Leslie near hurricane strength; Son of Isaac (90L) emerges in the Gulf

By: Dr. Jeff Masters , 3:05 PM GMT on September 05, 2012

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Tropical Storm Leslie is growing more organized and is approaching hurricane strength on its slow voyage northwards at 2 mph towards the island of Bermuda. Moderately high wind shear of 15 - 20 knots due to strong upper-level winds out of the northwest continues to keep most of Leslie's heavy thunderstorms pushed to the east side of the storm, but satellite loops show that Leslie now has an impressive blow-up of heavy thunderstorms with cold cloud tops near its center. Leslie's slow forward speed means that the storm is staying over the cold water stirred up by the storm's winds, inhibiting intensification, but the waters underneath Leslie are warm to great depth, making this less of a factor than usual. According to the latest SHIPS model forecast, the shear is expected to fall steadily today, reaching the low category, 5 - 10 knots, by Thursday afternoon. Leslie is over warm ocean waters of 29 - 30°C, and the reduction in shear and warm waters should aid intensification, and potentially allow Leslie to be at Category 2 strength at its closest pass by Bermuda Saturday night and early Sunday morning, as indicated by the official NHC forecast. The latest 11 am EDT NHC wind probability forecast calls for a 48% chance that Leslie will be a Category 2 or stronger hurricane Sunday morning at 8 am EDT. 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 42-hour period of tropical storm-force winds beginning Saturday morning near 2 am AST, and lasting until 8 pm AST Sunday night. The official NHC forecast shows Leslie nearly making a direct hit on Bermuda, and Leslie will be 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. NHC is predicting that hurricane-force winds will extend outwards from the center of Leslie by 35 miles on Thursday night, and I expect this will increase to at least 60 miles by early Sunday morning, when Leslie will be making its closest pass by Bermuda.


Figure 1. Morning satellite image of Tropical Storm Leslie. Heavy thunderstorms have built near the center of the storm, and Leslie is near hurricane strength.

Leslie's impact on Canada
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. The timing of this trough is such that Leslie will be pulled northwards and then north-northeastwards over the weekend. There are still significant differences among the models in the timing and speed of Leslie's track over the weekend, but we can now dismiss the threat of Leslie making a direct hit on New England. The storm is likely to make landfall in Nova Scotia or Newfoundland, though there are significant differences in the models' predictions of the timing of Leslie's arrival in Canada. The GFS model predicts an early Tuesday landfall in Newfoundland, but the ECMWF model is much faster and farther west, predicting a Monday afternoon landfall in Nova Scotia. Large swells from Leslie are pounding the entire Eastern Seaboard, and these waves will increase in size as Leslie grows in strength this week. The Hurricane Hunters are scheduled to make their first flight into Leslie on Thursday afternoon.


Figure 2. Morning radar image of Invest 90L off the coast of the Florida Panhandle.

Son of Isaac: Invest 90L emerges in the Gulf of Mexico
During Tropical Depression Isaac's trek across the center of the U.S. during the Labor Day weekend, the storm was ripped in half. One portion of the storm moved over the Northeast U.S., bringing heavy rains there, and another portion sank southwards over Alabama. You can see this split by studying an animation of the vorticity at 850 mb (the amount of spin at low levels of the atmosphere, near 5,000 feet above sea level) from the University of Wisconsin. This remnant of Isaac, which still maintained some of Isaac's spin, brought heavy rains of 5 - 10 inches that caused flooding problems over portions of Alabama on Tuesday. The storm has now emerged over the Gulf of Mexico near the Florida Panhandle, and was designated Invest 90L this morning by NHC. In their 8 am Tropical Weather Outlook, NHC gave 90L a 20% chance of developing into a tropical depression by Friday morning. According to NHC naming rules, "if the remnant of a tropical cyclone redevelops into a tropical cyclone, it is assigned its original number or name". Since "the remnant" refers to the primary remnant, and 90L does not fit the definition of a "primary remnant", the storm will be given a new name should it develop into a tropical storm, according to information posted on the NHC Facebook page. Esau or Jacob--the names of the sons of the biblical Isaac--would be fitting names for 90L, but the next storm on the list of Atlantic storms is Nadine.

Long-range radar out of Mobile, Alabama shows a large area of heavy rainfall along the coast due to 90L. The echoes do show some spiral banding behavior, but there is only a slight evidence of rotation to the storm. Infrared satellite loops show that the thunderstorms associated with 90L are not that vigorous and do not have particularly cold cloud tops, and the area covered by the thunderstorms is relatively small. Wind shear is a high 20 - 30 knots over the northern Gulf of Mexico, but is predicted to fall to the moderate range, 10 - 20 knots, by Thursday afternoon. Ocean temperatures in the Gulf have been cooled down considerably by the passage of Hurricane Isaac last week, and are 28 - 28.5°C. This is still plenty warm enough to support formation of a tropical storm, and I expect 90L will increase in organization on Thursday and Friday as it moves slowly south or south-southwest. 90L could become a tropical depression as early as Thursday, though Friday is more likely. A hurricane hunter aircraft is scheduled to investigate 90L on Thursday afternoon. A trough of low pressure and an associated surface cold front will move southeastwards over the northern Gulf of Mexico on Sunday, and this trough should be capable of pulling 90L to the northeast to a landfall along the Florida Panhandle or west coast of Florida on Sunday.


Figure 3. Morning satellite image of Tropical Storm Michael.

Tropical Storm Michael in the Central Atlantic
Tropical Storm Michael has strengthened to 50 mph winds, and appears to have a favorable enough environment to become a hurricane later this week. Satellite loops show that this is a small tropical cyclone, far out over the open Atlantic, and none of the models show that Michael will threaten any land areas.

Elsewhere in the Atlantic
The GFS and ECMWF models are predicting that a new tropical wave due to move off the coast of Africa on Friday will develop into a tropical depression by the middle of next week. It's too early to tell if this system might threaten the Lesser Antilles Islands.

Jeff Masters

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1374. Slamguitar
4:14 PM GMT on September 06, 2012
Michael tied with Gordon in pressure. 965mb.
Member Since: July 2, 2011 Posts: 0 Comments: 1183
1373. InPCola
3:46 PM GMT on September 06, 2012
Quoting MNhockeymama:


We can't do a lot to help here in MN, so it feels like I'm sending help to the people affected; hubs calls and says, "Well, we just LIT UP A TOWN!" He also likes to help and really enjoys getting electricity back up for people who lose it during storms.

Thank goodness there are people who enjoy doing it, I can't imagine where we'd be after a storm if all the power company workers were just in it for the money and took no personal satisfaction in the work. Tell him that we do appreciate it, and most people who haven't been through a big storm can't imagine how much we do. It's just so much easier to deal with everything else when you can have lights and AC vs. a hot and humid house for days to weeks after, oppressively dark both from the lack of power and from shutters if you put them up.

It's amazing how just having light that isn't coming from a candle or flashlight can cheer you after a storm. Even if it's also showing you the extent of the damage you've taken more clearly... :p
Member Since: August 16, 2007 Posts: 0 Comments: 10
1372. Clearwater1
3:34 PM GMT on September 06, 2012
Quoting Grothar:
Looks like a new low wants to form closer to the convection. This would move the center quite a bit South before it starts its trek towards Florida.

Yes. One can see the naked swirl north of the blob. The big blob may have hard time wrapping around the low, but you never know. In any event, the cold front is forecast to catch it and pull it towards central or north FL.. A lot of rain headed that way. If nothing forms in a day or so, the shear will guarantee nothing other than a rainmaker. Which by the way is fine with me. In fact, could even do without the rain as well.
Member Since: August 26, 2006 Posts: 0 Comments: 1548
1371. KEEPEROFTHEGATE (Mod)
3:28 PM GMT on September 06, 2012
Quoting jeffs713:

Let me guess, you want it to go right over your house, too?

I would be perfectly fine to not have a cat 5 for another 5 years. I'm also sure that 99.999999999% of the western Atlantic coast would be happy with it, too.


best chance for a five would be latter half of the the peak
2nd week of october on
side winder moving ne ward
from the sw carb nw carb
cen boc in gom
Member Since: July 15, 2006 Posts: 174 Comments: 54353
1370. VINNY04
3:28 PM GMT on September 06, 2012
Quoting VR46L:


Umm No thanks ...
i second that! maybe a cat 1 or 2. but not more than that.
Member Since: March 6, 2011 Posts: 0 Comments: 243
1369. VR46L
3:26 PM GMT on September 06, 2012
Quoting wunderkidcayman:
hey guys we need a cat 5 out in the atlantic because we haven't had one since 07 that 5 year now


Umm No thanks ...
Member Since: March 1, 2012 Posts: 0 Comments: 6927
1368. MNhockeymama
3:26 PM GMT on September 06, 2012
Quoting MahFL:
I was wondering about how that person made $ from canes, not people in general lol. After Katrina the co I work for sold 1000's of generators and refridgerators.


One thing you regular bloggers should be proud of is the amount of education you give those of us who follow the hurricanes - I learn more here every year than I do anywhere else.

Re: making money following hurricanes, it is a hard thing to explain to people that one gets a little excited when the hurricanes start looking like they'll make landfall in the US - do not wish harm to anyone, but do look forward to weeks/months of really good work for my husband when he goes to help with the power restoration. We can't do a lot to help here in MN, so it feels like I'm sending help to the people affected; hubs calls and says, "Well, we just LIT UP A TOWN!" He also likes to help and really enjoys getting electricity back up for people who lose it during storms.
Member Since: September 4, 2010 Posts: 0 Comments: 124
1367. GetReal
3:26 PM GMT on September 06, 2012



Link


I am not predicting 90L to do so, but it does appear to be still sinking south. If by some chance 90L does happen to get south of 24N, and is no more than a TD, it may not get whisked off towards the east with that trough.
Member Since: July 4, 2005 Posts: 204 Comments: 8896
1366. LargoFl
3:26 PM GMT on September 06, 2012
Member Since: August 6, 2011 Posts: 4 Comments: 39147
1365. VINNY04
3:26 PM GMT on September 06, 2012
Quoting sar2401:


That's one consideration, I'm sure, but the range, sensor capabilities, and higher ceiling are really selling points. The Global Hawk can put a Hellfire missile right down the chimney of a house anywhere from 500 to 50,000 feet, so looking into a hurricane should be relatively easy with the sensor package on those babies. :)
yah true. i didnt think about that. I love those drones!
Member Since: March 6, 2011 Posts: 0 Comments: 243
1364. sar2401
3:25 PM GMT on September 06, 2012
Quoting VINNY04:
it is because it will take out the possibility of people dying if a plane goes down.


That's one consideration, I'm sure, but the range, sensor capabilities, and higher ceiling are really selling points. The Global Hawk can put a Hellfire missile right down the chimney of a house anywhere from 500 to 50,000 feet, so looking into a hurricane should be relatively easy with the sensor package on those babies. :)
Member Since: October 2, 2004 Posts: 0 Comments: 16047
1363. Skyepony (Mod)
3:25 PM GMT on September 06, 2012
Quoting roberie:


Yea that looks like it. Here is a link to the study they are doing with these long range planes.


Good link, thanks. I knew it was some high altitude microwave & such but that might help find some of the data.

Quoting jeffs713:

Note the altitude they are flying it at... 55k-65k. Isn't the G-IV's ceiling at 45k?


This is almost like a controlled satellite, but low enough your dropsondes don't burn up.
Member Since: August 10, 2005 Posts: 174 Comments: 38155
1362. WunderAlertBot (Admin)
3:24 PM GMT on September 06, 2012
JeffMasters has created a new entry.
1361. LargoFl
3:24 PM GMT on September 06, 2012
Quoting GTcooliebai:
say GT..local met said my area got an inch of rain this morning, man it sure poured rain by me for awhile there..how about your area?
Member Since: August 6, 2011 Posts: 4 Comments: 39147
1360. Grothar
3:21 PM GMT on September 06, 2012
Quoting washingtonian115:
The one percent is JFV.


That would be .000000001% :)
Member Since: July 17, 2009 Posts: 71 Comments: 26477
1359. VINNY04
3:18 PM GMT on September 06, 2012
Quoting sar2401:


Yep, the service ceiling is 45k, but it will do 50k if it has to. I've been wondering when the were going to fly the UAV. I think this really the future for HH aircraft.
it is because it will take out the possibility of people dying if a plane goes down.
Member Since: March 6, 2011 Posts: 0 Comments: 243
1358. washingtonian115
3:18 PM GMT on September 06, 2012
Quoting jeffs713:

Let me guess, you want it to go right over your house, too?

I would be perfectly fine to not have a cat 5 for another 5 years. I'm also sure that 99.999999999% of the western Atlantic coast would be happy with it, too.
The one percent is JFV.
Member Since: August 14, 2010 Posts: 10 Comments: 17081
1357. 7544
3:17 PM GMT on September 06, 2012
90l now moving southward
Member Since: May 6, 2007 Posts: 0 Comments: 6855
1356. washingtonian115
3:17 PM GMT on September 06, 2012
Quoting mcluvincane:


Cyber I'm a female for one and definitely not a troll, i follow hurricanes for a living and been through more than you could imagine. You sir are out of line
Your a female o_0?.
Member Since: August 14, 2010 Posts: 10 Comments: 17081
1355. wpb
3:17 PM GMT on September 06, 2012
http://www.cpc.ncep.noaa.gov/products/analysis_moni toring/enso_advisory/index.shtml
Member Since: May 28, 2011 Posts: 0 Comments: 573
1354. sar2401
3:16 PM GMT on September 06, 2012
Quoting jeffs713:

Note the altitude they are flying it at... 55k-65k. Isn't the G-IV's ceiling at 45k?


Yep, the service ceiling is 45k, but it will do 50k if it has to. I've been wondering when the were going to fly the UAV. I think this really the future for HH aircraft.
Member Since: October 2, 2004 Posts: 0 Comments: 16047
1353. DrMickey
3:16 PM GMT on September 06, 2012
Quoting NEwxguy:



lurking

Didn't recognize you without the Flying Elvis!
Member Since: May 22, 2005 Posts: 0 Comments: 162
1352. jeffs713
3:16 PM GMT on September 06, 2012
Quoting wunderkidcayman:
hey guys we need a cat 5 out in the atlantic because we haven't had one since 07 that 5 year now

Let me guess, you want it to go right over your house, too?

I would be perfectly fine to not have a cat 5 for another 5 years. I'm also sure that 99.999999999% of the western Atlantic coast would be happy with it, too.
Member Since: August 3, 2008 Posts: 16 Comments: 5885
1351. VINNY04
3:15 PM GMT on September 06, 2012
Quoting Skyepony:


I think this is it. Ryan RQ-4A Global Hawk flies as NASA 872. Its Air Force serial number is 00-2006. It was the sixth Global Hawk built by Ryan. Tropical Atlantic should link it with a pic once it's in the air.

thats a nice craft! i think its ingenious to fly a UAV into storms.
Member Since: March 6, 2011 Posts: 0 Comments: 243
1350. sar2401
3:13 PM GMT on September 06, 2012
Quoting wunderkidcayman:
hey guys we need a cat 5 out in the atlantic because we haven't had one since 07 that 5 year now


No, we dont need one....you just want one. :)
Member Since: October 2, 2004 Posts: 0 Comments: 16047
1349. jeffs713
3:13 PM GMT on September 06, 2012
Quoting Skyepony:


I think this is it. Ryan RQ-4A Global Hawk flies as NASA 872. Its Air Force serial number is 00-2006. It was the sixth Global Hawk built by Ryan. Tropical Atlantic should link it with a pic once it's in the air.


Note the altitude they are flying it at... 55k-65k. Isn't the G-IV's ceiling at 45k?
Member Since: August 3, 2008 Posts: 16 Comments: 5885
1347. gordydunnot
3:11 PM GMT on September 06, 2012
Mikey likes it out there in the middle of nowhere. I do think we teased him a little to much about his size. So I dare not say to much about his location, he is an excitable young lad.
Member Since: August 18, 2008 Posts: 0 Comments: 3113
1346. roberie
3:10 PM GMT on September 06, 2012
Quoting Skyepony:


I think this is it. Ryan RQ-4A Global Hawk flies as NASA 872. Its Air Force serial number is 00-2006. It was the sixth Global Hawk built by Ryan. Tropical Atlantic should link it with a pic once it's in the air.



Yea that looks like it. Here is a link to the study they are doing with these long range planes.
Member Since: December 17, 2003 Posts: 0 Comments: 36
1345. Skyepony (Mod)
3:09 PM GMT on September 06, 2012
That's yesterday's plan of the day though. They are running late with today's...
Member Since: August 10, 2005 Posts: 174 Comments: 38155
1344. VR46L
3:09 PM GMT on September 06, 2012
Quoting TomballTXPride:

actually looks prettier in that image as rainbow really shows her imperfections. But yeah still lots of work to do to look decent and hope it stays crappy for bermuda's sake.


She looks like a bit like Isaac crossing around the keys ... a mess
Member Since: March 1, 2012 Posts: 0 Comments: 6927
1342. Skyepony (Mod)
3:07 PM GMT on September 06, 2012
Quoting wunderkidcayman:

yeah I know bit I am talking about that one going in Leslie which craft is that I don't remember hearing about it


I think this is it. Ryan RQ-4A Global Hawk flies as NASA 872. Its Air Force serial number is 00-2006. It was the sixth Global Hawk built by Ryan. Tropical Atlantic should link it with a pic once it's in the air.

Member Since: August 10, 2005 Posts: 174 Comments: 38155
1341. MahFL
3:05 PM GMT on September 06, 2012
WXMOD will go nuts when he finds out a UAV is flying into Leslie, lol.
Member Since: June 9, 2004 Posts: 0 Comments: 3543
1340. wunderkidcayman
3:04 PM GMT on September 06, 2012
hey guys we need a cat 5 out in the atlantic because we haven't had one since 07 that 5 year now
Member Since: June 13, 2009 Posts: 2 Comments: 12150
1339. MahFL
3:03 PM GMT on September 06, 2012
I was wondering about how that person made $ from canes, not people in general lol. After Katrina the co I work for sold 1000's of generators and refridgerators.
Member Since: June 9, 2004 Posts: 0 Comments: 3543
1338. uptxcoast
3:03 PM GMT on September 06, 2012
Quoting MahFL:

How do you make $ following hurricanes ?




Guy who follows storms and took the tree off my Dad's house after Ike.

Well, the image is not displaying but is in my photo album on WU. The guy has arm of tattoos with each storm he has chased and made money from.
Member Since: September 23, 2005 Posts: 6 Comments: 235
1336. islander101010
3:01 PM GMT on September 06, 2012
oh.dont.forget.brothers.of.policians....they.do.goo d.too
Member Since: September 11, 2010 Posts: 1 Comments: 4724
1334. wunderkidcayman
3:01 PM GMT on September 06, 2012
Quoting sar2401:


Looks like they are going to fly on 90L.

yeah I know bit I am talking about that one going in Leslie which craft is that I don't remember hearing about it
Member Since: June 13, 2009 Posts: 2 Comments: 12150
1333. GTcooliebai
3:00 PM GMT on September 06, 2012
Member Since: August 31, 2009 Posts: 0 Comments: 5628
1332. MahFL
2:58 PM GMT on September 06, 2012
Quoting mcluvincane:


Cyber I'm a female for one and definitely not a troll, i follow hurricanes for a living and been through more than you could imagine. You sir are out of line


Ah you mean you've been through the aftermath of hurricanes.
Member Since: June 9, 2004 Posts: 0 Comments: 3543
1331. VR46L
2:58 PM GMT on September 06, 2012
Quoting TomballTXPride:
this looks worse than Abrams in that purple potato sack dress that one day.



sure is a fugly mess!!

Member Since: March 1, 2012 Posts: 0 Comments: 6927
1330. sar2401
2:58 PM GMT on September 06, 2012
Quoting wunderkidcayman:

huh? which one is that?


Looks like they are going to fly on 90L.
Member Since: October 2, 2004 Posts: 0 Comments: 16047
1329. NOLALawyer
2:57 PM GMT on September 06, 2012
Quoting MahFL:

How do you make $ following hurricanes ?


Hurricanes are big business. This place has members that are adjusters, contractors, attorneys and even FEMA employees.
Member Since: September 3, 2009 Posts: 0 Comments: 520
1328. StormHype
2:57 PM GMT on September 06, 2012
Quoting JasonRE:
Is there any chance that Louisiana sees any of 90L? Lafayette here.


Where were you? It already did yesterday morning. ;-)
Member Since: May 31, 2007 Posts: 0 Comments: 1204
1327. sar2401
2:57 PM GMT on September 06, 2012
Quoting StormJunkie:
The forgotten community of Pearlington, MS...





So true. If wasn't in Louisiana, you'd think, by just following the media, that nothing ever happened. MS is always just a "landmass". I'm glad to see the houses are still standing. I'll never forget Bay St. Louis after Katrina. :(
Member Since: October 2, 2004 Posts: 0 Comments: 16047
1326. wunderkidcayman
2:56 PM GMT on September 06, 2012
Quoting GTcooliebai:
000
NOUS42 KNHC 051436
REPRPD
WEATHER RECONNAISSANCE FLIGHTS
CARCAH, NATIONAL HURRICANE CENTER, MIAMI, FL.
1035 AM EDT WED 05 SEPTEMBER 2012
SUBJECT: TROPICAL CYCLONE PLAN OF THE DAY (TCPOD)
VALID 06/1100Z TO 07/1100Z SEPTEMBER 2012
TCPOD NUMBER.....12-109


I. ATLANTIC REQUIREMENTS
1. TROPICAL STORM LESLIE
FLIGHT ONE --NASA872--
A. 07/0130Z
B. NASA872 0112A LESLIE SURVEILLANCE AV-6
C. 06/1900Z
D. 26.9N 63.3W
E. 07/0130Z TO 07/1130Z
F. 55,000 TO 65,000 FT
G. IP 30.1N 81.2W OUTFLOW LAYER AXIS CYCLONIC S TO N

2. SUSPECT AREA (GULF OF MEXICO)
FLIGHT ONE --TEAL 71--
A. 06/1800Z D. 28.5N 87.8W
B. AFXXX 01DDA INVEST E. 06/1730Z TO 06/2130Z
C. 06/1700Z F. SFC TO 10,000 FT

3. SUCCEEDING DAY OUTLOOK:
A. BEGIN 12-HRLY FIXES AT 07/1200Z IF SUSPECT AREA DEVELOPS.
B. FIX OF TROPICAL STORM LESLIE AT 07/1800Z NEAR 26.6N 63.2W.

huh? which one is that?
Member Since: June 13, 2009 Posts: 2 Comments: 12150
1325. JasonRE
2:55 PM GMT on September 06, 2012
Is there any chance that Louisiana sees any of 90L? Lafayette here.
Member Since: August 6, 2012 Posts: 0 Comments: 122
1324. RTSplayer
2:53 PM GMT on September 06, 2012
Based on this, I'd rate Leslie unofficially as an "10" on the HSI.



I'd rate Michael an 19 on HSI.



I ranked Isaac as a 20 at landfall.


Member Since: January 25, 2012 Posts: 33 Comments: 1520

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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.