Invest 95L Brushes Louisiana Coastline

By: Dr. Jeff Masters , 12:42 AM GMT on July 06, 2010

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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).

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ok this is what it look like We might have all 97L, 98L, and 99L between the next 2-10 day from now one form the wave at 40W that new wave comming off of africa coast and the other near Burmuda
Member Since: June 13, 2009 Posts: 2 Comments: 12716
1969. gator23
Quoting ackee:
WHAT will become of 96L

A TD
B TS
C HURRICANE
D STRONG TROPICAL LOW

e. Nuthin
Member Since: Posts: Comments:
Quoting Patrap:
Product: NOAA Temp Drop (Dropsonde) Message (UZNT13 KWBC)
Transmitted: 6th day of the month at 22:27Z

Aircraft: Gulfstream IV-SP (G-IV) (Reg. Num. N49RF)

Mission: Non-Tasked Mission, possibly not tropical (flight in the North Atlantic basin)

Mission Identifier: Al96 (Probably storm name and mission number)


Observation Number: 18


Tropical jet hitting as hard in NOLA as Mobile? Lots of precip here.
Member Since: Posts: Comments:
1967. gator23
Quoting justasking:


Thanks Cosmic! I have to admit I've had to bite my tongue a few times over the years.

i think you have posted before. i remember your handle very clearly.
Member Since: Posts: Comments:
1966. ackee
WHAT will become of 96L

A TD
B TS
C HURRICANE
D STRONG TROPICAL LOW
Member Since: Posts: Comments:
1965. Patrap
Product: NOAA Temp Drop (Dropsonde) Message (UZNT13 KWBC)
Transmitted: 6th day of the month at 22:27Z

Aircraft: Gulfstream IV-SP (G-IV) (Reg. Num. N49RF)

Mission: Non-Tasked Mission, possibly not tropical (flight in the North Atlantic basin)

Mission Identifier: Al96 (Probably storm name and mission number)


Observation Number: 18
Member Since: July 3, 2005 Posts: 428 Comments: 129841
1964. beell
I don't think either feature has an easy path to development over the next 24 hrs at least. Even if the Yucatan feature stays low in latitude it still has some dry air to contend with.

The east side of the surface trough in the GOM is under 30-40 knots of shear. Maybe more. The strong lower level flow is almost perfectly in opposition with the upper flow.
Member Since: Posts: Comments:
1963. Patrap
Member Since: July 3, 2005 Posts: 428 Comments: 129841
Quoting CosmicEvents:
Welcome in. 6 years...first post.
You have the patience of Job.


Hice hat...welcome...
Member Since: Posts: Comments:
Alright, I'm out for the night. I say the mid-level low is still the one to watch (over the Yucatan). It has all the upper support, just needs to work its way down to the surface. It also has the most time to work with, although not more than 3 or 4 days. I think it will become Bonnie and make landfall around the same area as Alex. See ya.
Member Since: Posts: Comments:
Quoting justasking:


Thanks Cosmic! I have to admit I've had to bite my tongue a few times over the years.
OK Taz, That proves it. He is not him cause he would never just sit there and bite his tounge....LOL
Member Since: Posts: Comments:
1958. Levi32
Quoting justasking:


Thanks Cosmic! I have to admit I've had to bite my tongue a few times over the years.


Lol....I bet. Welcome :)
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1957. Levi32
Quoting Dakster:
OK. So at 8pm EST what is everyoen thinking the NHC will say? How many circles (or at this point just circle the entire GOM)


It should be one circle in the same spot as the last TWO, and I see no reason why the percentage would change from 30%.
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Quoting CosmicEvents:
Welcome in. 6 years...first post.
You have the patience of Job.


Thanks Cosmic! I have to admit I've had to bite my tongue a few times over the years.
Member Since: Posts: Comments:
1955. Dakster
OK. So at 8pm EST what is everyone thinking the NHC will say? How many circles (or at this point just circle the entire GOM)
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Quoting justasking:
check out buoy 42001 on the NOAA site



(first time posting, but have lurked since 2005)
Welcome in. 6 years...first post.
You have the patience of Job.
Member Since: August 3, 2005 Posts: 10 Comments: 5684
1953. KEEPEROFTHEGATE (Mod)
INV/96/L
MARK
21.1N/87.3W
Member Since: Posts: Comments:
Quoting Patrap:
GOM 84 Hour Wave Forecast Model(using MIKE21)


Thanks for pulling that out, Patrap. Interesting loop for sure.
Member Since: July 15, 2005 Posts: 3 Comments: 1270
sorry, what low?

Member Since: Posts: Comments:
1950. JLPR2
Quoting Levi32:
The Yucatan low has vorticity stacked at all levels up to 500mb. The surface trough in the central gulf is limited to 850mb.





check out the one near 40W and 10N it shows up on both maps too, well I hope convection stays far away from it :)
Member Since: Posts: Comments:
Quoting MiamiHurricanes09:
Anticyclone now over the vort max.



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.
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1947. JLPR2
Quoting MississippiWx:


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.


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
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1946. Levi32
The Yucatan low has vorticity stacked at all levels up to 500mb. The surface trough in the central gulf is limited to 850mb.



Member Since: Posts: Comments:
Quoting justasking:
No, I'm not the infamous JFV. And I've never owned a fish shower curtain in my life. But, have taken a few meteorology classes at TAMU in CS, and have been a fan of weather my whole life. Enough about me though, back to the tropics!



ok i was this makeing sure
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Quoting MiamiHurricanes09:
Anticyclone now over the vort max.



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.
Member Since: Posts: Comments:
1943. Levi32
Quoting scott39:
Correct me if im wrong, but doesnt the NHC draw smaller and larger circles, because developement can happen inside that circle?


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.
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96L's circulation stacked somewhat in the 500mb through 850mb levels.
Member Since: September 2, 2009 Posts: 130 Comments: 21194
1941. Levi32
The upper anticyclone over the mid-level low indicates that the main heat buildup is still over the Yucatan instead of farther north. Lots of thunderstorms will continue to go off in the northern gulf due to the big surge of southeast wind that is creating strong convergence. A surface trough in this situation is not particularly likely to close off.
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Quoting Levi32:


No the mid-level center and the surface center got divorced.

What did they do with the house, though? ;)
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1939. scott39
Correct me if im wrong, but doesnt the NHC draw smaller and larger circles, because developement can happen inside that circle?
Member Since: Posts: Comments:
No, I'm not the infamous JFV. And I've never owned a fish shower curtain in my life. But, have taken a few meteorology classes at TAMU in CS, and have been a fan of weather my whole life. Enough about me though, back to the tropics!
Member Since: Posts: Comments:
1937. Patrap
#1934

..U betcha
Member Since: July 3, 2005 Posts: 428 Comments: 129841
1936. JLPR2
the mid gulf is hotter than the area where the mid circulation should be landing



In other words, I think that the surface circulation might be up to something.
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Quoting Patrap:
Seems schul is in again on the wunderground..

LOL


Purple drank, gold chains. At least JM held up the colors........
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I'm getting a little more impressed with the GOM circulation than the Yucatan circulation, IMO.
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Anticyclone now over the vort max.

Member Since: September 2, 2009 Posts: 130 Comments: 21194
1931. beell

Link
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21:00 UTC CIMSS 850mb vorticity shows a stronger NE Yucatan circulation and a weaker "low" in the middle of the GOM.

Member Since: September 2, 2009 Posts: 130 Comments: 21194
1929. JLPR2
Quoting Levi32:


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.


ha!, nice thanks for clearing that up :)
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1928. Levi32
Quoting Hardcoreweather2010:
Did 95L have a baby ?



No the mid-level center and the surface center got divorced. You don't usually get children in that situation...
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Quoting MiamiHurricanes09:
He's not. Just stop. JFV always comes back with a handle picture and a name like "LaNina" or "THCP".


ok
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1926. JLPR2
Quoting Hardcoreweather2010:
Did 95L have a baby ?



that's one big baby considering 95L's size LOL!
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1925. Patrap
Seems schul is in again on the wunderground..

LOL
Member Since: July 3, 2005 Posts: 428 Comments: 129841
Quoting hydrus:
You did it now Taz.....I see the shower curtain..how is that disturbance doing in the Gulf?


96L is right where the NHC forcasted....mid gulf. Most lost him but I've been following. 97L later. Hello Pat.
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Quoting MississippiWx:


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.
Nor am I. Basically a naked cyclonic swirl in the middle of the GOM.
Member Since: September 2, 2009 Posts: 130 Comments: 21194
Did 95L have a baby ?

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Quoting GeoffreyWPB:
We most likely will get Bonnie out of 96L within a few days.
It will have to be within a few days or else it will move overland.
Member Since: September 2, 2009 Posts: 130 Comments: 21194
1920. Levi32
Quoting JLPR2:


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?


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.
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Jeff co-founded the Weather Underground in 1995 while working on his Ph.D. He flew with the NOAA Hurricane Hunters from 1986-1990.

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