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 sar2401:


Ummm...huh?
>



dr m said isaac is gone
Member Since: April 26, 2006 Posts: 5 Comments: 3040
Quoting K8eCane:
its just, what do we do about this?


View Comments (1367)
Leslie a threat to Bermuda; Isaac is gone
Posted by: JeffMasters, 4:30 PM GMT on September 02, 2012


Ummm...huh?
Member Since: October 2, 2004 Posts: 0 Comments: 9743
Miami NWS Disco

LONG TERM...
THE REMNANT LOW OF ISAAC OVER THE SOUTHEAST UNITED STATES WILL
ALSO MOVE SOUTHWARD INTO THE NORTHEAST GULF OF MEXICO LATE THIS
WEEK...BEFORE MOVING SLOWLY EAST ACROSS THE NORTHERN OR CENTRAL
FLORIDA PENINSULA THIS WEEKEND. THIS WILL ALLOW FOR THE STEERING
FLOW TO BECOME SOUTHWEST OVER THE CWA THIS WEEKEND ALONG WITH
BRINGING IN DEEPER TROPICAL MOISTURE TO THE AREA. SO WILL CONTINUE
THE SCATTERED POPS OVER THE CWA WITH THE HIGHEST POPS OVER THE
LAKE OKEECHOBEE AND PALM BEACH COUNTY FOR THIS WEEKEND.

THE LATEST HPC GUIDANCE IS STILL SHOWING RAINFALL TOTALS OF HALF
AN INCH TO ONE INCH OVER MOST OF THE CWA FOR LATE THIS WEEK INTO
THIS WEEKEND WITH EVEN ONE TO TWO INCHES OVER PALM BEACH COUNTY.
HOWEVER...THE CONFIDENCE IS LOW AT THIS TIME FOR THE TOTAL
RAINFALL AMOUNTS DUE TO THE STRENGTH AND LOCATION OF THE LOW.
Member Since: September 10, 2007 Posts: 0 Comments: 10577
Quoting GTcooliebai:
I didn't say it was going to be catastrophic. Also E46Pilot has a roof leak, so he sure doesn't need anymore rain.


I know. I wasn't saying you did.
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Quoting GTcooliebai:
You have roof leak?


Yes, we have a bunch of roof leaks actually, and one really bad one now after Isaac. They were supposed to come to replace the roof last week. Well of course they didn't want to be ripping the roof up while Isaac was at our back door so they delayed it.
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Quoting GPTGUY:


It's funny none of the local mets in New Orleans or the one at the station here along the MS Gulf Coast is calling it the remnants of Isaac or what used to be Isaac..they're calling it a convective complex producing showers and t-storms..I guess they don't want to cause panic saying the I word


Well, they're technically right, it is a mesoscale convective complex. The remnants of Isaac seem to be what gave it a kick start, but it really is its own system now. So far, what happens if the MCC really develops into a low and, if it get back into the Gulf, is pretty speculative. They are not doing a show for weather nerds like us, they just want to tell the public why it's raining or if there's a chance of rain. If this blob turns into something, they'll get into it when and if the NHC says something about it. I can't say I really blame them for not wanting to mention Isaac when it's only peripherally conected to a remnant system.
Member Since: October 2, 2004 Posts: 0 Comments: 9743
Quoting KoritheMan:


There is an enormous difference between localized flooding and flooding on the scale that Isaac produced. Daytime thunderstorms are not going to be catastrophic. Not to say that they can't locally worsen a situation, but it's not really that bad...
I didn't say it was going to be catastrophic. Also E46Pilot has a roof leak, so he sure doesn't need anymore rain.
Member Since: Posts: Comments:
its just, what do we do about this?


View Comments (1367)
Leslie a threat to Bermuda; Isaac is gone
Posted by: JeffMasters, 4:30 PM GMT on September 02, 2012
Member Since: April 26, 2006 Posts: 5 Comments: 3040
Quoting E46Pilot:


So are you showing that it is, or it is not?


It is...lol. It moved from around Kentucky to its current location. A piece split off and moved into the northeast states, but the strongest portion moved south.
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Quoting E46Pilot:


Yup, and that will be me. Although right now might not be to good with all the lightning and all.
You have roof leak?
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Quoting GTcooliebai:
162 hrs. Leslie kills Michael:

so far 300 hrs storm going to s.texas, florida and up the east coaqst all within the past 36 hrs from g.f.s. probably change dozen times more.
Member Since: July 20, 2008 Posts: 0 Comments: 326
Quoting RTSplayer:


Katrina at landfall ranks higher than Andrew on both the HSI and the Integrated Kinetic Energy indexes....FAR higher on IKE index...


Integrated Kinetic Energy is a scientific unit, and is not subject to arbitrary biases.


Katrina over open water dwarfs Andrew's IKE value, and beats Andrew's maximum HSI value by at least 17 points.

Katrina's landfall HSI beats Andrews maximum value by at least 3 points and possibly 6 points.

Katrina's maximum storm surge and wave heights are nearly double that of Andrew, and affected several times the area.


Katrina's Integrated Kinetic Energy is almost exactly double that of Camille, and nearly four times that of Andrew's Florida landfall.


That's right, Katrina had nearly FOUR times the Integrated Kinetic Energy of Andrew's Florida landfall.

Which pretty well means Andrew isn't even in Katrina's league, ya kinda gotta be within at least 20% or so to be considered in the same league/category, IMO.

Source, from NOAA paper:

Tropical Cyclone Destructive Potential by Integrated Kinetic Energy


Turns out, Katrina's LA landfall and Wilma's Florida landfall are rated about the same, then again, Florida isn't below sea level and that approach angle did not maximize storm surge, so there were few deaths from Wilma in Florida, in spite of the botched intensity forecast.



The fact that Andrew ranks so much below Katrina is a reason not to go to a pure "kinetic energy" oriented model. A "danger" scale should capture both the large-storm-size aspects of Katrina and the devastating wind aspects of Andrew.

Andrew had a very concentrated area of devastation. If andrew had the same winds speeds with a diameter for the maximum winds similar to Isaac's, then those max winds would have been extremely close to Miami and it would have killed 10s of thousands of people... so a hypothetical storm with Andrew type winds with a storm the size of Katrina might be a good reason to have a "category 6" on the scale!

Member Since: December 28, 2010 Posts: 0 Comments: 134
Quoting MississippiWx:
Not sure why there is any debate whether the disturbance over Southern AL/FL Panhandle is part of Isaac.

850mb Vort 24 hours ago:



Current:



So are you showing that it is, or it is not?
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Not sure why there is any debate whether the disturbance over Southern AL/FL Panhandle is part of Isaac.

850mb Vort 24 hours ago:



Current:

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Quoting K8eCane:


im sorry. somebody is going to have to get back on the roof.


Yup, and that will be me. Although right now might not be to good with all the lightning and all.
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Getting rain from Isaac.....
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Quoting E46Pilot:
The freaking blue tarp just blew off the roof. Sigh.......


im sorry. somebody is going to have to get back on the roof.
Member Since: April 26, 2006 Posts: 5 Comments: 3040
Quoting GTcooliebai:
It is not good because Isaac caused a lot of flooding in parts of South FL. and this will only add to it. Plus there was a severe warned cell.



There is an enormous difference between localized flooding and flooding on the scale that Isaac produced. Daytime thunderstorms are not going to be catastrophic. Not to say that they can't locally worsen a situation, but it's not really that bad...
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Quoting wxchaser97:

It really looks just like a normal T-storm, how is it not going to be good?
It is not good because Isaac caused a lot of flooding in parts of South FL. and this will only add to it. Plus there was a severe warned cell.

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Will I get some rain from Isaac? Will it develop into a tropical cyclone off my coast, and prompt a renewed influx of customers to Walmart? Will it tease us like Debby? Will it do nothing at all? Questions, questions.
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Quoting wxchaser97:

It really looks just like a normal T-storm, how is it not going to be good?


Well it has a 30mph gust that just blew off the tarp. argghghg, I spent 2 hours putting it on today too.
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The freaking blue tarp just blew off the roof. Sigh.......
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BULLETIN - EAS ACTIVATION REQUESTED
FLASH FLOOD WARNING
NATIONAL WEATHER SERVICE HUNTSVILLE AL
607 PM CDT SUN SEP 2 2012

THE NATIONAL WEATHER SERVICE IN HUNTSVILLE HAS ISSUED A

* FLASH FLOOD WARNING FOR...
FRANKLIN COUNTY IN NORTHWEST ALABAMA...
SOUTHWESTERN LAWRENCE COUNTY IN NORTHWEST ALABAMA...

* UNTIL 900 PM CDT

* AT 605 PM CDT...DOPPLER RADAR INDICATED THUNDERSTORMS PRODUCING
HEAVY RAIN ACROSS ACROSS SOUTHERN PORTIONS OF FRANKLIN AND
LAWRENCE COUNTIES. UP TO THREE INCHES OF RAIN HAVE ALREADY FALLEN.
FLASH FLOODING IS EXPECTED TO BEGIN SHORTLY.

* SOME LOCATIONS THAT WILL EXPERIENCE FLOODING INCLUDE...
RED BAY...PHIL CAMPBELL...VINA AND HODGES.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

EXCESSIVE RUNOFF FROM HEAVY RAINFALL WILL CAUSE FLOODING OF SMALL
CREEKS AND STREAMS...COUNTRY ROADS...AS WELL AS FARMLAND AS WELL
AS OTHER DRAINAGE AREAS AND LOW LYING SPOTS.
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Quoting SFLWeatherman:
Not going to be Good!!!!

It really looks just like a normal T-storm, how is it not going to be good?
Member Since: March 16, 2012 Posts: 123 Comments: 7886
Quoting flcanes:

wow


It was a good idea to remove the inaccurate information, which assigned a fixed range to storm surge for all cat 1 storms. Obviously, doing this assumes that two measures are correlated when they clearly are not.
Member Since: December 28, 2010 Posts: 0 Comments: 134
Quoting Grothar:
local met says the models havent got a grip on isaac's remains just yet..we'll see by thursday maybe
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Not a double post, just a later one.


Member Since: July 17, 2009 Posts: 63 Comments: 23703
336 hrs. a Donna like track

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Quoting MAweatherboy1:
300 hours... Chances are the rest of the run will show this bombing out in the Gulf:


Nope... Takes a right turn into FL.

Member Since: February 11, 2012 Posts: 79 Comments: 7291
Member Since: July 17, 2009 Posts: 63 Comments: 23703
486
WFUS51 KPHI 042230
TORPHI
NJC005-007-042300-
/O.NEW.KPHI.TO.W.0005.120904T2230Z-120904T2300Z/

BULLETIN - EAS ACTIVATION REQUESTED
TORNADO WARNING
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
630 PM EDT TUE SEP 4 2012

THE NATIONAL WEATHER SERVICE IN MOUNT HOLLY NJ HAS ISSUED A

* TORNADO WARNING FOR...
WEST CENTRAL BURLINGTON COUNTY IN SOUTHERN NEW JERSEY...
NORTHWESTERN CAMDEN COUNTY IN SOUTHERN NEW JERSEY...
THIS INCLUDES THE CITY OF GLOUCESTER CITY...

* UNTIL 700 PM EDT

* AT 629 PM EDT...NATIONAL WEATHER SERVICE DOPPLER RADAR INDICATED A
SEVERE THUNDERSTORM CAPABLE OF PRODUCING A TORNADO NEAR BELLMAWR...
OR NEAR GLOUCESTER CITY...MOVING NORTHEAST AT 15 MPH.

* THE TORNADO WILL BE NEAR...
MAGNOLIA BY 640 PM EDT...
CHERRY HILL...SPRINGDALE AND VOORHEES BY 655 PM EDT...
GREENTREE...MARLTON...MOUNT LAUREL AND EVESHAM BY 700 PM EDT...

PRECAUTIONARY/PREPAREDNESS ACTIONS...

THE SAFEST PLACE TO BE DURING A TORNADO IS IN A BASEMENT. GET UNDER A
WORKBENCH OR OTHER PIECE OF STURDY FURNITURE. IF NO BASEMENT IS
AVAILABLE...SEEK SHELTER ON THE LOWEST FLOOR OF THE BUILDING IN AN
INTERIOR HALLWAY OR ROOM SUCH AS A CLOSET. USE BLANKETS OR PILLOWS TO
COVER YOUR BODY AND ALWAYS STAY AWAY FROM WINDOWS.

IF IN MOBILE HOMES OR VEHICLES...EVACUATE THEM AND GET INSIDE A
SUBSTANTIAL SHELTER. IF NO SHELTER IS AVAILABLE...LIE FLAT IN THE
NEAREST DITCH OR OTHER LOW SPOT AND COVER YOUR HEAD WITH YOUR HANDS.

PLEASE REPORT HAIL OR STRONG WINDS TO THE NATIONAL WEATHER SERVICE BY
CALLING TOLL FREE...1-877-633-6772...WHEN YOU CAN DO SO SAFELY.



LAT...LON 3985 7482 3983 7508 3986 7511 3991 7514
3992 7513 4003 7493
TIME...MOT...LOC 2231Z 247DEG 12KT 3987 7508



HEAVENER
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300 hours... Chances are the rest of the run will show this bombing out in the Gulf:

Member Since: February 11, 2012 Posts: 79 Comments: 7291
264 hours:

Member Since: February 11, 2012 Posts: 79 Comments: 7291
Quoting bappit:

Looking at that graph you posted, it seems the record was beaten back in August.

Yeah, you're right, I guess we've already done it and are just going further in the hole now.

GFS 228 hours:

Member Since: February 11, 2012 Posts: 79 Comments: 7291
Quoting GTcooliebai:
162 hrs. Leslie kills Michael:



A big "ouch" for Nfld.
Member Since: August 29, 2009 Posts: 12 Comments: 482
Quoting MAweatherboy1:
We're all but assured to beat 2007's record this year, and probably by a pretty good margin:


Looking at that graph you posted, it seems the record was beaten back in August.
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168 hrs. landfall on St. John's Newfoundland and Labrador:

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Quoting indianrivguy:


which is dropping more water on an area trying to recover from 14 inches of rain from Isaac...

the areas hardest hit, Wellington (West of 441)/Loxahatchee/Loxahatchee Groves/The Acreage, received in excess of 22" in many areas. I am in Boynton Beach, just East of 441 and we received in excess of 14".
Member Since: August 15, 2008 Posts: 0 Comments: 2515
20inches
Quoting indianrivguy:


which is dropping more water on an area trying to recover from 14 inches of rain from Isaac...
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Quoting Chucktown:


GFS and most of the models don't do well with upwelling. If Leslie is moving slower than 10 kts, it will not be 938 mb by Friday afternoon.

"ADDITIONALLY...THE UNIVERSITY OF MIAMI-RSMAS OCEAN
ANALYSIS INDICATES THAT THE HEAT CONTENT OF THE OCEAN BELOW LESLIE
IS HIGH...WHICH MAY LIMIT THE IMPACTS OF COLD WATER UPWELLING FROM
THE SLOW-MOVING CYCLONE."

The GFS says 978 millibars, not 938 millibars, by the way.
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Quoting hunkerdown:

Don't think so as they would be going in somewhat opposite directions.
Looks more like Leslie absorbs Michael.
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Member Since: July 17, 2009 Posts: 63 Comments: 23703
Quoting GTcooliebai:
132 hrs. a fujiwhara interaction?


Don't think so as they would be going in somewhat opposite directions.
Member Since: August 15, 2008 Posts: 0 Comments: 2515
Quoting Bluestorm5:


It's just a typical storm...


which is dropping more water on an area trying to recover from 14 inches of rain from Isaac...
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Quoting MississippiWx:
Here comes Isaac again.



It's funny none of the local mets in New Orleans or the one at the station here along the MS Gulf Coast is calling it the remnants of Isaac or what used to be Isaac..they're calling it a convective complex producing showers and t-storms..I guess they don't want to cause panic saying the I word
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at about 64 W, only 5 degrees east of of Cape Cod.
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162 hrs. Leslie kills Michael:

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Wave moving towards the Antilles.

Member Since: July 17, 2009 Posts: 63 Comments: 23703
Quoting SFLWeatherman:
Not going to be Good!!!!


It's just a typical storm...
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Quoting SFLWeatherman:
Not going to be Good!!!!


Desperate times for S FL svr weather fans.
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About JeffMasters

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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