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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1008. angiest
Quoting Neapolitan:
Weather Historian Christopher Burt has an excellent blog post on dew point temps. Talk about some very uncomfortable humidity:

"The absolute highest dew point recorded in the region and therefore the world (of which I am aware) was 95.F at Dhahran, Saudi Arabia at 3 p.m. on July 8, 2003. The dry bulb temperature stood at 108.F at the time, so theoretically the heat index was 176.F. Sharjah in the United Arab Emirates (UAE) apparently once recorded a dew point of 93.2.F (date unknown) according to 'Weather Climate Extremes' Army Corps of Engineers TEC-0099 report."


I can't fathom how air that moist got so hot.

If the air had been dry, wow, how high could the temp have gotten.
Member Since: August 26, 2006 Posts: 16 Comments: 4766
High heat and humidity is a fact of life in the tropics. 94 degrees of heat and 96% humidity is pretty common here from June/July until November.

We use airconditioning for everything, from the home to your car and then into work. Very little time is spent outside in the elements during the work week unless it can't be helped.
Member Since: August 19, 2006 Posts: 0 Comments: 15671
Quoting TropicalAnalystwx13:


No, remember, on the behalf of Presslord, it is now known as Pressolina.

Sorry about the confusion.


I was just teasing you! Pressolina it is, back to top 5.
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1005. pottery
Quoting kmanislander:


It would appear that we are in another 3 days of relative calm after which I expect a ramping up of activity. Even very active years have spurts of activity followed by breaks where little seems to be happening. Nature has to catch its breath and we are now in one of those seemingly quiet spells after the early season run up of systems.


Well, I am complaining about lack of rain so far in Aug.
But JUNE was one of the wettest ever.
Measured rainfall on 22 days.....

Tapered off, mid July.

edited
Member Since: October 24, 2005 Posts: 0 Comments: 23099
hmmm did they drop 92L? i see no mode runs been ran tonight on it
Member Since: May 21, 2006 Posts: 5089 Comments: 114072
Weather Historian Christopher Burt has an excellent blog post on dew point temps. Talk about some very uncomfortable humidity:

"The absolute highest dew point recorded in the region and therefore the world (of which I am aware) was 95.F at Dhahran, Saudi Arabia at 3 p.m. on July 8, 2003. The dry bulb temperature stood at 108.F at the time, so theoretically the heat index was 176.F. Sharjah in the United Arab Emirates (UAE) apparently once recorded a dew point of 93.2.F (date unknown) according to 'Weather Climate Extremes' Army Corps of Engineers TEC-0099 report."
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Quoting Grothar:


Child, what it wrong with you?? The first words that babies speak in Florida isn't Mama or Papa. It's "Turn up the air-conditioning." How do you stand it without A/C in a Car. At least in my day we had covered wagons and got some air.


lol...i am in Charleston, SC...and unless my little one or husband is with me, i don't use the a/c in my vehicle...i roll the window down and open the back opera windows...been pretty hot here too...heat index in the 110+...lots of heat advisories...and i will even mow the lawn in the middle of the day...
Member Since: September 16, 2007 Posts: 0 Comments: 3599
Quoting OceanMoan:



That is 6 places, LOL.


No, remember, on the behalf of Presslord, it is now known as Pressolina.

Sorry about the confusion.
Member Since: July 6, 2010 Posts: 109 Comments: 30283
999. SLU
Member Since: Posts: Comments:
Quoting BahaHurican:
Yeah.... hard 2 believe a Hurricane can hit that far north.... but some stuff I was looking at earlier this year was implying that SSTs are well above average up there as well, meaning water warm enough to keep a warm core system going a wee bit longer....


Catching up... been away at the theatre. :-)

I've mentioned before on this blog that at 44 north lat. I'm closer to the equator than to the North Pole. A lot of the CONUS is farther north than that. I know you don't need reminding, but others...

As to SSTs, I think they're still pretty cool in these parts. What I can say for sure is that it's currently foggy, 13 degrees C, and I'm loving it. Oh, and plenty of rain lately. Sorry, Texas.
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Quoting TropicalAnalystwx13:
My top-5 most humid places:

1.) Mississippi
2.) North Carolina/South Carolina
3.) Florida
4.) Louisiana
5.) Texas



That is 6 places, LOL.
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Quoting TropicalAnalystwx13:
My top-5 most humid places:

1.) Mississippi
2.) North Carolina/South Carolina
3.) Florida
4.) Louisiana
5.) Texas


Texas is a wee bit too big to lump in like that. he humidity falls off as you get to the Edwards Plateau (roughly, west of IH-35, but that's not a hard dividing line).
Member Since: August 26, 2006 Posts: 16 Comments: 4766
Quoting angiest:


I'm noticing trees in George Bush Park (my commute goes through there) have started dying.

Austin.. Lake Travis, native trees are dying and falling in the roads. All our irrigated non-natives... doin' fine.

Something's real wrong with that.
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Evening everyone. This has got to be the most optimistic local forecast I've seen in a while. Keep in mind our "higher rain chances" are 10-20%. And they're talking about a storm off the coast of Africa. But HEY ya never know. :)


Higher rain chances this weekend...

By Patrick Vaughn

Upper level high pressure is expected to shift west and weaken over the course of this weekend. At the same time, a trough of low pressure will move through the Mid-West. This will enhance shower/thunderstorm activity over this weekend...especially Sunday. Then, next Tuesday the upper-high will begin building over the region. Temperatures will go up, but so will rain chances again as moisture move along the eastern side of the high into our area.

In the Tropics, two areas of concern are in the far Eastern Atlantic. Both of these systems are expected to develop and could become Franklin and Gert. The first system, is further north and is forecasted by the European to be a "fish" storm...never making a landfall. However, the second may be a bit of concern as it is further south and forecasted to move just north of the Caribbean Islands. The verdict is still out on this one on whether on not it will reach the Gulf.
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Quoting pottery:

I get the picture....
Not a pretty one either!


It would appear that we are in another 3 days of relative calm after which I expect a ramping up of activity. Even very active years have spurts of activity followed by breaks where little seems to be happening. Nature has to catch its breath and we are now in one of those seemingly quiet spells after the early season run up of systems.

Member Since: August 19, 2006 Posts: 0 Comments: 15671
Quoting Grothar:



You don't want to go there in the summer. I have been many times and it is incredible hot. I do not perspire, so it is much more intolerable for me. I can be out on the most hot humid day and I am dry as a bone. (And if you make a wise-crack......)

An OLD bone thats been on the driveway for months....
No wisecracks needed, by him......
Member Since: October 24, 2005 Posts: 0 Comments: 23099
This weekend I will be making *another* trip to Dallas. My normal route takes me past Lake Somerville. I will try to take a detour and go over the dam and hopefully get some pictures. The lake is likely to be below 50% capacity by that time.
Member Since: August 26, 2006 Posts: 16 Comments: 4766
AT LONG LAST
No rain :D
Member Since: July 7, 2010 Posts: 0 Comments: 5521
Quoting debrisball:
DFW airport 100 degree days streak ends at 40, just 2 days shy of the 1980 record, that line of storms fell apart just before it reached the area, the high was 97 at about 1:00 before the clouds rolled in cooled temps to the mid 80s early this afternoon but not a drop of rain reached the ground. Now we know what Mike Mussina getting a perfect game broken up with 2 outs in the 9th with a cheap bloop hit by Carl Everett must have felt like, getting robbed of such an illustrious record after being oh so close.

On the other hand, Wichita Falls--which isn't so many miles from Dallas--reached 100 today, the 51st consecutive day (and 70th of the last 71) to do so. (The previous record of 42 consecutive days fell last week). The most telling record, however, is this: before this year, Amarillo's record for 100-degree days in a single year was 26. It's so far happened 39 times in 2011. (The average, by the way, is six.)
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My top-5 most humid places:

1.) Mississippi
2.) Pressolina
3.) Florida
4.) Louisiana
5.) Texas
Member Since: July 6, 2010 Posts: 109 Comments: 30283
Quoting thunderbug91:



Central FL is BRUTAL right now! Take it from a guy stuck in heavy traffic with no car AC.....


Child, what it wrong with you?? The first words that babies speak in Florida isn't Mama or Papa. It's "Turn up the air-conditioning." How do you stand it without A/C in a Car. At least in my day we had covered wagons and got some air.
Member Since: July 17, 2009 Posts: 64 Comments: 23744
985. txjac
Take it from a guy stuck in heavy traffic with no car AC.....


I gave you a + because of your broken AC ..that bites
Member Since: April 24, 2010 Posts: 1 Comments: 2357
As of tomorrow, it will have been 200 days since the City of Houston has recorded a single day rain total of at least 1 inch. The longest such spell in the city's history.
Member Since: August 26, 2006 Posts: 16 Comments: 4766
Quoting MississippiWx:
I am happy any part of Texas gets any rain even though it is 200 miles from me, some places in Texas got a little rain today, hearing half an inch in some places if no more
Member Since: July 5, 2009 Posts: 0 Comments: 1348
Quoting twincomanche:
I have never been in the Mid East with their outrageous temperatures but have been in the American South West in the one hundred teens and Oklahoma and Texas in the hundreds and been in Florida and Puerto Rico with mid nineties and very high humidity and I think from a comfort level the hot dry is more tolerable than the lower temps with high humidity. Just my personal observations.



You don't want to go there in the summer. I have been many times and it is incredible hot. I do not perspire, so it is much more intolerable for me. I can be out on the most hot humid day and I am dry as a bone. (And if you make a wise-crack......)
Member Since: July 17, 2009 Posts: 64 Comments: 23744
I can tolerate a dry heat, like 100 degrees and little humidity, more than I can tolerate 95 degrees and lots of humidity, and I live in South Florida. Last summer here, one day it read 102 and the heat index was 120 or so. It's downright awful. I played 27 holes of golf on a 102 degree day in inland South Carolina, before it became unbearable. Down here, by the time you got to the back nine on a day like that, you would stop there on the spot.
Member Since: October 8, 2008 Posts: 14 Comments: 4553
93L is so big that it is eating up 92L tonight in fac 92L looks like a open wave tonight
Member Since: May 21, 2006 Posts: 5089 Comments: 114072
Quoting Grothar:


Depends on what part. Central and Northern Florida can be brutal in the summer. I mean we are not Death Valley, but it depends on where one is in Florida. The more South you are the milder the summer. It can be very humid here at times. But I have been to Georgia and Louisiana in the summer and it was much more humid there.



Central FL is BRUTAL right now! Take it from a guy stuck in heavy traffic with no car AC.....
Member Since: June 23, 2010 Posts: 0 Comments: 583
Quoting kmanislander:


I'm sure that didn't stop them from visiting the soft serve icecream stations on deck LMAO.

I get the picture....
Not a pretty one either!
Member Since: October 24, 2005 Posts: 0 Comments: 23099
Quoting pottery:

LOL...
But seriously, I visited Arizona when the Temps were low hundreds.
Low humidity, and I had no problem with that.
Here it has been mid 90's all week with Humidity in the 70-80 range.

You FEEL that...


yeah...it is like walking into the bathroom with the door shut after someone has been taking a very hot shower for like 20 minutes...it is enuf to slap you right in the face...
Member Since: September 16, 2007 Posts: 0 Comments: 3599
Quoting tiggeriffic:


i know right?! but if it holds true then we will be fine, theory says that who ever is in the path in the first days are safe when it actually makes landfall.... just hoping it is true lol


That is what I keep telling my son. He gets on here sometimes to see whats going on and he saw that run. :-)
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972. txjac
Quoting pottery:

LOL...
But seriously, I visited Arizona when the Temps were low hundreds.
Low humidity, and I had no problem with that.
Here it has been mid 90's all week with Humidity in the 70-80 range.

You FEEL that...


I know exactly what you mean pot ...grew up in Ohio and had no problem with the cold there ...have issues with the cold here because of the humidity
Member Since: April 24, 2010 Posts: 1 Comments: 2357
Quoting tiggeriffic:


i know right?! but if it holds true then we will be fine, theory says that who ever is in the path in the first days are safe when it actually makes landfall.... just hoping it is true lol


I wouldn't worry.
Member Since: August 27, 2006 Posts: 0 Comments: 1664
Quoting pottery:

LOL
Or swinging a Golf Club...
The passengers on the cruise boats must have been horrified at the weather!


I'm sure that didn't stop them from visiting the soft serve icecream stations on deck LMAO.
Member Since: August 19, 2006 Posts: 0 Comments: 15671
Quoting txjac:


lol ...love it ...is that anything like a wet cold?


Actually we say "a damp cold"...lol..but whether it is a blistering dry heat or a sultry humid heat, both are hard on ya.~~~~ dizzying, I say.
Member Since: September 16, 2010 Posts: 0 Comments: 1492
I have been to Las Vegas when it was above 115 and I had no problem with it, 90s in Houston, La and along gulf coast and I am like are you kidding me.
Member Since: July 5, 2009 Posts: 0 Comments: 1348
Quoting bohonkweatherman:
I have been told by people that have gone to Florida that their humidity is off the charts? I have been to Georgia, La and South Carolina and their humidity was worse than here in Texas. Am I wrong about Florida?


Depends on what part. Central and Northern Florida can be brutal in the summer. I mean we are not Death Valley, but it depends on where one is in Florida. The more South you are the milder the summer. It can be very humid here at times. But I have been to Georgia and Louisiana in the summer and it was much more humid there.
Member Since: July 17, 2009 Posts: 64 Comments: 23744
Quoting OceanMoan:


That is an unsettling image!


i know right?! but if it holds true then we will be fine, theory says that who ever is in the path in the first days are safe when it actually makes landfall.... just hoping it is true lol
Member Since: September 16, 2007 Posts: 0 Comments: 3599
964. beell
Quoting twincomanche:
I personally bet not. I think this thing is about to break We shall see.


ECMWF and GFS bring 500mb heights of 594 decameters over Texas next week. That is stronger than it is now. It may moderate some to the north (central plains) but I don't see a breakdown yet for us.
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Quoting bohonkweatherman:
I have been told by people that have gone to Florida that their humidity is off the charts? I have been to Georgia, La and South Carolina and their humidity was worse than here in Texas. Am I wrong about Florida?

Living in south florida for the last 13 years the humidity is bad but it could be worse. The worst part is the sticky feeling every time you go outside.
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Quoting bohonkweatherman:
I have been told by people that have gone to Florida that their humidity is off the charts? I have been to Georgia, La and South Carolina and their humidity was worse than here in Texas. Am I wrong about Florida?




No you are right about Florida. Take it from a lifelong Tampa native.... It isn't necessarily our highs (although Plant City did hit 106 several weeks ago and 100 again recently) but it is the incessant humidity.... Heat indexes are 100+ at 8:30 in the morning, no kidding.
Member Since: June 23, 2010 Posts: 0 Comments: 583
Quoting kmanislander:


LOL. Actually we got quite a bit today with lots of T & L. Purely a local event that barely showed up on satellite but very impressive to see. I witnessed several significant lightning discharges over the cruise ships in harbour and then later ( around 6 our time ) over my neighbourhood.

You certainly didn't want to be outside holding an umbrella !

LOL
Or swinging a Golf Club...
The passengers on the cruise boats must have been horrified at the weather!
Member Since: October 24, 2005 Posts: 0 Comments: 23099
DFW airport 100 degree days streak ends at 40, just 2 days shy of the 1980 record, that line of storms fell apart just before it reached the area, the high was 97 at about 1:00 before the clouds rolled in cooled temps to the mid 80s early this afternoon but not a drop of rain reached the ground. Now we know what Mike Mussina getting a perfect game broken up with 2 outs in the 9th with a cheap bloop hit by Carl Everett must have felt like, getting robbed of such an illustrious record after being oh so close.
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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.