Invest 95L Brushes Louisiana Coastline
Hi all,
Dr. Rob Carver, filling in for Jeff this week.
Midnight CDT Update
The low known as Invest 95L stopped it's northward progression and is now moving west along the Louisiana coastline. This is the oddest mesoscale convective complex/tropical feature I've seen in awhile. It's still producing a lot of rain, 2+ inches inland and 6+ inches over the ocean.
Base reflectivity from Lake Charles, LA at 11PM July 5 showing a very nice comma head. Animated loop.
Invest 95L is making landfall now in southern Louisiana near Terrebonne Bay. A CMAN station in Terrebonne Bay is currently reporting winds from the SE at 21 mph and the pressure is 1009 mb. Looking at the radar data, Invest 95L never had convection around the center of circulation. Also, it was hard to see a distinct surface circulation in the different analyses available. I believe soaking rains for southern Lousisana are going to be Invest 95L's main legacy. It's already produced 5+ inches of rain in some offshore locations according to radar-derived rainfall estimates.
Fig. 1 Meteogram for TRBL1 in Terrebonne Bay, LA. Tabular data are here.
Fig. 2 Base reflectivity from New Orleans, LA at 706PM, July 5. Animated loop.
Invest 96L
430 AM Update
In sum, the 00Z model runs don't present a different picture. It is curious to note that the Canadian Global model does not intensify 96L at all in the 00Z run, while NOGAPS has shifted towards a SE Louisiana landfall. I think the following discussion is still valid.
96L is going to be an interesting feature to forecast. It's still on the edge of a strong wind shear gradient. 40+ knots of shear are on the NE side of 96L, and <10 knots are on the SW side. The "center" of 96L is under about 15 knots of shear. This is likely inhibiting 96L. Nearly all forecast models take 96L NW through the Yucatan peninsula and into the Gulf of Mexico. Near the Yucatan itself, sea-surface temperatures are relatively cool, not the best environment for intensification. However, at 25N, 87W there is a hotspot of SST's, which would promote rapid intensification. However, there's currently 20 knots of shear over the hotspot, so the thunderstorms that do form as a result will be well ventilated, and not cause 96L to intensify.
The dynamical models have different takes on how 96L intensifies in the next 120 hours. The 18Z operational GFS strongly intensifies 96L over the hotspot and takes 96L towards Grand Isle, LA. The parallel (for testing model configuration changes) GFS has a similar track, but does not strengthen 96L as much. This indicates uncertainty on how the models are handling the upper-level winds.
The 18Z HWRF solution is much like the parallel GFS solution. The 12Z Canadian global model has a more westerly track, pushing 96L towards Port Arthur, but it strengthens 96L right before it makes landfall, not when it's over open water. NOGAPS takes the "a little from column A, a little from column B" approach, with a spinup over the hotspot (op. GFS solution), but a westerly landfall (the Canadian solution). More data to initialize the models from synoptic reconnaissance flights will help reduce uncertainty.
The bottom line, 96L will move into the Gulf of Mexico and is then shrouded by the mists of uncertainty. I also think that it's a possibility (>50%) that it will become a tropical cyclone sometime in the next 48-72 hours (leaning towards sometime in day 2-3 based on the model runs.)
Fig. 3 Plot of maximum winds (mph) for the next 120 hours from the 18Z July 5 GFS model run.Parallel GFS version.
Fig. 4 Plot of maximum winds (mph) for the next 120 hours from the 18Z July 5 HWRF model run.
Fig. 5 Plot of maximum winds (mph) for the next 120 hours from the 12Z July 5 CMC global model run.NOGAPS wind swath.
Next update
I'll probably tweak this blog later tonight as new model runs come in. I'll have a full update tomorrow afternoon (Pacific time).
Reader Comments
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Bonnie?
doing good
Maybe take a Gander at the GOM IR loop. Shear is das Kaput and a warm column may be forming.
Shear, Like gas..always passes
haha!
These year we seem to have some very strong mid level circulations with the surface lacking.
So is it easier for a circulation to go from the mid levels downwards or the other way around?
Knock it off Taz....
AOI
Actually I'm rather impressed those handles were even available LOL!
The sharks vs. the jets.
I'm not impressed at all with the Central GOM area. I see a slight cyclonic rotation, but it's not even half-way closed off. It will run into land before it ever gets started due to the fast Southeasterly flow it is embedded in.
In the tropics it is easier for a surface circulation to build upwards because that is what tropical cyclones do naturally. Working a mid-level circulation down to the surface is harder.
96L is right where the NHC forcasted....mid gulf. Most lost him but I've been following. 97L later. Hello Pat.
LOL
that's one big baby considering 95L's size LOL!
ok
No the mid-level center and the surface center got divorced. You don't usually get children in that situation...
ha!, nice thanks for clearing that up :)
Link
Purple drank, gold chains. At least JM held up the colors........
In other words, I think that the surface circulation might be up to something.
..U betcha
What did they do with the house, though? ;)
Pretty much, but the circle is usually centered over where they think the center of the disturbance is. The size of the circle generally corresponds to the size of the disturbance.
Very consistent with satellite imagery as well. A blow up of convection over the Central GOM doesn't mean that the circulation there is taking over. A lot is going on there to cause that convection. I don't believe it has anything to do with a surface circulation. Has more to do with diffluent flow aloft, a trof of lower surface pressures and a lot of moisture. The area over the Yucatan is still the one to watch.
ok i was this makeing sure
Considering that one is over land and the other over water, yeah, that could explain why convection is moving to the other for the moment, well...
I have no idea then LOL! XD
Defiantly a positive note for 96L, with an anti-cyclone situated over head shear will be less of an issue. And vort as you mentioned has increased over the Yucatan another sign that the MLC is indeed beginning to take over as the main circulation of 96L.
check out the one near 40W and 10N it shows up on both maps too, well I hope convection stays far away from it :)
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