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Irene and TD 10

By: Dr. Jeff Masters, 8:17 PM GMT on August 12, 2005

Hello all, I'm back after a long vacation to Yellowstone--a great place to tune into nature and forget the hassles of civilization and your job and just live day-to-day in appreciation of the amazing beauty of a truly extraordinary place. I'll upload a few of my photos and share some reflections of my Yellowstone trip this weekend. It was great to forget about the tropics for a while, but I'm happy to be back to daily blogging as we enter the peak two-month stretch of what has been an already very long hurricane season.

Irene is almost a hurricane. The deep convection at the center of Irene has increased markedly the past few hours, and the first Hurricane Hunter mission into the storm at 2:15pm EDT found an 8 nm wide center with central pressure of 997 mb, and peak surface winds of 70 mph. Irene is over warm 29 - 30C waters, is in a low shear environment, and has good upper-level outflow in all quadrants except the southeast. Irene is sucking in some dry mid-level air from the southeast, which is inhibiting her development some. She is moving to the northwest, which will soon put her in an area of cooler sea surface temperatures (SSTs), left behind by Franklin and Harvey when they churned up these same waters earlier this month. These cooler SSTs should act to keep Irene from rapid intensification, and I expect she will attain Category 1 hurricane status but intensify no further the next two days. Once Irene moves closer to the U.S. coast, there is a narrow area of warmer SSTs along the Gulf Stream that may help intensify her, though. I won't speculate on Irene's track at this point, since steering currents will become weak and Irene may enter a period of erratic motion by Sunday. I'd estimate the chances of Irene getting her name retired by becoming a major hurricane and hitting the U.S. at about 5%. It's pretty rare for a storm this far north to develop into a major hurricane and hit the U.S. Too many things can go wrong--the storm can hit cool SSTs, experience high wind shear, or get recurved out to sea by a fast-moving trough.

Figure 1. Irene's motion to the northwest will soon put her in an area of cooler SSTs left behind by Franklin and Harvey. However, the tropical disturbance at 12N 43W was plenty of warm water in front of it as it moves WNW at 10-15 mph. Image credit: U.S. Navy.

TD 10?
The system that might have a greater chance of developing into a serious threat lies in the middle tropical Atlantic near 12N 43W. A closed low pressure with central pressure of 1012 mb has developed here from a tropical wave, and although convection has declined a bit this afternoon, this system has an excellent chance of becoming TD 10 this weekend. Buoys in the vicinity already report winds of 20-25 knots, and the low lies in an area of light wind shear and warm waters (28 - 29C), with plenty of warm water in front of it as it moves WNW at 10-15 mph. The low is far enough south to avoid entraining in some dry Saharan air that lies to the north.

Jeff Masters

The views of the author are his/her own and do not necessarily represent the position of The Weather Company or its parent, IBM.

Reader Comments

welcome back jeff how was your trip
so jeff its possable that the low will develop into a depression. does it have the potential of becoming a hurricane like that of emily or dennis.
Welcome back Jeff. On TD10?, is there any early model guidance? Also, do you have an opinion on steering patterns once it gets through the Windwards?
Jeff, I think he answered all of your questions already. He said he was going to post about his trip sometime this weekend. He said the low was probably going to be a depression. Too early for anyone to say if it will be a hurricane or not.
How will the high influence this wave/TD 10. Could it steer toward the US East Coast?
Wow, look at the SSTs in the Bahamas and on the west coast of Florida. I think it's safe to say that a storm following the path of Charley or Frances/Jeanne is going to have quite an energy base to work from.
Yes, pretty warm.
Early model runs have the wave moving quickly to the north, eventually tracking right behind Irene. However, model runs coming out of a system that hasnt even developed yet are usually very poor.

Looks like we might have a hurricane at 11pm, if not an 80mph hurricane. This storm is finally proving to be worth declaring it a depression a long long time ago. I am sure the NHC is happy to see it become a storm, considering it fell apart so quickly after they declared it a depression.
It is well into the 90s that would be hot not warm at times warmer then the landmasses up to 95 which siriously scares me because that is how hot some areas near florida the bahamas and the caribean are.about 90% of gulf is 90 right now.....
Yes winds are 70 mph now indcated by recon flight.
Jeff, are you sure you meant 8 nm and not 80 nm for the eyewall radius?
I am suspicious about this norwest movement because they never show a movement if they believe its a jog which this due westerly movent could be but loook at th track the past several hours have had it moving due west it could just be a jog and that why the NHC is still saying northwest but I think thats a bit much and cearly isn't moving northwest for the sort term at most west north west.
no I heard it was 30 miles wide its not 8 miles thats too small based on satelite.
yes jed you are right 30 mile wide eye but its bound to shrink because its tightening up now...look for a major slow down and a stall for at least 24 hours...no one is out the woods on this one...the high could strengthen and really cause problems later for florida....they need to pay attention..
ill be back at around midnight with another update after i look at the new data coming in....
jed the storm has definitely been moving on a due west heading for the last 4 hours..i dont know why the nhc has it moving nw..if this storm slows to a crawl like i expect it to do you are going to see the nhc changing all kinds of predictions...btw i expect it to become a hurricane in the next advisory 80mph winds...
17. WSI
Stormtop, I am still curious which model is taking Irene over Bermuda. You never have answered me yet. You said one of the models was taking Irene right over Bermuda. I can't seem to find which one you are talking about. Thanks.
18. SEFL
I am sad to discover that we cannot believe any of the data produced by the hunter aircraft. I guess we all just need to wait for Stormtop's next update.
19. deb1
The models have been curving this storm out to see ever since it came into being. It doesn't look to me like it is moving NW right now; WNW at the most, maybe even due west.
20. deb1
21. SEFL

At the current position the models have the storm moving wnw to nw. I think at 5 pm they said motion was 310 which is slightly west of northwest. So it seems you have discovered it is moving in the expected direction.
I live in Jupiter, FL (Northeasternmost Palm Beach County). Should I be wary of a direct hit from Irene?
Looking at the latest sat., it does look like a wnw direction for now.Last couple of frames seems to show some intensification.
bextreme, I would not worry yet, just keep an eye on it.
25. SEFL
bxtreme, imho, no.
Thats what I am doing, I live on the southeast coast of NC.
27. deb1
Sefl, my point about the models was that various ones of them have been predicting a turn to the north and out to sea within 5 days, prior to this storm actually making such a turn, ever since it started. Regardless of whether its exact current track is W, WNW or NW,, who is to say the storm will turn north and out to sea as soon as the models predict? So far they have got it wrong.
28. SEFL
what have they gotten wrong? anhd I dont understand what you mean when you say "who is to say the storm will... Thats the nhc's job, to use available information and predict storm tracks. Give all of us an idea what to expect from the unexpected. Are you expecting perfection from these forecasts from day One? I guess in the end it is up to the storm where it will go, but she isn't talking.
Jeff isn't talking about Irene anymore so that says something in it's self right there that no one expects Irene to hit land.
one more time this storm is not going out to sea...the high pressure is strengthing and the mb is 610 right now....the pressure and the middle level low combined to the south in the winward islands will slow the storm down to a crawl...once the storm slows you will be able to see a dramatic shift to the west in motion and the winds will increase to hurricane force...the areas affected will bbe the areas from miami to the s and n carolina borders...this storm is increasing in strength and size...this storm will sTALL OFF THE COAST OF THE SE US FOR 24 HOURS AND INCREASE IN STRENGTH WHILE THE INNER CORE BECOMES MORE CONCENTRATED AND MORE ORGANIZED...I STILL CANT SEE HOw THE NHC HAS THE STORM MOVING NW......I HAVE SEEN A WEST MOVENENT FOR THE LAST 12 HOURS....WHAT IS GOING ON WITH THE NHC POSITION...I THINK PEOPLE ALONG THE FLORIDA COAST SHOULD BE ALERT TO TAKE QUICK ACTION IF THE HIGH PRESSURE STRENGTHENS TO 600 MB AND THAT IN ITSELF ...