have invest 96L. This is a strong tropical wave located a few hundred miles southwest of the Cape Verde Islands near 8N 30W. This one will bear some watching but we have lots of time to watch it. The wave was analyzed by the TPC to have a 1007MB low at its center. It does already exhibit good upper level outflow and some banding so it's a safe bet we'll see this one become a tropical storm in the next couple of days. Beyond that, at the moment, it's hard to tell what this system will do. The models that are providing guidance tend to recurve it pretty quick out in the central Atlantic but none of the models have a good handle on this system yet and the most reliable models we have don't even develop this wave. However, as I've said before, the models don't do a good job of handling the initial cyclogenesis of tropical systems. Recurvature from a system this far south seems unlikely right now. However the fact that it is this far south means it won't be able to get too wrapped up just yet since it's too close to the Equator. We'll have to wait until this system becomes better developed before the models will be able to get a good handle on it.

Whew! Ok.. that's it for now! We've sent some planes to the Caribbean to start flying 97L and be there when 96L gets there. In the meantime, we're flying 94L (the Gulf system) from here if needed tomorrow.

It's that time of year! I'll update more frequently as these systems develop.


Tropical Weather Discussion for the Week of September 16th

By: LRandyB, 5:46 PM GMT on September 15, 2007

Hi folks! Well, the season "feels" like a pretty normal one. Of course, two back to back Cat 5 hurricanes making landfall (for the first time in the Atlantic Basin) is far from normal but this is certainly nothing like the 2005 season.

This will be a short suammry. I'm headed out the door on a short vacation. Believe it or not, I'm headed on a cruise with my wife into the Caribbean. I know, don't say it! I've heard it enough. Why would a Hurricane Hunter book a cruise in the Caribbean at the peak of hurricane season!? Hey.. I got great rates and it actually looks like the weather will cooperate! :-)

Right now, there are two main areas NHC is watching in the tropics. There is Ingrid which was just downgraded to a depression and at the moment, I wouldn't hold my breath waiting for it to redevelop. But there a slight chance 2 or 3 days from now when the upper level shear relaxes a bit that Ingrid could become a TS again before moving out into the open Atlantic.

The other area they are watching is mid-Atlantic near 14N 38W. But this area is not very organized and will move into shear over the next couple of days too.

So for the moment, I think we have a bit of a break. Which is good for me since I'll be on a ship in the Caribbean! :-)

Have a great week!



Catagory 5 Hurricane Felix

By: LRandyB, 12:30 PM GMT on September 03, 2007

Good morning folks! My flight got back on the ground safe and sound.We didn't get quite the rough ride NOAA 43 had but we got bounced around enough.

Felix continued to intensify as we flew it. The pressure dropped from 936 mb on our first pass to 931 by our second pass and our sonde didn't quite the center so the pressure was probably a bit lower than that. It's tough to nail it when the eye is so small.

The eye was probably the best eye I have ever seen in a storm. Perfectly round, beautiful stadium effect. I didn't think we'd see much in the dark but the moon was just over the top of the eyewall cloud and there was more lightning then I have ever seen in a hurricane. So I got some cool shots. I'll post them!

One of our pilots captured some video during the first eyewall penetration. You can view that here

Updated: 1:04 AM GMT on September 07, 2007


About LRandyB

I was an AF aviation weather forecaster for 12 years, then 15 years as a dropsonde systems operator with the AF Reserve Hurricane Hunters.