TD 18: the one to watch

By: Dr. Jeff Masters , 3:15 PM GMT on September 18, 2005

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The forecasters at the National Hurricane Center are pretty busy this weekend, writing advisories for two systems in the Atlantic and three in the eastern Pacific. Thankfully, Ophelia is finally gone, but we are watching another wave of the coast of Africa that might develop into a tropical depression. But for now, we can ignore all of these systems except one--Tropical Depression 18, which is expected to build into Tropical Storm Rita later today. The NHC agreed with this assessment last night, taking the unusual step of diverting a hurricane hunter airplane--the mission bound for Philippe was recalled and sent to TD 18 instead. The Florida Keys and Texas are at greatest risk from this developing storm.

Current status of TD 18
TD 18 is over the Turks and Caicos Islands, which one can think of at a western extension of the Bahama Islands. After an initial west-northwest motion last night, TD 18 has settled into a track 10 degrees north of due west which will take her through the Bahama Islands today and tomorrow, and threaten Cuba and the Florida Keys after that. TD 18 is devloping a little faster than Philippe did, and showing some solid deep convection over the center, good spiral banding on the northwest side, and some decent upper-level outflow on the north side. The shear over TD 18 has decreased steady the past 48 hours, and is now down to 5 - 10 knots, which should support some moderate intensification. This shear is expected to remain constant or decrease slightly over the next 24 hours. The upper-level winds look favorable--an upper-level anticyclone has developed on top and will provide favorable outflow. Water temperatures are very warm--30 to 31C. However, there are two factors which will probably prevent TD 18 from attaining hurricane status in the next three days:

1) An upper level low pressure system over Cuba and Jamaica. This upper low is positioned to the southwest of TD 18, and the counterclockwise flow of air around the upper low will bring 5 - 10 knots of shear to TD 18's southwest flank over the next few days. The upper low is forecast to move west and maintain it's position on the southwest side of TD 18. However, after three days, the low is forecast to weaken, which would generate the lower shear environment TD 18 would need to grow into a hurricane.

2) Interaction with Cuba and the Yucatan Peninsula. TD 18's current track may put it on top of Cuba Tuesday. One model, the UKMET, indicates TD 18 will cross Cuba and get tangled up with the Yucatan Peninsula. Interaction with either of both of these land areas will likely prevent TD 18 from attaining hurricane strength until it can clear them and get its entire ciculation into the Gulf of Mexico.

Track of TD 18
The strong ridge of high pressure steering TD 18 to the west is forecast to persist for the next five days. The computer models differ some on how strong this ridge will be after TD 18 clears the tip of the Yucatan Peninsula, with the UKMET and Canadian models taking the storm west-southwest into Mexico, the GFS and NOGAPS taking the storm towards south Texas, and the GFDL taking it into Louisiana. The strength of a trough of low pressure expected to swing across the Midwest U.S. late in the week will be crucial toward determining the where the storm ultimately makes landfall along the Gulf Coast. The strength of this trough is impossible to determine at this point. I believe that Texas is at greatest risk, judging by the current forecast guidance.

Intensity forecast for TD 18
Both of the major computer intensity forecast models, the SHIPS and GFDL models, make Rita a Category 1 hurricane by Wednesday, as it passes through the Florida Keys. It is unlikely TD 18 could intensify to a stronger than Category 1 hurricane before it hits the Keys, since it's current state of organization is relatively poor, and there will still be some shear of the southwest side affecting the storm the next two days.

Assuming the storm misses Cuba, there is nothing I can see to prevent Rita from becoming a major Category 3 or higher hurricane in the Gulf of Mexico by Friday. Shear is forecast to be light, and water temperatures are at record high levels. But if Rita hits Cuba or the Yucatan Peninsula, it will be difficult for her to regroup quickly enough to attain more than Category 2 hurricane strength.

Philippe
Tropical Storm Philippe continues to organize, and has all the appearance of a system on its way towards becoming a large a powerful major hurricane. Philippe's track looks good for everyone except the residents of Bermuda. I looked through the tracks of all hurricanes that passed close to the point where Philippe is forecast to be five days from now, a few hundred miles south of Bermuda. Only three hurricanes in the past one hundred years have gone on to hit the U.S. that passed through a location that far to the north and east. The longer range computer models do suggest Philippe may take a more westerly motion towards the U.S. late in the week, but the odds of a trough of low pressure picking up Philippe and recurving him out to sea are high. I seriously doubt Philippe will affect any land areas except perhaps Bermuda.

ITCZ disturbance
The Intertropical Convergence Zone (ITCZ), remains active. A tropical wave in the ITCZ located about 900 miles west-southwest of the Cape Verde Islands has acquired a low level circulation and some deep convection, and may grow into Tropical Depression 19 later in the week as it moves west-northwest over the open Atlantic Ocean.

Jeff Masters

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923. azduck
3:03 AM GMT on September 19, 2005
boiredfish - we were pretty much neighbors. CLHS class of 1988!
Member Since: September 7, 2005 Posts: 0 Comments: 57
922. Hawkeyewx
2:16 AM GMT on September 19, 2005
Saint, I spend all day on the computer watching satellite loops, reading discussions, etc... I am 100% hurricane nut.


I looked on WFOR's site but couldn't find anything written by Norcross so I still don't know if he agrees or disagrees with the NHC track south of the keys, but at this point I think Rita will track somewhere from the northern keys to the southern Florida straits. That's a big range and I'm not exactly going out on a limb, but I do think the center will not directly hit the soutern part of the Florida peninsula. I also think the BAM models that now take Rita to New Orleans are not right and the storm will likely move in the vicinity of due west across much of the gulf.
Member Since: July 5, 2005 Posts: 2 Comments: 1924
921. SAINTHURRIFAN
2:11 AM GMT on September 19, 2005
to hawk and 79 thought you would find thi interesting. group of young metrlo. finishing thier dgrees on coast studying katrina
told me today at hospital we were having lunch thier proff. sent them down here to learn more about storms after they hit is where they gain most valuable research not during storm. they were from p.s.u and o.s.u and wisconsin, strange how these midwest schools have to teach us so xcalled coast experts about
storms. ugh p.s.u is where all the accu weather pros are from.
did not want to say much about this because most on here onnly want to experience a storm they informed its the aftermath where they get vital info.noaa also here p.s i rather not say what they think about max mayfield not very flattering lol.
Member Since: August 20, 2005 Posts: 5 Comments: 709
920. stormhank
2:10 AM GMT on September 19, 2005
the bamm models r takin rita toward louisina hope thats not the case
Member Since: September 8, 2005 Posts: 0 Comments: 1386
919. weatherwannabe
2:09 AM GMT on September 19, 2005
see everyone on the next post
918. FSUstormnut
2:08 AM GMT on September 19, 2005
Dr. Masters has a new post!!!
Member Since: June 10, 2005 Posts: 0 Comments: 323
917. Peff
2:07 AM GMT on September 19, 2005
Thanks lefty!....thought you might have gotten tired of the bashing you've been taking, and took a break. Glad to see you're still here! Sure looks weird on radar, but your explanation makes good sense.
915. hurricane79
2:07 AM GMT on September 19, 2005
lakeworth, her wind field has tropical storm force winds 70 miles North of the cEnter, but that can expand as she strengthens.
914. caneman
2:05 AM GMT on September 19, 2005
Link

Hot and hotter..........not good news
Member Since: May 27, 2003 Posts: 14 Comments: 100
913. weatherguy03
2:05 AM GMT on September 19, 2005
I think she may have a southerly component when she nears Florida as the ridge builds in from the North...
Member Since: July 5, 2005 Posts: 592 Comments: 29708
912. tornadoty
2:05 AM GMT on September 19, 2005
Dr. Masters has a new post, and it sounds scary. ~:/
911. weatherwannabe
2:05 AM GMT on September 19, 2005
Nice timimg Peff lol
910. leftyy420
2:04 AM GMT on September 19, 2005
closed cirulation will not split in 2. thats just the high clouds from the 2 strong areas of convection bloing up. basically ur seeing the growth of the cdo
Member Since: August 24, 2005 Posts: 35 Comments: 1987
909. Peff
2:03 AM GMT on September 19, 2005
LOL wannabe :)
908. CosmicEvents
2:02 AM GMT on September 19, 2005
leelee.....WELCOME.
.
.
I don't make predictions, but I feel safe in answering your question. If that is to happen you should expect 30-40MPH winds at most. The only serious but rare possibility would be a tornado. Tornados are quite common on the upper right side of a storm, but the chances of geting hit by one are very slim.
Member Since: August 3, 2005 Posts: 10 Comments: 5680
907. Peff
2:02 AM GMT on September 19, 2005
79...have you seen the last couple of frames of the IR loop for Rita? It almost looks like she's splitting in two (not likely, I know). Do you know if that's ever happenned before?

Thanks

Rita IR Loop
906. weatherwannabe
2:01 AM GMT on September 19, 2005
Rita is looking like a 2 headed monster in the latest IR
905. will40
1:59 AM GMT on September 19, 2005
Hi guys my first post here:-) Dont you think thaat the high pressure north of the Gulf will keep her out of the Centeral Gulf States?
Member Since: September 19, 2005 Posts: 2 Comments: 4266
904. CosmicEvents
1:58 AM GMT on September 19, 2005
Hawkeye....I meant no disrepect. I didn't mean to insult. I also don't look at NHC or Norcross as gods. Nor do I trash them. We agree. I understand and respect your opinion. I think it's smart to only go out 24 hours. As we all know, the further out you go the more error there is. And for the record the NHC and Norcross have both said that there is moderate to strong uncertainty in their forecast beyond 24 hours. Notice who I leave out.
Member Since: August 3, 2005 Posts: 10 Comments: 5680
903. leftyy420
1:58 AM GMT on September 19, 2005
rita will move thru the florida straights. areas as far north as miami could see hurricane condiditons
Member Since: August 24, 2005 Posts: 35 Comments: 1987
902. Lakeworthwx
1:58 AM GMT on September 19, 2005
79 if Rita does go a little north what strength can it reach? Will it stay a tropical storm?
901. leelee75k
1:58 AM GMT on September 19, 2005
longtime lurker, first time poster...
just how big is TS Rita? I'm in West Broward, what should I be expecting if it stays South and passes over the Keys??
Member Since: September 9, 2005 Posts: 0 Comments: 562
900. napleswx
1:57 AM GMT on September 19, 2005
Thanks 79, we didn't see much at all when Katrina went through, like a typical afternoon thunderstorm. Hopefully that will be the case but will keep a close eye on her.
899. SAINTHURRIFAN
1:57 AM GMT on September 19, 2005
soory hawk you are very polite on here just did not want you to
get drug into the trap on this blog that annoys a lot of us a
mateurs bashing experts except the nhc they are infallibe lol.enjoy your input hawk wish you and 79 were the ones on here more often i guess like me your to busy to spend to much time on computer. god bless.
Member Since: August 20, 2005 Posts: 5 Comments: 709
898. FLPanhandle
1:57 AM GMT on September 19, 2005
Hope I don't see Cantore in the FL Panhandle.
897. FSUstormnut
1:55 AM GMT on September 19, 2005
Rita is getting better organized. I didn't realize the winds were up to 50mph already. Any concern for Palm Beach County?
Member Since: June 10, 2005 Posts: 0 Comments: 323
896. hurricane79
1:54 AM GMT on September 19, 2005
Agreed caneman
895. hurricane79
1:54 AM GMT on September 19, 2005
Naples, you should have similar conditions that you had when Katrina moved across South Florida. Winds, some rain, etc. Her center should be crossing over areas near the middle/upper Keys.
894. caneman
1:53 AM GMT on September 19, 2005
I guess its up to mother nature at this point. Wish someone had a crystal ball though :)
Member Since: May 27, 2003 Posts: 14 Comments: 100
893. hurricane79
1:51 AM GMT on September 19, 2005
Sarasota (should) be 100 miles North of Rita. Expect similar conditions that we in Central Florida saw during Katrina, maybe a little breezier. This all could change a little in the next 24 hours though.
892. napleswx
1:51 AM GMT on September 19, 2005
79, if Rita does take the track you are predicting, what effects on SW Florida do you think the storm will have? Since we will be on the northern side as well.
891. taco2me61
1:51 AM GMT on September 19, 2005
Hey all Sebastianjer said it right we all need to wait until it at least gets in the gulf on tuesday, then maybe we will have a better chance on where she is going...
Member Since: July 7, 2005 Posts: 6 Comments: 3261
890. caneman
1:50 AM GMT on September 19, 2005
yech....I hate hurricanes!
Member Since: May 27, 2003 Posts: 14 Comments: 100
889. Hawkeyewx
1:50 AM GMT on September 19, 2005
lefty here i take up for you and your bashing experts again and singing the praises of nhc again i think you should let the experts be experts and the nhc not be god you might catch less flack arrogance is a major pitfall most of us have amateurs that criticize career experts is a sign of jealousy. just a friendly advice that goes to you to hawk.


Saint, why the heck are you including me? All I did was defend myself against a statement I felt was insulting and flat out wrong. I neither worship nor trash any person or agency.

Cosmic, with regard to Norcross I just politely said he was not right if he said the surface center was already at 23N when recon confirmed it was not. I did not hear anything about his forecast for Rita's future track so I couldn't comment on that. I did say the center may be pulled more north, eventually to 23N, by the deepening convection.

For the most part today I have let Lefty, the NHC, Norcross, et al try to figure out exactly where the track would take Rita near the keys. I mostly like to analyze what is going on with the storm in the 0-24 hours span... intensity and short term track/center reformation.
Member Since: July 5, 2005 Posts: 2 Comments: 1924
888. hurricane79
1:50 AM GMT on September 19, 2005
SAINT: on the spot, I would have to give you a range, between Marathon and Homestead. She will not have a Southerly component until she passes Florida.
887. caneman
1:49 AM GMT on September 19, 2005
SAINT, there are hints of the ridge shifting East by 4 to 5 days which will create an opportunity for Rita to have a Northerly component to her movements.

Would this be before 1st landfall in FL or once in the gulf?
Member Since: May 27, 2003 Posts: 14 Comments: 100
886. SRQgal
1:48 AM GMT on September 19, 2005
79..

Based on your current projections for Rita, do you think we in Sarasota need to be 'shuttering'? THX
885. SAINTHURRIFAN
1:48 AM GMT on September 19, 2005
hey ray tampas 2-0 i told you cadillac was a fine ride.
Member Since: August 20, 2005 Posts: 5 Comments: 709
884. caneman
1:48 AM GMT on September 19, 2005
Any new info on Rita?

That's what I'm trying to find out
Member Since: May 27, 2003 Posts: 14 Comments: 100
883. hurricane79
1:47 AM GMT on September 19, 2005
SAINT, there are hints of the ridge shifting East by 4 to 5 days which will create an opportunity for Rita to have a Northerly component to her movements.

Caneman, from what I can see, probable winds between 80 MPH (1) and 100 MPH(2). A lot depends on her forward speed and where, or if she hits.
882. FSUstormnut
1:47 AM GMT on September 19, 2005
Any new info on Rita?
Member Since: June 10, 2005 Posts: 0 Comments: 323
880. SAINTHURRIFAN
1:45 AM GMT on September 19, 2005
i agree lefty and throw the gfs in there with them very interesting the accuracy of the japaneese models not surprised they the masters of electronics lol. ps those models take info
given to them by humans hmm. last time i checked humans are not perfect only one was think he was from bethlehem. 79 on the spot where is final landfal no isodore nonsense i hope.
Member Since: August 20, 2005 Posts: 5 Comments: 709
879. weatherdude65
1:45 AM GMT on September 19, 2005
79...how reliable is the A98E model?
878. 8888888889gg
1:44 AM GMT on September 19, 2005
dos any one no what are the winds like in the P storm right now can some one give me a update on it
877. caneman
1:44 AM GMT on September 19, 2005
It will strike land within 100 miles of Jim Cantore

Don't they all do that? :)
Member Since: May 27, 2003 Posts: 14 Comments: 100
876. weatherguy03
1:44 AM GMT on September 19, 2005
south of the Keys as a CAT2...Then near Houston as a CAT 3..Ok i am putting in my dollar...lol..
Member Since: July 5, 2005 Posts: 592 Comments: 29708
875. sebastianjer
1:44 AM GMT on September 19, 2005
I. believe it or not, agree with wannabe lol
Member Since: August 26, 2005 Posts: 1030 Comments: 11197
874. OBXER
1:43 AM GMT on September 19, 2005
Hey wannabe i graduated with a psych degree so i guess acorsing to you that i can say without a doubt you are a moron
Member Since: September 24, 2001 Posts: 0 Comments: 11
873. weatherguy03
1:43 AM GMT on September 19, 2005
Yeah i'll bet a dollar..ok...
Member Since: July 5, 2005 Posts: 592 Comments: 29708

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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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