Two African waves, 92L and 93L, worth watching

By: Dr. Jeff Masters , 2:59 PM GMT on August 11, 2011

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An African wave is near 13°N 35°W, about 700 miles west-southwest of the Cape Verde Islands. This system, (Invest 92L), is moving west to west-northwest at 10 - 15 mph, and has the potential to develop into a tropical depression or tropical storm before arriving near the northern Lesser Antilles Islands early next week. Recent visible satellite loops show that 92L has less heavy thunderstorm activity near where it is trying to develop its circulation center than yesterday. Water vapor satellite loops that a large area of dry air lies just to the west of 92L, but the atmosphere in the immediate vicinity of 92L is moist. Even so, the decline of heavy thunderstorm activity since yesterday implies that dry air is probably working its way into 92L. The SHIPS model and University of Wisconsin CIMSS wind shear analysis are showing moderate wind shear of 10 - 15 knots affecting 92L. Sea surface temperatures are 26.5° - 27°C, which is very close to the 26.5°C threshold usually needed to support a tropical storm.


Figure 1. Morning satellite photo of Invest 92L and Invest 93L.

Forecast for 92L
Low to moderate wind shear of 5 - 15 knots is predicted along 92L's path over the coming three days, which should allow the storm to organize, assuming it can shut out any incursions of dry air that might intrude. The latest 00Z and 06Z model runs of the four best models for predicting tropical storm formation (GFS, ECMWF, NOGAPS, and UKMET) show weak development or no development of 92L, and NHC gave 92L a 30% chance of developing into a tropical depression by Saturday morning in their 8am outlook. A steady west to west-northwest motion for 92L is predicted by all of the models, which would put the storm in the vicinity of the northern Lesser Antilles Islands by Sunday. On Saturday and Sunday, 92L is expected to enter a region where an upper-level low pressure system will bring high wind shear of 20 knots to the storm, which should slow development. This upper-level low is also expected to turn 92L more to the northwest, so the storm is likely to pass north of the Lesser Antilles, though may pass close enough to give heavy rains to the northernmost islands. It is too early to know if 92L will recurve out to sea and potentially threaten Bermuda, or continue to the northwest towards the U.S. East Coast.

93L
An African wave that emerged off the coast of Africa is near 10°N 22°W, a few hundred miles south of the Cape Verde Islands. This system, (Invest 93L), is also moving west at 10 - 15 mph, and has the potential to develop into a tropical depression or tropical storm before arriving near the northern Lesser Antilles Islands near the middle of next week. Recent visible satellite loops show that 93L has a decent amount of heavy thunderstorms, but this activity is not well organized. There is not much spin associated with 93L yet. 93L is fairly well-protected from dry air to its north and west. The SHIPS model and University of Wisconsin CIMSS wind shear analysis are showing moderate wind shear of 10 - 20 knots affecting 93L. Sea surface temperatures are 27.5°C, which is one degree above the 26.5°C threshold usually needed to support a tropical storm.

Forecast for 93L
Moderate wind shear below 20 knots is predicted along 93L's path over the coming five days, which should allow the storm to steadily organize. 93L is about 600 miles east of 92L, which is close enough that the two systems may interfere with each others' organization. The latest 00Z and 06Z model runs of the four best models for predicting tropical storm formation (GFS, ECMWF, NOGAPS, and UKMET), have only one model, the GFS, that is indicating significant development of 93L. This model brings 93L near the northern Lesser Antilles Islands by Wednesday. NHC gave 93L a 20% chance of developing into a tropical depression by Saturday morning in their 8am outlook. Due to moister air, the potential for less wind shear, and a more southerly track, 93L is probably a greater threat to the Lesser Antilles than 92L.

Jeff Masters

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1409. JLPR2
Each circle is to the NW of the other.

Lots of disturbances out there.
Member Since: September 4, 2007 Posts: 7 Comments: 8483
Quoting MiamiHurricanes09:
Welcome to hurricane season.


My favorite time of year. Or not, depending on how you look at it. I can't get off the blog during such a time. ;)
Member Since: Posts: Comments:
Quoting Stormchaser2007:
Could be 94L

SHOWER ACTIVITY ASSOCIATED WITH A TROUGH OF LOW PRESSURE ABOUT
250 MILES WEST-NORTHWEST OF BERMUDA HAS BECOME A LITTLE BETTER
ORGANIZED DURING THE PAST SEVERAL HOURS. ADDITIONAL SLOW
DEVELOPMENT IS POSSIBLE DURING THE NEXT DAY OR SO BEFORE THIS
DISTURBANCE MERGES WITH A FRONTAL SYSTEM. THIS SYSTEM HAS A LOW
CHANCE...20 PERCENT...OF BECOMING A TROPICAL CYCLONE DURING THE
NEXT 48 HOURS AS IT MOVES NORTHEASTWARD AT 15 TO 20 MPH.




then may see 95L has well
Member Since: May 21, 2006 Posts: 5091 Comments: 114649
sorry I meant 10%,20%,30%,40%

000
ABNT20 KNHC 120536
TWOAT

TROPICAL WEATHER OUTLOOK
NWS NATIONAL HURRICANE CENTER MIAMI FL
200 AM EDT FRI AUG 12 2011

FOR THE NORTH ATLANTIC...CARIBBEAN SEA AND THE GULF OF MEXICO...

A BROAD AREA OF LOW PRESSURE CENTERED ABOUT 1000 MILES WEST OF
THE SOUTHERN CAPE VERDE ISLANDS IS MOVING WESTWARD AT NEAR 15 MPH.
THE ASSOCIATED SHOWER ACTIVITY REMAINS DISORGANIZED...AND SATELLITE
IMAGERY SUGGESTS THE SYSTEM MAY CURRENTLY BE ENCOUNTERING A DRIER
AND MORE STABLE AIR MASS. HOWEVER...ENVIRONMENTAL CONDITIONS ARE
EXPECTED TO BECOME MORE FAVORABLE FOR DEVELOPMENT DURING THE NEXT
SEVERAL DAYS. THIS SYSTEM HAS A MEDIUM CHANCE...30 PERCENT...OF
BECOMING A TROPICAL CYCLONE DURING THE NEXT 48 HOURS.

A LOW PRESSURE SYSTEM LOCATED ABOUT 275 MILES SOUTH-SOUTHWEST OF THE
SOUTHERN CAPE VERDE ISLANDS IS PRODUCING A LARGE AREA OF CLOUDINESS
AND SCATTERED THUNDERSTORMS. ENVIRONMENTAL CONDITIONS ARE EXPECTED
TO GRADUALLY BECOME MORE CONDUCIVE FOR DEVELOPMENT OVER THE NEXT
SEVERAL DAYS AS IT MOVES WESTWARD AT 15 TO 20 MPH. THIS SYSTEM HAS
A MEDIUM CHANCE...40 PERCENT...OF BECOMING A TROPICAL CYCLONE
DURING THE NEXT 48 HOURS.

SHOWER ACTIVITY ASSOCIATED WITH A TROUGH OF LOW PRESSURE ABOUT
250 MILES WEST-NORTHWEST OF BERMUDA HAS BECOME A LITTLE BETTER
ORGANIZED DURING THE PAST SEVERAL HOURS. ADDITIONAL SLOW
DEVELOPMENT IS POSSIBLE DURING THE NEXT DAY OR SO BEFORE THIS
DISTURBANCE MERGES WITH A FRONTAL SYSTEM. THIS SYSTEM HAS A LOW
CHANCE...20 PERCENT...OF BECOMING A TROPICAL CYCLONE DURING THE
NEXT 48 HOURS AS IT MOVES NORTHEASTWARD AT 15 TO 20 MPH.

AN AREA OF DISTURBED WEATHER HAS FORMED IN ASSOCIATION WITH A BROAD
LOW PRESSURE AREA ABOUT 800 MILES NORTHEAST OF THE NORTHERN LEEWARD
ISLANDS. SLOW DEVELOPMENT IS POSSIBLE DURING THE NEXT COUPLE OF
DAYS AS THE LOW MOVES WEST-SOUTHWESTWARD AT ABOUT 10 MPH. THIS
SYSTEM HAS A LOW CHANCE...10 PERCENT...OF BECOMING A TROPICAL
CYCLONE DURING THE NEXT 48 HOURS.

ELSEWHERE...TROPICAL CYCLONE FORMATION IS NOT EXPECTED DURING THE
NEXT 48 HOURS.

Member Since: Posts: Comments:
Could be 94L

SHOWER ACTIVITY ASSOCIATED WITH A TROUGH OF LOW PRESSURE ABOUT
250 MILES WEST-NORTHWEST OF BERMUDA HAS BECOME A LITTLE BETTER
ORGANIZED DURING THE PAST SEVERAL HOURS. ADDITIONAL SLOW
DEVELOPMENT IS POSSIBLE DURING THE NEXT DAY OR SO BEFORE THIS
DISTURBANCE MERGES WITH A FRONTAL SYSTEM. THIS SYSTEM HAS A LOW
CHANCE...20 PERCENT...OF BECOMING A TROPICAL CYCLONE DURING THE
NEXT 48 HOURS AS IT MOVES NORTHEASTWARD AT 15 TO 20 MPH.
Member Since: Posts: Comments:
Welcome to hurricane season.
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Quoting wunderkidcayman:
hmm 10%,10%,30%,40%




funny has it seen but its 10 20 30 and 40%
Member Since: May 21, 2006 Posts: 5091 Comments: 114649
hmm 10%,10%,30%,40%
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would t it be funny if all 4 be came a name storm on the two lol
Member Since: May 21, 2006 Posts: 5091 Comments: 114649
New AOI? Interesting.
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1398. Gearsts
Quoting sunlinepr:

Monzon made a good analysis, taking in consideration 93L, that 92L was making the way for it to develop, eating all the dry air and SAL and the fact that 93L is in a more S track, where the SST is warmer...
93L me recuerda a Georges en todo y eso no es bueno.Tambien vi las noticias y Ada habla mucho sobre 93L con preocupacion, ella sabe mas q todo nosotros :)
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TROPICAL WEATHER OUTLOOK
NWS NATIONAL HURRICANE CENTER MIAMI FL
200 AM EDT FRI AUG 12 2011

FOR THE NORTH ATLANTIC...CARIBBEAN SEA AND THE GULF OF MEXICO...

A BROAD AREA OF LOW PRESSURE CENTERED ABOUT 1000 MILES WEST OF
THE SOUTHERN CAPE VERDE ISLANDS IS MOVING WESTWARD AT NEAR 15 MPH.
THE ASSOCIATED SHOWER ACTIVITY REMAINS DISORGANIZED...AND SATELLITE
IMAGERY SUGGESTS THE SYSTEM MAY CURRENTLY BE ENCOUNTERING A DRIER
AND MORE STABLE AIR MASS. HOWEVER...ENVIRONMENTAL CONDITIONS ARE
EXPECTED TO BECOME MORE FAVORABLE FOR DEVELOPMENT DURING THE NEXT
SEVERAL DAYS. THIS SYSTEM HAS A MEDIUM CHANCE...30 PERCENT...OF
BECOMING A TROPICAL CYCLONE DURING THE NEXT 48 HOURS.

A LOW PRESSURE SYSTEM LOCATED ABOUT 275 MILES SOUTH-SOUTHWEST OF THE
SOUTHERN CAPE VERDE ISLANDS IS PRODUCING A LARGE AREA OF CLOUDINESS
AND SCATTERED THUNDERSTORMS. ENVIRONMENTAL CONDITIONS ARE EXPECTED
TO GRADUALLY BECOME MORE CONDUCIVE FOR DEVELOPMENT OVER THE NEXT
SEVERAL DAYS AS IT MOVES WESTWARD AT 15 TO 20 MPH. THIS SYSTEM HAS
A MEDIUM CHANCE...40 PERCENT...OF BECOMING A TROPICAL CYCLONE
DURING THE NEXT 48 HOURS.

SHOWER ACTIVITY ASSOCIATED WITH A TROUGH OF LOW PRESSURE ABOUT
250 MILES WEST-NORTHWEST OF BERMUDA HAS BECOME A LITTLE BETTER
ORGANIZED DURING THE PAST SEVERAL HOURS. ADDITIONAL SLOW
DEVELOPMENT IS POSSIBLE DURING THE NEXT DAY OR SO BEFORE THIS
DISTURBANCE MERGES WITH A FRONTAL SYSTEM. THIS SYSTEM HAS A LOW
CHANCE...20 PERCENT...OF BECOMING A TROPICAL CYCLONE DURING THE
NEXT 48 HOURS AS IT MOVES NORTHEASTWARD AT 15 TO 20 MPH.

AN AREA OF DISTURBED WEATHER HAS FORMED IN ASSOCIATION WITH A BROAD
LOW PRESSURE AREA ABOUT 800 MILES NORTHEAST OF THE NORTHERN LEEWARD
ISLANDS. SLOW DEVELOPMENT IS POSSIBLE DURING THE NEXT COUPLE OF
DAYS AS THE LOW MOVES WEST-SOUTHWESTWARD AT ABOUT 10 MPH. THIS
SYSTEM HAS A LOW CHANCE...10 PERCENT...OF BECOMING A TROPICAL
CYCLONE DURING THE NEXT 48 HOURS.

ELSEWHERE...TROPICAL CYCLONE FORMATION IS NOT EXPECTED DURING THE
NEXT 48 HOURS.

$$
Member Since: May 21, 2006 Posts: 5091 Comments: 114649
Good 4 you! Things may be changing!
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Quoting swflurker:
Texas is getting some rain?


We got some where I live this afternoon. Too bad it was just enough to raise the humidity and make it feel hotter.
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Texas is getting some rain?
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i know gfs and euro,just thought it was interestung its done well with her so far
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Quoting Jedkins01:
St. Petersburg, Whitted Airport
Lat: 27.77 Lon: -82.63 Elev: 8
Last Update on Aug 12, 12:53 am EDT

A Few Clouds

84 °F
(29 °C)
Humidity: 91 %
Wind Speed: SW 3 MPH
Barometer: 29.90" (1012.3 mb)
Dewpoint: 81 °F (27 °C)
Heat Index: 98 °F (37 °C)
Visibility: 10.00 mi.
More Local Wx: 3 Day History:
,been darn hot down here in sarasota at night lately,no relief unless you go inside,even the gom over 90 nearshore
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Quoting stillwaiting:
,didvyou see thevlatest nam run???,very interestingbto say the least,she may come back to fl to pay another visit!
Yeah lol, but keep in mind it is just the NAM. Not really a tropical model.
Member Since: August 12, 2007 Posts: 11 Comments: 2448
Quoting SouthDadeFish:
They said the same thing for Emily...
,didvyou see thevlatest nam run???,very interestingbto say the least,she may come back to fl to pay another visit!
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Quoting Tropicsweatherpr:


Yes,Ada Monzon,Deborah Martorell and Roberto Cortes have been talking about the Eastern Atlantic systems. I am sure that even more analysis by then will occur as the days pass.

Monzon made a good analysis, taking in consideration 93L, that 92L was making the way for it to develop, eating all the dry air and SAL and the fact that 93L is in a more S track, where the SST is warmer...
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Quoting KoritheMan:


And she did in fact, come perilously close to Florida.
Well I think "perilously" makes her sound way worse than she was ;~) If she had remained intact I think she would have gone slightly farther east. It was a pretty remarkable trough for the time of the year.
Member Since: August 12, 2007 Posts: 11 Comments: 2448
Quoting gugi182:
Writing from Puerto Rico down here we are starting to watch the progress of 93L in the local news but not worrying to much as for 92L.


Sabremos lo serio que sera el Domingo o lunes... Mientras no compro poteria, ni pongo tormenteras...

Sunday will be the day to know what to do...
Member Since: Posts: Comments:
Also, one thing to remember is that last year, the start of the recurves came with Danielle. She was exceptionally large, powerful, and slow moving. A combination of those factors helped to reinvigorate a preexisting weakness within the Atlantic ridge along 70W, which paved the way for Earl's subsequent recurvature.

At the moment, it's looking more likely that 93L will become the dominant system, as 92L is looking rather dismal. It may develop further down the road, but even if it does, the prospects of it becoming a significant hurricane are diminishing.

Without such a strong storm to reinforce the slackened ridge prior to a secondary storm following roughly the same trajectory, the prospects for recurvature may not be as high as they were with Earl.

Just food for thought.
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Quoting gugi182:
Writing from Puerto Rico down here we are starting to watch the progress of 93L in the local news but not worrying to much as for 92L.


Yes,Ada Monzon,Deborah Martorell and Roberto Cortes have been talking about the Eastern Atlantic systems. I am sure that even more analysis by then will occur as the days pass.
Member Since: April 29, 2009 Posts: 75 Comments: 13926
1384. gugi182
Writing from Puerto Rico down here we are starting to watch the progress of 93L in the local news but not worrying to much as for 92L.
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Quoting SouthDadeFish:
They said the same thing for Emily...


And she did in fact, come perilously close to Florida.
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St. Petersburg, Whitted Airport
Lat: 27.77 Lon: -82.63 Elev: 8
Last Update on Aug 12, 12:53 am EDT

A Few Clouds

84 °F
(29 °C)
Humidity: 91 %
Wind Speed: SW 3 MPH
Barometer: 29.90" (1012.3 mb)
Dewpoint: 81 °F (27 °C)
Heat Index: 98 °F (37 °C)
Visibility: 10.00 mi.
More Local Wx: 3 Day History:
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1381. Gearsts
Quoting Tazmanian:
here what am thinking


92L 20%

93L 60%


40% 40%
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Quoting hunkerdown:
Emily pulled out around the periphery of a high, not due to a trough.
oh really?

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here what am thinking


92L 20%

93L 60%


Member Since: May 21, 2006 Posts: 5091 Comments: 114649
Does anyone has the 00z NOGAPS?
Member Since: April 29, 2009 Posts: 75 Comments: 13926
1377. gugi182
Watching 93L at the 2am update NHC what do you guys give it more than 40%.
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when the new two comes out am going to bed
Member Since: May 21, 2006 Posts: 5091 Comments: 114649
Quoting SouthDadeFish:
They said the same thing for Emily...
Emily pulled out around the periphery of a high, not due to a trough.
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1372. rv1pop
Quoting HuracanTaino:
Same happened to me 2 days ,withour power do to "the Moca Tornado" that you probably heard" about in the local news, with an storm or a hurricane I don't want to imagine what would happen ....
I probably should do a blog on emergency power, but real quickly, a good deep cycle battery (marine starter might be best for the occasional user) along with a 400 watt / 800 watt surge inverter would be a sound investment for emergencies. It would be about the same price as the horrible UPS's you can get from the computer or big box stores. It is not a ups so it is not a standby unit, but if you are using a laptop, you can get hours of computer use from it. The smaller CFL light bulbs can run for many hours from it. I use 2 of the batteries in parallel with this set up and can get about 6 hours or so of light and laptop before I start the car up and hook up jumper cables to re-charge the batteries in 20 to 30 minutes or less depending on the alternator (9 minutes in the motorhome with the police alternator(120 Amp.)) HTH POP
Member Since: August 18, 2007 Posts: 0 Comments: 191
Quoting reedzone:
It doesn't make sense.. This is August, not October.. Trough should be weaker then what the model is showing.
They said the same thing for Emily...
Member Since: August 12, 2007 Posts: 11 Comments: 2448
Quoting reedzone:
It doesn't make sense.. This is August, not October.. Trough should be weaker then what the model is showing.
GFS = trough enhancer
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Well, we'll find out what the future for 92L and/or 93L in few days. I'll be back in couple of days to discuss about this system.
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Quoting Stormchaser2007:
Things seem rather quiet for now after 92L and 93L.

MJO favors the WATL, but there is no support for development yet. Just seems to be the EPAC.

seems to be some healthy waves over Africa, sic 1234. On the last page, I believe sunlinepr posted a sat of Africa that had a train of healthy waves. Will have to see what/how things really pan out.
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1366. LBAR
Looks like 92L is starting to pull away from 93L. 93L being slowed by the next wave pulling the flow back towards Africa?
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Other weather news: apparently an EF-0 tornado struck Wilson County in North Carolina according to my friends at NWS Raleigh on August 6th. We needed rain, but not another tornadoic thunderstorms (April 16 was enough, thank you).
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Quoting Tazmanian:




plzs dont Quote him many of us have him on Ignore
I know but a lot don't. To be honest, there are many who do not stockpile names on an ignore list. There is no harm seeing everyone's posts, hell, it can be very amusing. All it take is a little hootzpa to not let it get to you.
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It doesn't make sense.. This is August, not October.. Trough should be weaker then what the model is showing.
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Complete Update

TS BUSTED FORECAST ALIBI





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Things seem rather quiet for now after 92L and 93L.

MJO favors the WATL, but there is no support for development yet. Just seems to be the EPAC.

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Quoting JFV2013:


How'd you know? :0.
this blog knows all...or maybe it was a paid site :)
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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.