T.D. 12 forms, Gulf of Mexico development possible mid-week

By: MississippiWx , 10:32 PM GMT en Agosto 29, 2011


Tropical Depression 12 formed early this morning in the Eastern Atlantic from the African wave that had been tagged 92L the past couple of days. It is the main feature in the Eastern half of the Atlantic. The Western Atlantic is very active convection-wise today. The convection is being aided by a lingering boundary left behind by Irene, a surface trough of low pressure moving across the Western Caribbean, and an upper level low pressure system near Puerto Rico. The upper low is causing divergence aloft as it interacts with the surface features to the west, forming the convection near Bermuda as well as aiding in convective development with the Western Caribbean surface trough. The Gulf of Mexico is quiet for now, dominated by upper ridging and NW flow aloft.

Atlantic Wide View

TD 12 Discussion

Tropical Depression 12 had its first advisory issued at 5AM this morning. The NHC has discussed the current issues with easterly and northeasterly shear which is causing the system to be heavily weighted to the west. I discussed in my last blog that I believed TD 12 would strengthen gradually, rather than quickly until it reached 50W. I am still sticking by that statement and the NHC agrees as they have the wind speed strengthening 15mph after TD12 moves past 50W. The reasoning for that is the sudden jump in tropical cyclone heat potential as well as a less sheared environment.

TCHP: Notice the spike at 50W

We also discussed in last night's blog that the models had TD12 moving too far north and I am still staying with that statement. The reason for my track goes hand in hand with the strength forecast. The strength is going to have a lot to do with how far north TD12 goes before reaching the longitude of the Antilles. With a more gradual intensification, I don't expect 92L to gain much latitude until after it reaches 50W. I believe you can put the pieces of the puzzle together and figure out why I believe that. After 50W, a more true WNW motion should begin and this should put TD12 (Katia) dangerously close to the Northern part of the island chain, as well as Puerto Rico. It remains to be seen just how much of weakness forms from a cut-off low to mid-level low pressure system, which would be located to the northwest of then Katia. The strength of the low will determine the size of the weakness. It is interesting to note that the 12z run of the European is much weaker with that low, and thus sends Katia on a more westerly course after missing the islands to the north. The pattern is favorable for landfalling U.S. tropical cyclones, with a neutral to weakly positive NAO. However, we must not forget about our friends in the islands as they may have to deal with Katia before us, just like with Irene. I'm not going to speculate on a path after the islands as that is nothing more than a guess at this point. However, I feel fairly confident in a track directly at or just north of Puerto Rico at this time.

Model Plots:


Elsewhere, we may need to watch closer to home before we even worry about Katia. The models are starting to latch onto the surface trough of low pressure that is moving northwest in the Western Caribbean. The trough is helping to ignite a good deal of convection today and it should be closely monitored the next few days. Until today, the NAM was the only model being aggressive with development. However, the Euro jumped aboard at the 12z run, which is enough for me to really respect this wave's potential. The GFS had hinted at this possibility several runs back, but dropped it and is possibly picking back up on it during the 12z run. We will need to pay attention to this wave as the Texas ridge lifts out to the north and northwest and opens the Gulf just enough for development to occur. It should be easier for any disturbance to develop now than it was with Don when the Texas ridge was firmly in place, causing shear and subsidence across the Gulf. Upper level conditions may not be ideal, however, so I don't expect anything stronger than a moderate tropical storm for now. The water temperatures in the Gulf are warmer than any other ocean basin in the world, so we must respect what can happen if upper level support is adequate. At this time anywhere from Central Louisiana to South Texas looks to be at risk from the possible tropical cyclone. We still have a few days to watch, so stay tuned.

Gulf of Mexico SSTs

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14. GeorgiaStormz
9:10 PM GMT en Junio 20, 2012
new blog time!!!!!!
Member Since: Febrero 11, 2012 Posts: 0 Comments: 9897
13. originalLT
9:47 PM GMT en Mayo 14, 2012
Post # 12, I think you are getting "hot and bothered" by an old Blog. Look at the time and date stamps.
Member Since: Enero 31, 2009 Posts: 0 Comments: 8012
11. SPLbeater
7:32 PM GMT en Agosto 31, 2011
GOM scarily hot....anything that gets in there without much shear/dry air interfearance could seriously have a long period of RI
Member Since: Agosto 4, 2011 Posts: 46 Comments: 4566
10. MississippiWx
5:34 PM GMT en Agosto 30, 2011
Thanks, everyone!
Member Since: Julio 15, 2006 Posts: 17 Comments: 10301
9. weatherganny
5:19 AM GMT en Agosto 30, 2011
Great Information...Thanks!
Member Since: Agosto 8, 2008 Posts: 0 Comments: 220
8. biloxibob
5:08 AM GMT en Agosto 30, 2011
Quoting MississippiWx:

Thanks, Kori. I always enjoy your blog updates as well.
Excellent update.
Member Since: Agosto 21, 2011 Posts: 0 Comments: 138
7. MississippiWx
4:49 AM GMT en Agosto 30, 2011
Quoting KoritheMan:
Good update. Keep doing them!

Thanks, Kori. I always enjoy your blog updates as well.
Member Since: Julio 15, 2006 Posts: 17 Comments: 10301
6. KoritheMan
4:44 AM GMT en Agosto 30, 2011
Good update. Keep doing them!
Member Since: Marzo 7, 2007 Posts: 644 Comments: 23119
5. MississippiWx
10:59 PM GMT en Agosto 29, 2011
Thanks! Hope to have you here to read them.
Member Since: Julio 15, 2006 Posts: 17 Comments: 10301
4. Thrawst
10:57 PM GMT en Agosto 29, 2011
Great update! Hope to see more of these! :)
Member Since: Julio 18, 2010 Posts: 52 Comments: 2016
3. MississippiWx
10:49 PM GMT en Agosto 29, 2011
Thanks, guys. Should be an interesting week for sure.
Member Since: Julio 15, 2006 Posts: 17 Comments: 10301
2. hahaguy
10:44 PM GMT en Agosto 29, 2011
Thanks Great info. Another one we gotta keep a close eye on.
Member Since: Agosto 12, 2007 Posts: 2 Comments: 2886
1. WeatherNerdPR
10:44 PM GMT en Agosto 29, 2011
Thanks. Katrina to be is moving west ATM, and that West Caribbean AOI looks interesting.
Member Since: Julio 7, 2010 Posts: 0 Comments: 5726

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