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Disorganized Leslie headed towards Bermuda

By: Dr. Jeff Masters , 4:18 PM GMT on September 03, 2012

Tropical Storm Leslie continues to struggle with 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. These thunderstorms are as far removed from the center as we've so far with Leslie, as seen on satellite loops. 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 Wednesday night. At that time, Leslie will be over warm ocean waters of 29°C, and the reduction in shear and warm waters should allow Leslie to intensify into at least a Category 1 hurricane by Friday, as predicted by most of the intensity forecast models. Intensification to a stronger storm may be hampered by its slow motion, which will cause Leslie to churn up cool water from the depths that will slow intensification. Once Leslie begins moving more quickly on Saturday, this effect will diminish, and Leslie could be at Category 2 strength on Saturday, as predicted by the HWRF and LGEM models. Steering currents for Leslie are expected to be weak on Tuesday - Friday, as Leslie gets stuck between two upper level lows. The latest guidance from our top computer continues to show Leslie making a very close pass by Bermuda on Saturday, and that island can expect a 3-day period of rough weather Friday through Sunday. 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 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 most likely long-term fate of Leslie will be for it to miss land entirely and brush by the coasts of Nova Scotia and Newfoundland, but any forecast of what a tropical cyclone might do a full seven days in advance is pretty speculative. Regardless, Leslie will bring an extended period of high waves to Bermuda, the U.S. East Coast, and Nova Scotia and Newfoundland this week. These waves will be capable of causing significant beach erosion and dangerous rip currents.


Figure 1. Morning satellite image of Tropical Storm Leslie. The low-level circulation center is fully exposed to view, thanks to strong northwest winds creating 15 - 20 knots of wind shear.

Invest 99L in the Central Atlantic
A small extratropical low pressure system that got cut off from the jet stream and is now spinning away in the Central Atlantic, near 26°N 42°W, (Invest 99L), is headed west at 10 mph, and has developed a small amount of heavy thunderstorm activity. This storm is not a threat to any land areas, and in their 8 am EDT Tropical Weather Outlook on Monday, NHC gave 99L a 30% chance of developing into a tropical cyclone by Wednesday morning.

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

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472. superpete
Quoting stormpetrol:
I wonder if 12N/33W will get a yellow circle at 8pm, it looks better than TD13.


Hi Stormpetrol
I was wondering the same thing until I read todays NHC 2 pm discussion,they mention 'no cyclonic signature associated with the wave, embedded in the monsoon trough' to this effect......
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471. beell
Isaac still has a broad and weak presence over the SE.
It may mingle with the eastern FL ULL at some point.

Current RAP 700mb


And the SPC mentioned a cast-off remnant circulation from Issac earlier this afternoon. It was visible on Atlanta radar for a while. Not much left to it now.

This afternoon's convection is a result of westerly/southwesterly flow around the Isaac-trough and southeasterlies/seabreeze. Confluent/convergent flow.


DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0246 PM CDT MON SEP 03 2012

...FARTHER NORTH...SEVERAL BANDS OF BROKEN CONVECTION HAVE EVOLVED FROM GA INTO THE CAROLINAS. RADAR DATA SUGGESTS A WEAK MCV MAY BE EMBEDDED OVER NCNTRL GA AND THIS MAY ENCOURAGE UPWARD GROWTH OF BROKEN LINE SEGMENTS DOWNSTREAM AS THIS FEATURE LIFTS NEWD INTO NRN SC...
Member Since: December 31, 1969 Posts: Comments:
470. mitthbevnuruodo
Quoting CybrTeddy:
12z ECMWF. Leslie becomes a monster Category 5, Michael from TD13, develops a TD or weak TS in the Gulf by 96 hours, and two very well organized tropical waves, one of which develops into another tropical storm. Nadine and Oscar respectively.

Good lord though, this is one of those times the Euro can way overbomb intensity forecasts. Brings Leslie all the way down to 914mb approaching New England. That would be nuts.




I have to admit, I'd be a bit...ok, alot...surprised if Leslie ended up cat5, or even a cat4. I really have a hard time seeing it bomb out THAT much. IMO, it just doesn't look like the conditions are set good enough for all that.
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469. ncstorm




this looks like the Atlantic Ocean blew up
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468. RTSplayer
Quoting CaicosRetiredSailor:
How Low can Leslie Go?


Map says sub-880 is possible, but highly, highly unlikely.

It would be incredibly explosive intensification to pull that one off.
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467. windshear1993

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466. GeoffreyWPB
The end of a nice 10-hour work day!

Tropics are heating up...Interesting to see if the remnants of Isaac make it back to the GOM..
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465. GTcooliebai
966 mb. 108 hrs.
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464. TampaWeatherBuff
Quoting CybrTeddy:
Brings Leslie all the way down to 914mb approaching New England. That would be nuts.


Indeed. I doubt the data is quite that high in octane. Methinks that model better lay off the Red Bull for the next run.
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463. CybrTeddy
ECMWF wants to make Leslie a Category 2 by 48 hours. Things would really have to turn around for it by then. Though, it has been decreasing throughout the day.

00z.


21z
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462. TropicalAnalystwx13
Quoting Tazmanian:
LOL


from wikipedia


what you guys see here



Tropical Depression Thirteen


Current storm information

As of 5 p.m. EDT (2100 UTC) September 2, Tropical Storm Leslie is located within 30 nautical miles of 25.6°N 42.2°W, about 1350 mi (2170 km) WNW of the Cape Verde Islands. Maximum sustained winds are 30 knots (35 mph, 55 km/h), with stronger gusts. Minimum central pressure is 1012 mbar (hPa; 29.88 InHg), and the system is moving northwest at 3 kt (3 mph, 6 km/h)

I fixed it, Taz. We get busy trying to update the ACE page, timeline, timeline page, current storm information section, and even articles (when one is warranted). Just bare with us...any mistakes you guys see will be corrected promptly.
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461. RTSplayer
Quoting CybrTeddy:
12z ECMWF. Leslie becomes a monster Category 5, Michael from TD13, develops a TD or weak TS in the Gulf by 96 hours, and two very well organized tropical waves, one of which develops into another tropical storm. Nadine and Oscar respectively.

Good lord though, this is one of those times the Euro can way overbomb intensity forecasts. Brings Leslie all the way down to 914mb approaching New England. That would be nuts.





Look at that...

The 1004mb pressure extends half way into N. Carolina and Virginia.

Still a category 4 passing New Jersey, with 1008mb (stronger than TD13) pressure still extending into Georgia...


If this verifies, it would like double the year's ACE value in one storm, because this isn't just a "little" cat 5, it's a monster...
Member Since: December 31, 1969 Posts: Comments:
460. ncstorm
Quoting Grothar:
Ineresting change in coordinates, a little shift to the west.

23.5N 62.0W - 006z
24.1N 62.8W - 012z
23.8N 63.1W - 018z


how close you think this can get to the CONUS from the midatlantic northwards...I dont like the Euro having the center passing west of Bermuda now..
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459. wxchaser97
Quoting WeatherNerdPR:
I'm not sure, but I think the ECMWF may be over-doing the intensity a little. ;P

Lets all hope so because if the Euro is right then, bye bye Bermuda.
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458. Tazmanian
LOL


from wikipedia


what you guys see here



Tropical Depression Thirteen


Current storm information

As of 5 p.m. EDT (2100 UTC) September 2, Tropical Storm Leslie is located within 30 nautical miles of 25.6°N 42.2°W, about 1350 mi (2170 km) WNW of the Cape Verde Islands. Maximum sustained winds are 30 knots (35 mph, 55 km/h), with stronger gusts. Minimum central pressure is 1012 mbar (hPa; 29.88 InHg), and the system is moving northwest at 3 kt (3 mph, 6 km/h)
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457. aspectre
164 aislinnpaps: Why do hurricanes always want to land at night?

Cuz they're cheap. If they hit the beaches during the day, they'd hafta buy sun tan lotion.
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456. HurricaneHunterJoe
Quoting Grothar:
Ineresting change in coordinates, a little shift to the west.

23.5N 62.0W - 006z
24.1N 62.8W - 012z
23.8N 63.1W - 018z


Any blatant implications from that Most Wise One?
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455. stormchaser19
Quoting yqt1001:


Yeah, you don't see those often, if ever. Especially on the more reliable models.



Especially with the European for me is one of the most conservative model in intensity
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454. CaicosRetiredSailor
How Low can Leslie Go?
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453. windshear1993
Quoting trHUrrIXC5MMX:


what??????

can Leslie go so extremely far??
dont forget what hurricane dog in 1950 did and it was far north
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452. GTcooliebai
I guess it is just inevitable now that Leslie becomes the first major hurricane of the season and look where it's heading towards Bermuda...sad.
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451. Grothar
Ineresting change in coordinates, a little shift to the west.

23.5N 62.0W - 006z
24.1N 62.8W - 012z
23.8N 63.1W - 018z
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450. TropicalAnalystwx13
At the very least, adjusting for Leslie's large size, the ECMWF shows a strong Category 4 hurricane. Still a very powerful and dangerous hurricane, not only for Bermuda in terms of direct impacts (rain and wind), but the entire East Coast for indirect impacts (beach erosion, rip currents, etc).
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449. WeatherNerdPR
I'm not sure, but I think the ECMWF may be over-doing the intensity a little. ;P
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448. stormpetrol
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447. Tazmanian
Quoting CybrTeddy:
12z ECMWF. Leslie becomes a monster Category 5, Michael from TD13, develops a TD or weak TS in the Gulf by 96 hours, and two very well organized tropical waves, one of which develops into another tropical storm.

Good lord though, this is one of those times the Euro can way overbomb intensity forecasts. Brings Leslie all the way down to 914mb approaching New England. That would be nuts.





poor New England.
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446. RTSplayer
Quoting TropicalAnalystwx13:

914 millibars.



That's peak intensity, not closest approach.


Still, with the 5mb initialization error adjustment that's down to 909mb, potentially.

I have 911mb adjusted intensity for closest approach now on the Euro...
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445. stormpetrol
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444. CybrTeddy
12z ECMWF. Leslie becomes a monster Category 5, Michael from TD13, develops a TD or weak TS in the Gulf by 96 hours, and two very well organized tropical waves, one of which develops into another tropical storm. Nadine and Oscar respectively.

Good lord though, this is one of those times the Euro can way overbomb intensity forecasts. Brings Leslie all the way down to 914mb approaching New England. That would be nuts.
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443. yqt1001
Quoting TropicalAnalystwx13:
My second reaction: That's a Category 5 on a model if I've ever seen one.


Yeah, you don't see those often, if ever. Especially on the more reliable models.
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442. barbamz
Quoting Grothar:


I was reading up on this earlier. It doesn't seem to be as bad as they thought, but still very strong.


Right, Gro. Next week I'll check the situation at the Med personally when I go to Italy for vacation (Toscana). But before that of course I dare to see what will happen with Leslie.
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441. KEEPEROFTHEGATE (Mod)
Quoting MahFL:


A Cat2 won't do much to Bermuda, they have very strict building codes.


all buildings made of stone cat 4 or greater to destroy stone
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440. trHUrrIXC5MMX
Quoting TropicalAnalystwx13:

914 millibars.



what??????

can Leslie go so extremely far??
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439. TropicalAnalystwx13
My second reaction: That's a Category 5 on a model if I've ever seen one.
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438. RTSplayer
Quoting stormchaser19:

Cat 5


Crap..

What the heck? How did I miss that?

I clearly mis-read the map when I was doing my adjusted intensity forecast.

You gotta be kidding me?!

That has 916mb right on Bermuda, and it needs a -5mb adjustment to account for the bad initialization.


The water temps cleary support it since it's going to be passing over a broad 30C to 31C SST region.



Conditions south of Bermuda easily favor that in terms of water temps and upper atmosphere temps.

Even if you adjusted the potential intensity map UP by 20mb, it would still be well within possibility.

The max wind predictor is 2 color scales above the "borderline/low end cat 5" zone as well.

I don't know what I was doing above, but I need to fix my numbers.
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437. wxmod
Quoting RTSplayer:
AGW...





I calculated complete summer meltdown in 8 to 14 years.*

Complete winter meltdown in 36 years**.

* This uses only the exponential regression of Area. A better method would be to "squeeze" the regressions of Area, volume, and extent to be equal to zero in the same year, or within a 95% confidence of the same year...because the shape of the ice is amorphous, there is not a 1 to 1 correlation to the graphs in any one year, however, whenever volume reaches zero, all other values must be zero by the squeeze theorem.


** There is a negative feedback effect which could delay this a few more decades, its hard to quantify from the available data.


The rate of decrease in winter maximum is currently increasing at an exponential rate of 50% per 7 years, or 5.96% per year.

The rate of increase in annual net melting for the Summer minimum is currently increasing between 50% and 100% per five years. For this year, it is hard to tell, since the trend line says 50% per 5 years for the past 5 years, but this year's actual data point suggests 100%, just as was the case for the past 20 years. This is somewhere between an exponential trend of 8.447% per year and 14.87% per year.


This stuff doesn't matter. Fact is: Arctic ice VOLUME has been decimated. Your calculations only obscure that fact.
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436. trHUrrIXC5MMX
Quoting TropicalAnalystwx13:
I just looked at the 12z ECMWF.

My first reaction: Holy freaking crap!



WOW!!!!!!!!!! 917MB!!!!!!!!!!??
HOLLY COW!!!!!!

That's a major Cat 5!!!! I think that model is malfunctioning... lol


Nice Med storm... these are becoming more frequent lately...
It would be cool for an organization to track these storm like our NHC...
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435. GTcooliebai
Quoting Tazmanian:


if we get Michael from TD 13


that would mean we get Nadine,Oscar,Patty ,Rafael,Sandy



if i did it right
Could make a run at the Greek letters, but lets not get ahead of ourselves.
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434. Tazmanian
Quoting HurricaneDean07:

Also.
5 Named storms in that image.


if we get Michael from TD 13


that would mean we get Nadine,Oscar,Patty ,Rafael,Sandy



if i did it right
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433. ncstorm
914 mb from the Euro right at Bermuda..I like Allan's graphics better..the black really gives a doom and gloom scenario
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432. Hurricanes101
Quoting stormpetrol:
I wonder if 12N/33W will get a yellow circle at 8pm, it looks better than TD13.


looks can be deceiving, dont be fooled by the convection
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431. wxchaser97
Quoting TropicalAnalystwx13:
I just looked at the 12z ECMWF.

My first reaction: Holy freaking crap!


Holy bleep bleep, cat5. That would be crazy, well it is peak season. Bermuda would have a bad time if the Euro came true.
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430. WeatherNerdPR
Quoting wxgeek723:


Jeez dude I acknowledge that you're right and give in to your argument and you still nag at me? Am I not entitled to my own opinion?

Sorry for sounding like a jerk, it's just the way you wrote it made it look like you still were denying it (read:"sad clump of thunderstorms"). Of course you are entitled to your own opinion, but I still disagree with you on your remark regarding Helene. ;)

Quoting wxgeek723:


And when I mean a name is special I mean tropical cyclones are special for being named.

Interesting perspective. I guess you could say that tropical cyclones are a tier above other atmospheric disturbances. If that was you were trying to portray, you're right.


Quoting wxgeek723:


You are right though. I thought about it and I should not try and defy the choices that the NWS/NHC/SPC/etc make, and the systems this year have been legit. This year is better than 2007 though, some of those storms looked like open waves with names. I still maintain the NHC pulls fast ones with storms sometimes, and no offense but I think it's a bit ignorant to go by this 'NHC decisions are infallible' mentality.

Yeah, I wouldn't regard the NHC as infallible (Igor not a Cat 5 grr), but you must recognize that they know more than you. Sometimes your comments make it sound like you have the "NHC is wrong and I'm right" mentality, but I digress.

Good to see that this discussion didn't end with us screaming "POOF!" at each other. :P
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429. TropicalAnalystwx13
Quoting HurricaneDean07:

917 MB?!

914 millibars.
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428. stormpetrol
I wonder if 12N/33W will get a yellow circle at 8pm, it looks better than TD13.
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427. MahFL
Quoting TropicalAnalystwx13:
I feel bad for Bermuda. They'll be in the right front quadrant of what should be a Category 2 hurricane.



A Cat2 won't do much to Bermuda, they have very strict building codes.
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426. HurricaneDean07
Quoting HurricaneDean07:

917 MB?!

Also.
5 Named storms in that image.
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425. GTcooliebai
Quoting TropicalAnalystwx13:
I just looked at the 12z ECMWF.

My first reaction: Holy freaking crap!

The peak of the hurricane season is among us.
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424. HurricaneDean07
Quoting TropicalAnalystwx13:
I just looked at the 12z ECMWF.

My first reaction: Holy freaking crap!


917 MB?!
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423. Grothar
Quoting barbamz:
Analysis from the site of Mike/Frankfurt (German student of meteorology) about our mediterranean system:

Link

Mike is also on facebook.


I was reading up on this earlier. It doesn't seem to be as bad as they thought, but still very strong.
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422. stormchaser19
Quoting TropicalAnalystwx13:
I just looked at the 12z ECMWF.

My first reaction: Holy freaking crap!


Cat 5
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