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

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

Share this Blog
53
+

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

Reader Comments

Comments will take a few seconds to appear.

Post Your Comments

Please sign in to post comments.

or Join

Not only will you be able to leave comments on this blog, but you'll also have the ability to upload and share your photos in our Wunder Photos section.

Display: 0, 50, 100, 200 Sort: Newest First - Order Posted

Viewing: 674 - 624

Page: 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 | 16 | 17 | 18 | 19 | 20 | 21 | 22 | 23 | 24 | 25 | 26 | 27 | 28Blog Index

Quoting bappit:

Yep, I feel more like I do today than I did yesterday.

:>)
Member Since: Posts: Comments:
Quoting HurrMichaelOrl:


I know Hurricane David hit in 1979, and South Florida was directly affected. Still, nothing compared to Betsy or Andrew.


I seem to recall a couple of pre 1965 storms... Alma, Cleo and Betsy if memory serves. I remember my parents pulling down the sun awning over the jalousie (sp) windows and putting up the shutters on the all brick house. Filing the bath tub with water and getting the candles ready. All fun when your kid.
Member Since: August 30, 2008 Posts: 0 Comments: 173
Quoting KoritheMan:


What do you mean?


Not sure - but you have to wonder!
Member Since: Posts: Comments:
Quoting Charmeck:
This is sure an impressive picture - - I'm still wondering if there is some unknow force affecting all of this??? Link


Huh?
Member Since: Posts: Comments:
90L is up to 50%.
Member Since: March 16, 2012 Posts: 127 Comments: 7927
Ah hell. I'll give it to you Largo. :)
Member Since: March 7, 2007 Posts: 552 Comments: 19871
..................yes 50%
Member Since: August 6, 2011 Posts: 4 Comments: 36847
Quoting TropicalAnalystwx13:
Since it hasn't been posted yet...90L is up to 50%.
.
Member Since: August 14, 2010 Posts: 10 Comments: 16383
Quoting washingtonian115:
Be funny if Karen came back for revenge next year just to get back at the people on the blog.Lol.
I have heard rumblings that 2013 will be a La Nina year, so it is possible.
Member Since: August 1, 2012 Posts: 0 Comments: 436
Quoting stormchaser19:
At least Leslie is going to pass over Greenland
and where is this one going?? hope out to sea
Member Since: Posts: Comments:
Since it hasn't been posted yet...90L is up to 50%.
Member Since: Posts: Comments:
Quoting CybrTeddy:


You'd be correct, it probably will be a hurricane soon.
CI# /Pressure/ Vmax
4.4 / 981.7mb/ 74.6kt


With the satellite appearance and that it will probably be a hurricane.

Quoting allancalderini:
I think is one now.

He is very close if not one.
Member Since: March 16, 2012 Posts: 127 Comments: 7927
Quoting Charmeck:
This is sure an impressive picture - - I'm still wondering if there is some unknow force affecting all of this??? Link



What do you mean?
Member Since: March 7, 2007 Posts: 552 Comments: 19871
Quoting lobdelse81:
Any threats on the horizon besides 90L, Leslie, or Mike that we need to keep an eye on past this weekend?


GFS develops another Cape Verde storm in about four or five days and makes it a hurricane.
Member Since: March 7, 2007 Posts: 552 Comments: 19871
At least Leslie is going to pass over Greenland
Member Since: Posts: Comments:
Quoting Charmeck:
This is sure an impressive picture - - I'm still wondering if there is some unknow force affecting all of this???a href="http://www.ssd.noaa.gov/goes/east/tatl/flash -wv.html" target="_blank" onclick="if(!checkUrl(this.href)) return false;" rel="nofollow"
god!!
Member Since: Posts: Comments:
Quoting washingtonian115:
Be funny if Karen came back for revenge next year just to get back at the people on the blog.Lol.


Karen and I have no issues with each other :)
Member Since: Posts: Comments:
This is sure an impressive picture - - I'm still wondering if there is some unknow force affecting all of this??? Link

Member Since: Posts: Comments:
Leave Karen alone.
Member Since: August 14, 2010 Posts: 10 Comments: 16383
Quoting washingtonian115:
Be funny if Karen came back for revenge next year just to get back at the people on the blog.Lol.
no it wouldnt :( but karma is a beach!! please dont ban me :/ have a sense of humor
Member Since: Posts: Comments:
RECORD BREAKING WET-AUGUST............After a mixed-bag of rainfall for much of the summer, the month of August was characterized by
periods of widespread heavy rainfall. Most of the eastern metro region of South Florida received
anywhere from 10 to 20 inches of rain, with another area of over 10 inches over western sections of
Collier and Hendry counties (Figure 1).
Of the 31 sites that report daily rainfall over mainland South Florida, all but five reported monthly
rainfall in excess of 10 inches. Two locations, Palm Beach Gardens and West Palm Beach, exceeded 20
inches for the month. Tropical Storm Isaac was responsible for much of this rainfall (Figure 2), but
heavy rain fell on several other days in August as South Florida was under a predominantly moist
southerly wind flow resulting from lower atmospheric pressure over the eastern half of the United
States (Figures 3 and 4). According to the South Florida Water Management District, it was the 5
th
wettest August for the district since 1932 (Note: the district includes areas north and northeast of Lake
Okeechobee not covered by NWS Miami).
In areas where summer rainfall was copious even before August, particularly over the east coast
metro, year-to-date rainfall is on pace to break the all-time record for a calendar year. These locations
include Miami International Airport (68.48 inches as of 8/31), Miami Beach (48.34 inches) and The
Redland (63.54 inches). West Palm Beach is on pace for their second-wettest year on record (61.47
inches).
Member Since: August 6, 2011 Posts: 4 Comments: 36847
Quoting zoomiami:
Someone a ways back was asking about Karen -- Karen was a storm formed about 5?? years ago -- that danced across the atlantic with basically a circulation and nothing else!

We watched that silly storm for days on end, and then it started to be part of the lore of missing circulations. Always there, Karen just waits to be found again.


Ah yes, Hurricane Karen of 2007. That was an interesting one to track. Once Karen died, it looked like it would regenerate again and again, and when we weren't looking, it did in the end regenerate into a separate tropical depression. We still believe that system is still out there, waiting to return.

Karen is the 'K' storm on next years naming list, so that will be interesting to relieve that fun.
Member Since: July 8, 2005 Posts: 259 Comments: 23564
Any threats on the horizon besides 90L, Leslie, or Mike that we need to keep an eye on past this weekend?
Member Since: Posts: Comments:
Quoting KoritheMan:


Shear and cooler waters.

ENSO is not the deciding factor for seasonal activity.
your right but it is pretty rare to have elnino like conditions in a lanina year!
Member Since: Posts: Comments:
Be funny if Karen came back for revenge next year just to get back at the people on the blog.Lol.
Member Since: August 14, 2010 Posts: 10 Comments: 16383
Quoting floridabuckeyes:


Hey Gro....I think you may have forgotten one....David 1979...I believe it hit around Palm Beach somewhere....still been pretty darn lucky!!!!


No, I didn't forget. It barely touched the coast at Palm Beach but made another close Landfall near New Smyrna Beach while hugging most of the coast. We were still living in Miami then and even though it came close it barely gave us Tropical Storm force winds.
Member Since: July 17, 2009 Posts: 69 Comments: 25308
Member Since: August 6, 2011 Posts: 4 Comments: 36847
Quoting windshear1993:
i just thought about the 1973 season NOT 1972..1973 why was it so inactive and it was a la nina year??


Shear and cooler waters.

ENSO is not the deciding factor for seasonal activity.
Member Since: March 7, 2007 Posts: 552 Comments: 19871
Quoting wxchaser97:
I think Michael will be a hurricane soon.


You'd be correct, it probably will be a hurricane soon.
CI# /Pressure/ Vmax
4.4 / 981.7mb/ 74.6kt

Member Since: July 8, 2005 Posts: 259 Comments: 23564
Someone a ways back was asking about Karen -- Karen was a storm formed about 5?? years ago -- that danced across the atlantic with basically a circulation and nothing else!

We watched that silly storm for days on end, and then it started to be part of the lore of missing circulations. Always there, Karen just waits to be found again.
Member Since: Posts: Comments:
GEMS model has 90L crossing Florida intensifying in the ATL, then pushed back west to Fl/Ga by the ridge.

Link
Member Since: Posts: Comments:
Quoting 954FtLCane:

Cause the NHC was watching the Dolphins go undefeated and win back to back super bowls in '72 & '73 and obviously not paying attention to the tropics!
lmao didnt know the dolphins was that good back in the day never heard of back to back superbowl champs wow
Member Since: Posts: Comments:
Quoting bappit:

Yep, I feel more like I do today than I did yesterday.
Oh poo I made a mistake :).
Member Since: August 14, 2010 Posts: 10 Comments: 16383
Member Since: August 6, 2011 Posts: 4 Comments: 36847
Quoting lobdelse81:

Rafael could be threatening and remind us of the Teenage Mutant Ninja Turtles all over again, lol.


I'm a 90s kid ('91 to be exact), but I adore the TMNT. So awesome.
Member Since: March 7, 2007 Posts: 552 Comments: 19871
<
Member Since: Posts: Comments:
I don't know why it's called son of Isaac?.When in all reality if it does get name it will be a she name..So daughter of Isaac sounds more fitting.
Member Since: August 14, 2010 Posts: 10 Comments: 16383
Ok maybe Valerie sounds threatening if we manage to get there.
Member Since: Posts: Comments:
Quoting windshear1993:
i just thought about the 1973 season NOT 1972..1973 why was it so inactive and it was a la nina year??

Cause the NHC was watching the Dolphins go undefeated and win back to back super bowls in '72 & '73 and obviously not paying attention to the tropics!

Ever since the Dolphins starting stinking the tropics have been going thru an "active" period. It all makes sense....right?
Member Since: Posts: Comments:
SPECIAL WEATHER STATEMENT
MSZ048-049-052340-
RANKIN MS-HINDS MS-
611 PM CDT WED SEP 5 2012

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE JACKSON MS
611 PM CDT WED SEP 5 2012

...STRONG THUNDERSTORM NEAR BYRAM...

A STRONG THUNDERSTORM CAPABLE OF PRODUCING 40 TO 50 MPH WINDS WAS
LOCATED OVER BYRAM AT 611 PM CDT...MOVING SOUTH AT 5 MPH.

PEOPLE IN EAST CENTRAL HINDS AND WEST CENTRAL RANKIN COUNTIES SHOULD
MONITOR THIS STORM CLOSELY.

LAT...LON 3207 9012 3208 9035 3233 9034 3233 9013
TIME...MOT...LOC 2311Z 359DEG 6KT 3217 9023

$$
Member Since: August 6, 2011 Posts: 4 Comments: 36847
Quoting GTcooliebai:
To be honest with you none of the names left on the list sound threatening, at least to me. When I think of Oscar I think of the Oscar Awards.

Rafael could be threatening and remind us of the Teenage Mutant Ninja Turtles all over again, lol.
Member Since: Posts: Comments:
Quoting washingtonian115:
The heat content in the gulf is way more different than it is now.

Yep, I feel more like I do today than I did yesterday.
Member Since: Posts: Comments:
Quoting KoritheMan:


I'm one of them. What's your point? :P


LOL!! I have been known to be...only on occasion...and only when justified of course :)
Member Since: Posts: Comments:
Quoting wxchaser97:
I think Michael will be a hurricane soon.
I think is one now.
Member Since: October 15, 2011 Posts: 0 Comments: 3996
Quoting OcnGypZ:


Nornmally, no.. but then there's Oscar the Grouch..........................

I would love a menacing hurricane named Oscar, lol. Then I could have fun labeling it "Oscar the Greouch" and post pics of that Sesame Street character:)
Member Since: Posts: Comments:
Member Since: August 6, 2011 Posts: 4 Comments: 36847
i just thought about the 1973 season NOT 1972..1973 why was it so inactive and it was a la nina year??
Member Since: Posts: Comments:
I think Michael will be a hurricane soon.
Member Since: March 16, 2012 Posts: 127 Comments: 7927
Quoting washingtonian115:
The heat content in the gulf is way more different than it is now.
it sure is i forgot about the upwelling isaac did lol
Member Since: Posts: Comments:
Quoting icmoore:


There's a few of those here :)


I'm one of them. What's your point? :P
Member Since: March 7, 2007 Posts: 552 Comments: 19871
Quoting 954FtLCane:
at 440 hours Karen's ghostly remains are in the Carribean heading towards the Caymans..... just crazy I tell you.

Where is WKC when you need him...
Member Since: Posts: Comments:

Viewing: 674 - 624

Page: 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 | 16 | 17 | 18 | 19 | 20 | 21 | 22 | 23 | 24 | 25 | 26 | 27 | 28Blog Index

Top of Page

About

Jeff co-founded the Weather Underground in 1995 while working on his Ph.D. He flew with the NOAA Hurricane Hunters from 1986-1990.