Leslie headed towards Bermuda; Tropical Storm Michael forms

By: Dr. Jeff Masters , 3:01 PM GMT on September 04, 2012

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Tropical Storm Leslie continues to suffer from moderately high wind shear of 15 - 20 knots, due to strong upper-level winds out of the northwest. The shear is keeping heavy thunderstorms confined to the southeast quadrant of the storm. Satellite loops show that Leslie has almost no heavy thunderstorm activity near its center, and the storm is crawling north at walking pace, 3 mph. Leslie's slow forward speed means that the storm is staying over the cold water stirred up by the storm's winds, inhibiting intensification. According to the latest SHIPS model forecast, the shear is expected to stay moderately high through Tuesday night, then drop to the low category, 5 - 10 knots, by Thursday afternoon. At that time, Leslie will be over warm ocean waters of 29 - 30°C, and the reduction in shear and warm waters should aid intensification. However, Leslie's motion will continue to be slow, keeping the storm over its cool water wake, and keeping any intensification slow. Once Leslie begins moving more quickly on Saturday, this effect will diminish, and Leslie could be at Category 2 strength on Sunday morning, as indicated in the official NHC forecast. Steering currents for Leslie are expected to be weak through Friday, as Leslie is stuck between two upper level lows. The latest guidance from our top computer models continues to show Leslie making a very close pass by Bermuda on Saturday. Leslie is a huge storm, and tropical storm-force winds are expected to extend outward from its center 250 miles by Friday. Bermuda is likely to see a 48-hour period of tropical storm-force winds beginning Friday night that lasts until Sunday night. The official NHC forecast shows Leslie nearly making a direct hit on Bermuda, but the uncertainty in 4-day NHC forecasts is around 200 miles. Thus, the latest 11 am EDT NHC wind probability forecast calls for just a 12% chance of hurricane force winds on Bermuda on Saturday. Nevertheless, Leslie is capable of bringing an extended period of hurricane-force winds lasting six or more hours to Bermuda Saturday night through Sunday morning, should a direct hit materialize.


Figure 1. Morning satellite image of Tropical Storm Leslie. The low-level circulation center has very little in the way of heavy thunderstorms surrounding it, thanks to strong northwest winds creating 15 - 20 knots of wind shear.

Leslie will stay stuck in a weak steering current environment until a strong trough of low pressure approaches the U.S. East Coast on Saturday. This trough should be strong enough to pull Leslie quickly to the north on Saturday and Sunday, and Leslie may be close enough to the coast that the storm will make landfall in Nova Scotia or Newfoundland, Canada on Monday, September 10. None of the reliable models have shown that a direct hit on New England will occur, but we can't rule that possibility out yet. The storm may also miss land entirely, and brush by the coasts of Nova Scotia and Newfoundland. Large swells from Leslie reached Cape Hatteras, North Carolina last night, and will begin pounding the entire Eastern Seaboard today through Sunday. These waves will be capable of causing significant beach erosion and dangerous rip currents. The Hurricane Hunters are scheduled to make their first flight into Leslie on Wednesday afternoon.


Figure 2. Morning satellite image of Tropical Storm Michael.

Tropical Storm Michael forms in the Central Atlantic
Tropical Storm Michael has formed in the Central Atlantic on Monday, but is not destined for fame. Satellite loops show that this is a very small tropical cyclone, and the storm is well away from any land areas. Michael is under moderately high shear of 15 - 20 knots, and this shear is forecast to remain at 15 - 20 knots through Wednesday. Since Michael is such a small storm, just a modest increase in shear could destroy it. But if Michael survives until Thursday, when shear is expected to fall to the low range, it has the opportunity to strengthen.

Michaels's formation on September 4 puts 2012 in third place for earliest formation date of the season's thirteenth storm. The record is held jointly by 2005, which had Hurricane Maria form on September 2, and 2011, which had Tropical Storm Lee form on September 2 (there was an unnamed tropical storm that year before Lee.) None of the models show that Michael will threaten any land areas. Michael is a classic example of the type of storm that likely would have been missed before the advent of satellites, since the storm is small, far from land, and may be short-lived.

Jeff Masters

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Quoting hunkerdown:

what is your issue with the "." between each word???

Also, who is Issacc?? Come on, how hard is it to spell these names correctly...you aren't even close.


He does that all the time. I think it's his meme or something....or he just likes to be annoying. So far, he's batting about .100 with posts that make any sense.
Member Since: October 2, 2004 Posts: 0 Comments: 16207
Well have a goodnight all, you would have to seriously pay me to stay up and wait for the Euro to update.
Member Since: August 31, 2009 Posts: 0 Comments: 5628
Quoting GTcooliebai:
Actually Sar you might not believe me, but it was the VIPIR model that nailed Charley's track over Punta Gorda when all the other models insisted that he was coming up towards Tampa Bay. I remember watching coverage of Charley on WFLA news channel 8. Now mind you this was in 2004 and the prospects of a hurricane coming out of this little feature that has emerged into the GOM aren't very high. I really would like to see a link to this model if they have one.


Yeah, I know it does a fairly good job with actual storms. I haven't seen it does such a good job with blobs. :)
Member Since: October 2, 2004 Posts: 0 Comments: 16207
GFDL is in line with the HWRF and shows a direct hit on Bermuda, maybe that is a good thing it shows it now, since you know the saying models point to you this far out, they will likely point somewhere else:

Member Since: August 31, 2009 Posts: 0 Comments: 5628
Quoting Grothar:


I bet Morse Code would drive you to distraction. j/k


Hey, I'm a ham radio operator, and I know Morse Code.
--. .-. --- - .... .- - .. ... --- .-.. -.. . .-. - .... .- -. -.. .. .-. -

Member Since: October 2, 2004 Posts: 0 Comments: 16207
Quoting sar2401:


I hope the VIPIR is good at eating crow. :)
Actually Sar you might not believe me, but it was the VIPIR model that nailed Charley's track over Punta Gorda when all the other models insisted that he was coming up towards Tampa Bay. I remember watching coverage of Charley on WFLA news channel 8. Now mind you this was in 2004 and the prospects of a hurricane coming out of this little feature that has emerged into the GOM aren't very high. I really would like to see a link to this model if they have one.
Member Since: August 31, 2009 Posts: 0 Comments: 5628
Quoting trHUrrIXC5MMX:


let me call my tow truck...lol


LOL...you need some of those big Russian salvage tugs.
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Quoting leftlink:



140mph, or 121.7 kts was the number provided by RTSplayer. You are right it was erronous, but unfortunately the NHC did not bother to update its archive material with any disclaimer: http://www.nhc.noaa.gov/archive/storm_wallets/atla ntic/atl1992/andrew/public/pal0492.033

If you are concerned about misinformation getting spread, then maybe it would be a good idea for some of your ire to be directed at the NHC so that we can convince them to put a big asterisk next to that 140mph number.

I updated my original post to use 165mph, or 143.4 kts. Which does not change my argument... that to provide ADVANCE WARNING about a storm prior to landfall, the system of only using wind speed to determine intensity level is broken.

What kind of change to the warning system would prevent the nhc from under-reporting the danger of a future Andrew?


Holy cow, are you guys still at it? Don't you have to go to work or school in the morning? You're both going to be all grumpy. :)
Member Since: October 2, 2004 Posts: 0 Comments: 16207
Quoting sar2401:


Won't happen unless Bermuda moves about 100 miles west. :)


let me call my tow truck...lol
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Quoting GTcooliebai:
I don't know the intensity might be overdone, as far as track goes it has been fairly consistent for days on taking it rather close to Bermuda, but you are right it wouldn't take much for them to be spared the worst weather, since there is still a fairly good margin of error out to 4 days and they are an island after all.

The models do take it west a little bit west on each run. Just running some quick numbers, if that trend continues, Leslie passes about 100 miles west of Bermuda. Now, if Leslie is still that huge, that puts Bermuda on the tough side of the storm, so it won't be a day at the beach. OTOH, if she stays that huge, it's hard to see her getting abve a cat 1, so it could be worse. I think Nova Scotia is her eventual target.
Member Since: October 2, 2004 Posts: 0 Comments: 16207
Quoting hunkerdown:

Where do you get Andrew's wind speed at landfall as 121.7??



140mph, or 121.7 kts was the number provided by korintheman. You are right it was erronous, but unfortunately the NHC did not bother to update its archive material with any disclaimer: http://www.nhc.noaa.gov/archive/storm_wallets/atla ntic/atl1992/andrew/public/pal0492.033

If you are concerned about misinformation getting spread, then maybe it would be a good idea for some of your ire to be directed at the NHC so that we can convince them to put a big asterisk next to that 140mph number.

I updated my original post to use 165mph, or 143.4 kts. Which does not change my argument... that to provide ADVANCE WARNING about a storm prior to landfall, the system of only using wind speed to determine intensity level is broken.

What kind of change to the warning system would prevent the nhc from under-reporting the danger of a future Andrew?
Member Since: December 28, 2010 Posts: 0 Comments: 134
Quoting louisianaweatherguy:
Bob Breck (New Orleans Fox8 weather) showed VIPIR model picking up on the blob drifting into the gulf turning into a TS/Hurr and going into Tampa Bay this weekend... interesting...

...KEEP IN MIND that the VIPIR model has been very much correct for most of the season (including Debby from the very beginning)


I hope the VIPIR is good at eating crow. :)
Member Since: October 2, 2004 Posts: 0 Comments: 16207
Quoting sar2401:


Won't happen unless Bermuda moves about 100 miles west. :)
I don't know the intensity might be overdone, as far as track goes it has been fairly consistent for days on taking it rather close to Bermuda, but you are right it wouldn't take much for them to be spared the worst weather, since there is still a fairly good margin of error out to 4 days and they are an island after all.
Member Since: August 31, 2009 Posts: 0 Comments: 5628
Sept. 4 ENSO update from the CPC sez:

"The atmospheric circulation over the tropical Pacific is near average."
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Quoting 7544:
hmmm might see xisaac blow up in the gulf tonight stay tuned


He sure don't look like much tonight as far as I can see. Something exciting is going to have to happen in the next 6 hours or so.
Member Since: October 2, 2004 Posts: 0 Comments: 16207
Quoting garlicbulb:
What about TS John and its effects on California?


John is a big thief...totally just stole the name. worthless 40 mph storm...
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Quoting GTcooliebai:
Oh no this would be bad, the HWRF places Leslie right on top of Bermuda in 102 hrs.


I know..by presssure its a cat 4... but take the size into account...maybe 110 - 125 mph.

remember Isaac an 80 mph with a cat 2 pressure of 968?
still very bad for Bermuda
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Quoting GTcooliebai:
Oh no this would be bad, the HWRF places Leslie right on top of Bermuda in 102 hrs.



Won't happen unless Bermuda moves about 100 miles west. :)
Member Since: October 2, 2004 Posts: 0 Comments: 16207
Quoting garlicbulb:
What about TS John and its effects on California?


John is officially dead as a tropical storm. The remnant low may head for southern California in about 4-5 days. The biggest worry would be dry lightning, starting wildfires.
Member Since: October 2, 2004 Posts: 0 Comments: 16207
Oh no this would be bad, the HWRF places Leslie right on top of Bermuda in 102 hrs. Don't freak out though, HWRF usually overdoes the intensity, not sure how well it does on track, but I notice it usually follows suite with the GFS and GFDL.

Member Since: August 31, 2009 Posts: 0 Comments: 5628
917. LBAR
Leslie's far outer debris clouds and outflow are starting to squish little Michael. He's holding his own, though!

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Quoting garlicbulb:
What about TS John and its effects on California?


I live in Soo Cal.......nada effect so far...maybe a bit of surf...thought it dissipated.
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I´m out
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Quoting Stoopid1:
Leslie's appearance has improved a good bit this morning.


indeed it has
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What about TS John and its effects on California?
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Leslie's appearance has improved a good bit this morning.
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Quoting Grothar:


I bet Morse Code would drive you to distraction. j/k


Do they still call that Diddy Bop?
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The clouds pattern is starting to seem like a Hurricane
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I am off to read a nice bedtime story before I enter the realm of dreams: Everything Won't Be Alright.
Now it's time to say Good Night.
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908. 7544
hmmm might see xisaac blow up in the gulf tonight stay tuned
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Leslie looking better all the time..
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Quoting Gearsts:
The wave off the coast of Africa.
Yeah I know I'm agreeing with you :)
Member Since: August 31, 2009 Posts: 0 Comments: 5628
Quoting GTcooliebai:
Uh huh...By the way it looks like our friend Leslie is trying to clear out an eye:

The wave off the coast of Africa.
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Quoting Xyrus2000:

In summary, every piece of scientific data goes against your claim.
They do not care, it is part of their religion. Their belief trumps all facts and alters reality and the entire physical universe.
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903. Skyepony (Mod)
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Quoting Gearsts:
Thats the big boy that we need to watch?
Uh huh...By the way it looks like our friend Leslie is trying to clear out an eye:

Member Since: August 31, 2009 Posts: 0 Comments: 5628
Quoting Gearsts:
Thats the big boy that we need to watch?


Yup!!!
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Leslie is trying to wink at us.


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Quoting GTcooliebai:
Shortwave Eastern Atlantic:

Thats the big boy that we need to watch?
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Shortwave Eastern Atlantic:

Member Since: August 31, 2009 Posts: 0 Comments: 5628
360 hrs.

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Quoting stormchaser19:
288 hr


keep em' coming!
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288 hr
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252 hr
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216 hr
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892. 7544
hmm whatever is moving south into the gulf has some good banding to it on the south side looks like its a half of a strom at this hour
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168 hr
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Quoting stormchaser19:
150 hr
Leslie makes landfall in New Foundland and new system in the Central Atlantic.
Member Since: August 31, 2009 Posts: 0 Comments: 5628
Quoting NoloContendere:
Not to worry, it's been lower than that even in my lifetime. I can remember when the submarine Skate surfaced at the North Pole in 1958. If you want to worry about something, worry about global cooling and whether we're heading for a Dalton or Maunder type solar minimum. Think cold.



Subs are capable of breaking through up to 25 feet of ice if necessary. Not only that, but there are natural fissures and cracks that form even in the heart of arctic night due to wind and ocean currents.

You won't find 1958 naval maps with the kind of ice extent we are seeing. Or any other historical surface naval maps either. In recorded naval history going back as far as the 1600's, the ice extent has never been anywhere near the current levels. Never. Period.

To further the point, the last time ice extent was this low according to climatological proxies was around 125,000 years ago. Sea levels were much higher, and the world was quite a different place, climatologically speaking. Modern man had just barely arrived on the scene.

Basic physics do not back up any hypothetical global cooling. Short of a massive volcanic event, the planet will continue to warm, regardless of a Maunder minimum (greenhouse climate forcings exceed that of any solar minimum). We are already seeing the effects from the reduced ice. The unprecedented polar "hurricane" that formed this year from all that open water in the arctic was just one example. The warming arctic is also having an effect on global weather patterns, which Dr. M has discussed in several of hist postings.

In summary, every piece of scientific data goes against your claim.
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I can't believe how huge the last advisory has Leslie being. Tropical storm force winds extend up to 230 miles from the center of the storm... that's a whopping 50 miles bigger than Isaac was at maximum intensity.

The Atlantic basin seems to have an unnatural propensity for producing really gigantic hurricanes these past few years. It seems like every single one has a gale diameter over 400 miles wide.
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150 hr
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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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