Masters student in tropical meteorology at FSU. Raised in Alaskan blizzards, but drawn toward tropical cyclones by their superior PGF.
By: Levi32 , 4:48 PM GMT on June 26, 2009
Tropical Tidbit from 12:30pm EDT Friday, June 26, 2009:
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The main feature today is the area of disturbed weather in the western Caribbean that I've been watching since Wednesday. This area has now been designated "Invest 93L" by the NHC, which is nice because we can start to get some model runs on it today. What happened overnight is the mid-level circulation came north out of Honduras and into the western Caribbean, while the tropical wave to the east has moved in with the axis now just west of the Caymans. This has resulted in lots of convection going off in the area east of the mid-level low. The NHC is only talking about the tropical wave right now because they like to focus on surface features. Because of this they put the center of 93L on the wave axis NE of Honduras, where a buoy nearby registered a rapid pressure fall and a wind shift from S to NE earlier this morning. Pressure at the buoy has since risen almost as fast as it fell but just in the past hour has reported falling pressures again, which are pretty high to begin with at around 1013mb.
So, how strong is it going to get? Well with the trough-split over the western Yucatan backing SW it's setting up a nice upper high over the western Caribbean which is ventilating the disturbance, allowing it to breathe, as well as providing low wind shear. This, along with obviously warm SSTs in the area, means we could see some gradual organization of 93L over the next 24 hours. Within 36-48 hours 93L's northwestward motion is expected to carry it over the Yucatan, which will delay significant organization for a while. I don't expect anything big to come of this during its time in the Caribbean, as it still needs time to consolidate and get a surface low going before it can do anything. If a surface low does form it will likely initiate along the tropical wave axis. This wave is already amplifying so we will have to watch for for that today and tonight. Formation of a closed well-defined surface low will likely result in 93L getting upgraded Tropical Depression 2. For the moment there is nothing significant going on at the surface.
Ok, but where will it go? Will it threaten the north gulf coast? There is an upper weakness to the north over western Florida that is pulling north on 93L, but the trough-split to the west is acting as a westward pull on it, as well as trying to build a nosing ridge north of the system. These factors all combine to give a NW motion which should take 93L towards the NE Yucatan and eventually into the southern Gulf of Mexico. Thereafter is when things get tricky. As the trough-split feature leaves the area 93L will be left under an area of very weak steering currents, and the last several runs of the GFS have kept it in the Gulf of Mexico for up to 5 days before going anywhere. However the latest 12z run that just came out takes it through the channel and into SW Florida.
This is where I need to mention one of the things to remember about models is that they jump around a lot with the track. I expect they will be particularly jumpy in this situation because when you get weak steering currents there are usually many possible tracks. The main factor determining when 93L can move north again after getting into the GOM is the trough off the US east coast. If it digs far enough south, a track through the weakness to the NE like the latest GFS shows is possible. If the trough stays further to the north like most of the other models are showing, a more westward track would ensue under the pull of the westward flow on the south side of the subtropical high over the NW gulf coast. Right now it's still a bit too far out, and all we know for sure is that 93L will be moving NW in the vicinity of the Yucatan and eventually into the southern Gulf of Mexico.
The bottom line here is we're going to have a tropical disturbance moving into the southern Gulf of Mexico in 2-3 days that has a shot at developing, and everyone along the gulf coast should keep an eye on it. Hopefully if it gets drawn north it can provide some much-needed rain for somebody, which is not a bad thing at all.
There is another area to keep an eye on, and that is the tropical wave over the eastern Atlantic, which will probably be forgotten amongst the excitement close to home. The wave has mid-level turning with it with scattered moderate convection. Some organization is possible over the next few days as the TUTT lifts out and upper winds become marginally favorable. Don't write it off just because it's early in the year. Climatology is a poor excuse to ignore the current situation. At any rate this wave will not be affecting any land areas anytime soon.
We shall see what happens!
Invest 93L Visible Satellite: (click image for loop)
Invest 93L model tracks:
The views of the author are his/her own and do not necessarily represent the position of The Weather Company or its parent, IBM.