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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1159. JLPR2
Quoting MississippiWx:


Eh, you just took the words right out of my mouse. :-p I was about to post the same thing.


You have a mouse there? Need a cat to catch it? XD
Member Since: Posts: Comments:
Quoting robj144:


That is was the worst spelling of the word "central" I've ever seen. :) Unless that is some weird acronym I'm not aware of...


Stands for East Central.
Member Since: July 15, 2006 Posts: 17 Comments: 10284
1157. robj144
Quoting angiest:


east central I think.


That would be better than.
Member Since: August 19, 2008 Posts: 0 Comments: 825
In 84 hours, the 00z NAM tries to develop the part that split off Emily and headed south around the Eastern periphery of the Bermuda Ridge. Just something to humor you while waiting on the 00z GFS:

Member Since: July 15, 2006 Posts: 17 Comments: 10284
Quoting Tazmanian:
hey guys can we plzs get back too 92 and 93L
Relax Taz, nothing is changing by the minute, or even by the hour.
Member Since: Posts: Comments:
1154. angiest
Quoting robj144:


That is was the worst spelling of central I've ever seen. :) Unless that is some weird acronym I'm not aware of...


east central I think.
Member Since: August 26, 2006 Posts: 16 Comments: 4766
1153. robj144
Quoting WeatherfanPR:
Sorry if someone did a copy n paste of this earlier.

Area forecast discussion...corrected
National Weather Service San Juan PR
915 PM AST Thursday Aug 11 2011


Synopsis...subtropical ridge will remain the dominant weather feature
into next week. Two areas of low pressure across the ecntrl Atlantic may
become tropical cyclones over the next several days and could approach
the region early to middle part of next week.


&&


Discussion...dense fog noted earlier this evening on 11-3.9
micron imagery across the southern slopes from Maricao east to Jayuya but
seems to have improved somewhat more recently. Also high clouds
moving from the east may prevent additional fog formation overnight.


Things look pretty quiet and stable next few days
with just isolated afternoon convection across western PR. Model
fields of 850 mb thetae all show a decline over the weekend while k
index and precipitable water remain nearly steady. Model guidance now suggests a
weaker TUTT will move across the area over the weekend with
subtropical ridge holding stronger.


Next week...forecast will hinge on track of two areas of low pressure
across the ecntrl Atlantic. First low (invest 92l) looking less
organized as discussed in latest tropical weather outlook. Some models
actually do not give this system much chance of development with
the reliable European model (ecmwf) and GFDL just showing an open trough.


Invest 93l looking more impressive with a more concentrated area
of thunderstorms. This system is looking more likely that it will
eventually become a named system over the weekend. HPC/NHC
coordination indicating this system taking a more westward track with
HPC dy3-dy7 extended graphics indicating a tropical cyclone just
south of Saint Croix by 12z Thursday Aug 18. The 12z European model (ecmwf) (the top
performer over the past three years) shows system tracking between
St. John and Anegada island next Thursday with the second most reliable
model the GFDL taking it rather briskly across Martinique Tuesday
evening. So some notable differences seen here in track/timing of any
potential impacts. For now the HPC/NHC and European model (ecmwf) solutions look
much better as they match up better with climatology.


That is was the worst spelling of the word "central" I've ever seen. :) Unless that is some weird acronym I'm not aware of...
Member Since: August 19, 2008 Posts: 0 Comments: 825
1152. Grothar
Quoting atmoaggie:
After a fight over the file size on the image hosting sites...

I think someone was hoping to see a loop of yesterday's 18 Z GFS posted.



I did have truncate off the first 178 hours and resample to get it under the hosting services' file size limits.


I think you shrunk your link too much. All I see is a red X.
Member Since: Posts: Comments:
Quoting WeatherfanPR:
Sorry if someone did a copy n paste of this earlier.

Area forecast discussion...corrected
National Weather Service San Juan PR
915 PM AST Thursday Aug 11 2011


Synopsis...subtropical ridge will remain the dominant weather feature
into next week. Two areas of low pressure across the ecntrl Atlantic may
become tropical cyclones over the next several days and could approach
the region early to middle part of next week.


&&


Discussion...dense fog noted earlier this evening on 11-3.9
micron imagery across the southern slopes from Maricao east to Jayuya but
seems to have improved somewhat more recently. Also high clouds
moving from the east may prevent additional fog formation overnight.


Things look pretty quiet and stable next few days
with just isolated afternoon convection across western PR. Model
fields of 850 mb thetae all show a decline over the weekend while k
index and precipitable water remain nearly steady. Model guidance now suggests a
weaker TUTT will move across the area over the weekend with
subtropical ridge holding stronger.


Next week...forecast will hinge on track of two areas of low pressure
across the ecntrl Atlantic. First low (invest 92l) looking less
organized as discussed in latest tropical weather outlook. Some models
actually do not give this system much chance of development with
the reliable European model (ecmwf) and GFDL just showing an open trough.


Invest 93l looking more impressive with a more concentrated area
of thunderstorms. This system is looking more likely that it will
eventually become a named system over the weekend. HPC/NHC
coordination indicating this system taking a more westward track with
HPC dy3-dy7 extended graphics indicating a tropical cyclone just
south of Saint Croix by 12z Thursday Aug 18. The 12z European model (ecmwf) (the top
performer over the past three years) shows system tracking between
St. John and Anegada island next Thursday with the second most reliable
model the GFDL taking it rather briskly across Martinique Tuesday
evening. So some notable differences seen here in track/timing of any
potential impacts. For now the HPC/NHC and European model (ecmwf) solutions look
much better as they match up better with climatology.


Eh, you just took the words right out of my mouse. :-p I was about to post the same thing.
Member Since: July 15, 2006 Posts: 17 Comments: 10284
1150. emcf30
* ATLANTIC SHIPS INTENSITY FORECAST *
* GOES AVAILABLE, OHC AVAILABLE *
* INVEST AL932011 08/12/11 00 UTC *

TIME (HR) 0 6 12 18 24 36 48 60 72 84 96 108 120
V (KT) NO LAND 25 27 31 36 39 46 54 61 70 76 82 89 93
V (KT) LAND 25 27 31 36 39 46 54 61 70 76 82 89 93
V (KT) LGE mod 25 25 26 27 28 32 38 46 57 70 82 92 100
Storm Type TROP TROP TROP TROP TROP TROP TROP TROP TROP TROP TROP TROP TROP
Member Since: Posts: Comments:
Quoting NavarreMark:


You Sir, are smarter than your peers give you credit for. LOL


LOL...Well, I've been trying for a while now to get this blog to realize that I'm always right. It's a simple concept that some just can't understand. :-D
Member Since: July 15, 2006 Posts: 17 Comments: 10284
Sorry if someone did a copy n paste of this earlier.

Area forecast discussion...corrected
National Weather Service San Juan PR
915 PM AST Thursday Aug 11 2011


Synopsis...subtropical ridge will remain the dominant weather feature
into next week. Two areas of low pressure across the ecntrl Atlantic may
become tropical cyclones over the next several days and could approach
the region early to middle part of next week.


&&


Discussion...dense fog noted earlier this evening on 11-3.9
micron imagery across the southern slopes from Maricao east to Jayuya but
seems to have improved somewhat more recently. Also high clouds
moving from the east may prevent additional fog formation overnight.


Things look pretty quiet and stable next few days
with just isolated afternoon convection across western PR. Model
fields of 850 mb thetae all show a decline over the weekend while k
index and precipitable water remain nearly steady. Model guidance now suggests a
weaker TUTT will move across the area over the weekend with
subtropical ridge holding stronger.


Next week...forecast will hinge on track of two areas of low pressure
across the ecntrl Atlantic. First low (invest 92l) looking less
organized as discussed in latest tropical weather outlook. Some models
actually do not give this system much chance of development with
the reliable European model (ecmwf) and GFDL just showing an open trough.


Invest 93l looking more impressive with a more concentrated area
of thunderstorms. This system is looking more likely that it will
eventually become a named system over the weekend. HPC/NHC
coordination indicating this system taking a more westward track with
HPC dy3-dy7 extended graphics indicating a tropical cyclone just
south of Saint Croix by 12z Thursday Aug 18. The 12z European model (ecmwf) (the top
performer over the past three years) shows system tracking between
St. John and Anegada island next Thursday with the second most reliable
model the GFDL taking it rather briskly across Martinique Tuesday
evening. So some notable differences seen here in track/timing of any
potential impacts. For now the HPC/NHC and European model (ecmwf) solutions look
much better as they match up better with climatology.
Member Since: Posts: Comments:
After a fight over the file size on the image hosting sites...

I think someone was hoping to see a loop of yesterday's 18 Z GFS posted.



I did have truncate off the first 178 hours and resample to get it under the hosting services' file size limits.
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1146. emcf30
93L Ensembles


92L Ensembles
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Quoting extreme236:
Wow 00z LGEM brings 93L up to 100kts..


Very believable, assuming the 100kts is at the end of its forecast period. It still needs a little time to establish a surface circulation.
Member Since: July 15, 2006 Posts: 17 Comments: 10284
Quoting extreme236:
Wow 00z LGEM brings 93L up to 100kts..


Do you have the link to it?
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1142. hcubed
Quoting robj144:


What is the acronym for MUD?


In Omaha, it was the Metropolitan Utilities District.
Member Since: Posts: Comments:
Quoting NavarreMark:


Please quit quoting people on my ignore list.


Lol..I think I see what you did there...

As in, you were making fun of the person being quoted because he normally says same thing you just said...

At least, I think that's what you're doing.
Member Since: July 15, 2006 Posts: 17 Comments: 10284
Wow 00z LGEM brings 93L up to 100kts..
Member Since: Posts: Comments:
1139. JLPR2
Quoting Thrawst:


I Live in Nassau, Bahamas. Beat this haha :P -

Temperature: 82 F
Dew Point: 81 F
Humidity: 94%
Heat Index: 94
Wind: Calm

... THAT is miserable :P


Your humidity is rather uncomfortable. But keep it, I don't want to match it. xD
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1137. emcf30
Quoting MississippiWx:


LOL...I tried to leave that one out, but you just had to bring it up...

My bad, just couldn't resist.
Member Since: Posts: Comments:
1136. robj144
Quoting emcf30:


1. gimp

(1) a derrogatory term for someone that is disabled or has a medicial problem that results in physical impairment.

(2) An insult implying that someone is incompetent, stupid, etc. Can also be used to imply that the person is uncool or can't/won't do what everyone else is doing.

(3) A sex slave or submissive, usually male, as popularlized by the movie Pulp Fiction.

He probably was referring to #3. LOL


A la Pulp Fiction.
Member Since: August 19, 2008 Posts: 0 Comments: 825
Quoting robj144:


Yes, I know, but Grothar wasn't hear to know it was a joke. :)


I was getting around to telling him....

He hasn't said anything in a few minutes, though. Hope he's not crying. :-|
Member Since: July 15, 2006 Posts: 17 Comments: 10284
Quoting emcf30:


1. gimp

(1) a derrogatory term for someone that is disabled or has a medicial problem that results in physical impairment.

(2) An insult implying that someone is incompetent, stupid, etc. Can also be used to imply that the person is uncool or can't/won't do what everyone else is doing.

(3) A sex slave or submissive, usually male, as popularlized by the movie Pulp Fiction.

He probably was referring to #3. LOL


LOL...I tried to leave that one out, but you just had to bring it up...
Member Since: July 15, 2006 Posts: 17 Comments: 10284
Quoting pottery:

Have not seen any....


There are model runs on here for 92l I think it's the most current. Link

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Member Since: August 2, 2010 Posts: 21 Comments: 9821
1131. Thrawst
Quoting tropicfreak:


Not sure if I even want to beat that.


nah don't even try.. unless it's like 90 degrees with a dew point of 90. I'd be happy with what I have now then...
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1130. emcf30
Quoting Grothar:


I am not familiar with that term. What does it mean?


1. gimp

(1) a derrogatory term for someone that is disabled or has a medicial problem that results in physical impairment.

(2) An insult implying that someone is incompetent, stupid, etc. Can also be used to imply that the person is uncool or can't/won't do what everyone else is doing.

(3) A sex slave or submissive, usually male, as popularlized by the movie Pulp Fiction.

He probably was referring to #3. LOL
Member Since: Posts: Comments:
Quoting robj144:


In the context of a weather blog, that would have been very hard to figure out. :)


I am a meteorologist with a water management district in Florida so I am familiar with the term...
Member Since: Posts: Comments:
1128. robj144
Quoting MississippiWx:


Lol...It's a joke...


Yes, I know, but Grothar wasn't hear to know it was a joke. :)
Member Since: August 19, 2008 Posts: 0 Comments: 825
1127. angiest
Quoting robj144:


What is the acronym for MUD?


Municipal Utility District. They are subdivisions of Texas that have the ability the issue bonds and collect propert taxes to build water and sewer facilities in unincorporated parts of the state.
Member Since: August 26, 2006 Posts: 16 Comments: 4766
Quoting Thrawst:


I Live in Nassau, Bahamas. Beat this haha :P -

Temperature: 82 F
Dew Point: 81 F
Humidity: 94%
Heat Index: 94
Wind: Calm

... THAT is miserable :P


Not sure if I even want to beat that.
Member Since: Posts: Comments:
Member Since: Posts: Comments:
Quoting robj144:


What is the acronym for MUD?


MUD = Municipal Utility District
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1123. robj144
Quoting yesterway:


MUD = Municipal Utility Districts


In the context of a weather blog, that would have been very hard to figure out. :)
Member Since: August 19, 2008 Posts: 0 Comments: 825
1122. Thrawst
Quoting JLPR2:


In Carolina, PR

Temperature 82.8 F
Heat Index 91 F
Dew Point 76 F
Humidity 81%

2hrs without power were miserable.


I Live in Nassau, Bahamas. Beat this haha :P -

Temperature: 82 F
Dew Point: 81 F
Humidity: 94%
Heat Index: 94
Wind: Calm

... THAT is miserable :P
Member Since: Posts: Comments:
Quoting robj144:


Or, in the context of how it was actually used, Gnu Image Manipulation Program.


Lol...It's a joke...
Member Since: July 15, 2006 Posts: 17 Comments: 10284
8/11 SST Anomalies...New map continues to indicate that upward motion should be concentrated in the MDR as SSTs are well above average there, while areas surrounding it are well below normal. Still a pretty good Tri-Pole setting up as well.

Member Since: July 15, 2006 Posts: 17 Comments: 10284
Quoting robj144:


What is the acronym for MUD?


MUD = Municipal Utility Districts
Member Since: Posts: Comments:
1118. robj144
Quoting MississippiWx:


Per urban dictionary:

(1) a derrogatory term for someone that is disabled or has a medicial problem that results in physical impairment.

(2) An insult implying that someone is incompetent, stupid, etc. Can also be used to imply that the person is uncool or can't/won't do what everyone else is doing.


Or, in the context of how it was actually used, Gnu Image Manipulation Program.
Member Since: August 19, 2008 Posts: 0 Comments: 825
When it rains it pours, literally.

@JimCantore
Jim Cantore
FLOODING OF A HOME IN THE 19 HUNDRED BLOCK OF 43RD STREET ALONG W/ MULTIPLE REPORTS OF STREET FLOODING ACROSS THE CITY OF LUBBOCK, TX
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Quoting Grothar:


I am not familiar with that term. What does it mean?


Per urban dictionary:

(1) a derrogatory term for someone that is disabled or has a medicial problem that results in physical impairment.

(2) An insult implying that someone is incompetent, stupid, etc. Can also be used to imply that the person is uncool or can't/won't do what everyone else is doing.
Member Since: July 15, 2006 Posts: 17 Comments: 10284
1115. bappit
.
Member Since: Posts: Comments:
1114. robj144
Quoting angiest:


According to the news last night, a local MUD has a $10,000 fine for violating watering restrictions. Didn't catch which MUD it was.


What is the acronym for MUD?
Member Since: August 19, 2008 Posts: 0 Comments: 825
1113. Grothar
Quoting MississippiWx:


Someone called you a GIMP earlier...think it was TomTaylor.

I defended you though, as I always do.


I am not familiar with that term. What does it mean?
Member Since: Posts: Comments:
1112. bappit
Quoting tropicfreak:
While 93L continues to thrive, 92L looks sickly. I think it will wait until the caribbean to develop or north of the Caribbean.


Nice pic. It's raining in the Sahel and West Texas.
Member Since: Posts: Comments:
1111. angiest
Quoting liljade:
Here in League City,Tx. we are so dry that the Resturaunts aren't allowed to serve water unless it is asked for! That's pretty bad. Can't water lawns at all,fill ponds,pools,jacuzzies fines are $500.00 per offense.Feels like we could know what Hell really does feel like. LOL


According to the news last night, a local MUD has a $10,000 fine for violating watering restrictions. Didn't catch which MUD it was.
Member Since: August 26, 2006 Posts: 16 Comments: 4766
1110. JLPR2
Quoting tiggeriffic:
temperature in Charleston 84, humidity 79%, dew point 77, heat index at 10:30pm is 93...now i am going to bed...


In Carolina, PR

Temperature 82.8 F
Heat Index 91 F
Dew Point 76 F
Humidity 81%

2hrs without power were miserable.
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1109. pottery
Quoting Tazmanian:
did they drop mode runs for 92L tonight?

Have not seen any....
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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.