African tropical wave 99L slowly organizing

By: Dr. Jeff Masters , 1:26 PM GMT on July 31, 2012

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A tropical wave (Invest 99L) near 9°N 41°W, halfway between the Lesser Antilles Islands and the coast of Africa, has the potential to develop into a tropical depression later this week as it moves westward at 10 - 15 mph. Visible satellite loops show that the disturbance now has a moderate amount of poorly-organized heavy thunderstorms that continue to slowly increase in intensity and areal coverage. There is no surface circulation, but some counter-clockwise rotation of the large-scale cloud pattern is evident. Water vapor satellite loops show that 99L has a reasonably moist environment. The latest Saharan air layer analysis shows that the dry air from the Sahara lies to the north of 99L and is currently not affecting the storm. WInd shear over the disturbance is a light 5 - 10 knots, and ocean temperatures are 28°C, (82°F) which is well above the 26.5°C (80°F) threshold typically needed to allow formation of a tropical depression.


Figure 1. Morning satellite image of Invest 99L.

Forecast for 99L
Wind shear is expected to remain light through Friday, and ocean temperatures will remain near 28°C, according to the 8 am EDT run of the SHIPS model. However, a band of high wind shear of 20 - 40 knots associated with the subtropical jet stream lies just to the north of 99L, and it would not be a surprise to see 99L experience some higher shear conditions than are currently forecast. The farther north 99L gets, the higher the shear it will experience, and the SHIPS model is predicting shear in the moderate range, 10 - 20 knots, for Saturday - Sunday, as the storm works its way to 15°N. The disturbance is at 9°N, which is close enough to the Equator that the storm will have some difficultly getting spinning. Most of the models are showing some slow development of 99L. There are some major differences in the predicted forward speed of 99L, with the ECMWF and UKMET models predicting the storm will reach the Lesser Antilles on Friday, and the GFS predicting a later arrival, on Saturday. At 8 am Tuesday, NHC gave 99L a 20% chance of developing into a tropical depression by Thursday morning. I expect the storm will begin having trouble with tendrils of dry air reaching down from the north at times this week, but give 99L a 50% chance of eventually developing into Tropical Storm Ernesto sometime in the next ten days. Residents and visitors to the Lesser Antilles Islands should anticipate heavy rains and strong winds from 99L beginning to affect the islands as early as Friday morning. The long-range fate of 99L next week is uncertain. A track west to west-northwest through the Caribbean, or to the northwest towards the U.S. East Coast are both possible. The storm is less likely to survive if it heads northwest towards the U.S.

Extreme heat in the Central U.S.
The withering heat in America's heartland continued on Monday, with high temperatures of 112° recorded in Winfield, Kansas and Searcy, Arkansas. Little Rock, Arkansas hit 111°, their 3rd hottest temperature ever record, behind the all time record of 114° set just last year on August 3, and the 112° reading of 7/31/1986. Wichita and Coffeyville in Kansas both hit 111° Monday, and in Oklahoma, Enid, Tulsa Jones Airport, and Chandler all topped out at 111°. Carr Creek, Missouri hit 110°, the hottest temperature measured in the state so far this year. Highs temperatures Tuesday and Wednesday in this region could reach 110° again, as the most extreme heat this week will stay focused over Oklahoma and surrounding states.

Jeff Masters

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Quoting wunderkidcayman:

nope it will be TD5


its moving W or just N or due West

between 65mph and 75mph

the intensity forecast now agree with me with bring it to Cat 2 hurricane in the W carib and TS within the next 24-36hours


Okay, but as it moves from ITCZ it should pull WNW, No?

Thx

Quoting islander101010:
waiting.for.nhc.intensity.forecast


Thx.

One of the big things is water and tides. The surf and rains can be so damaging. You can (to an extent) 'hide' from wind, cannot hide from water.
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Quoting bajelayman2:
The biggest thing is that the conditions are favourable for development, I would think that as there is nothing stopping it, we should be prepared for a few little surprises in development.
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If it is excessively humid and hot here in the next day or so, we will know that is bad news, that is typically the pre-storm weather, to a layman it seems like a coming storm is sucking everything up.
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Quoting bajelayman2:


Yup. Thx. Tomas gave a lot here in Barbados a wake up call. Barely a hurricane (at least on the border of storng storm and CAT 1), it caused some disruption for electicity for up to two weeks in some areas. A few had power back in a day or so, mine took four days, some two weeks.

For a '''ONLY Cat 1 or strong storm''' that took a lot of people by surprise, that it could be so damaging.
waiting.for.nhc.intensity.forecast
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Quoting caribbeantracker01:


nah use viz sat to look at the system not infrared but to me we may see tropical depression 2 or 3 form because all the past systems have went straight into storms

nope it will be TD5

Quoting bajelayman2:
Hi All,

Looks to me like its pulling away from ITCZ and moving WNW, starting to pull together too, at least from the satellite loop.

Last NHC track had it passing below BARBADOS, but from that development region, such as Ivan and Tomas, they usually pass very close to us here in Barbados.

It'll be close, just a question now of how strong.

its moving W or just N or due West

between 65mph and 75mph

the intensity forecast now agree with me with bring it to Cat 2 hurricane in the W carib and TS within the next 24-36hours
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Quoting islander101010:
hoping.for.live.updates.leeward.islanders...good. lu ck


Yup. Thx. Tomas gave a lot here in Barbados a wake up call. Barely a hurricane (at least on the border of storng storm and CAT 1), it caused some disruption for electicity for up to two weeks in some areas. A few had power back in a day or so, mine took four days, some two weeks.

For a '''ONLY Cat 1 or strong storm''' that took a lot of people by surprise, that it could be so damaging.
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The biggest thing is that the conditions are favourable for development, I would think that as there is nothing stopping it, we should be prepared for a few little surprises in development.
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1964. beell
nrt, if you're up and around, what happened to the 06Z NCEP/GFS run?
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hoping.for.live.updates.leeward.islanders...good.lu ck
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Cant see it going too far North, it'll pass thorugh the islands, just a quesiton of how high up.
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1961. SLU
Quoting SLU:
Looking at the latest microwave pass it does seem to be reforming near 11n 45w. Let's wait for confirmation at 12Z.


Also the latest model runs seem to initialise the system further north than last night.
Member Since: July 13, 2006 Posts: 13 Comments: 5364
1960. SLU
Looking at the latest microwave pass it does seem to be reforming near 11n 45w. Let's wait for confirmation at 12Z.
Member Since: July 13, 2006 Posts: 13 Comments: 5364
Quoting caribbeantracker01:


nah use viz sat to look at the system not infrared but to me we may see tropical depression 2 or 3 form because all the past systems have went straight into storms


I agree, Ivan and Tomas which both formed in that area, intensified really quickly.

As soon as this gets out of the ITCZ fully it'll ramp up.
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Hi All,

Looks to me like its pulling away from ITCZ and moving WNW, starting to pull together too, at least from the satellite loop.

Last NHC track had it passing below BARBADOS, but from that development region, such as Ivan and Tomas, they usually pass very close to us here in Barbados.

It'll be close, just a question now of how strong.
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Quoting bigwes6844:
oh really thats surprising
i.was.surprised.too
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Quoting SLU:
Is it me or has the center of 99L reformed further north?


nah use viz sat to look at the system not infrared but to me we may see tropical depression 2 or 3 form because all the past systems have went straight into storms
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Good morning. Very little change in 99L last night, just slowly getting itself together... Probably 50 or 60% at 8AM, maybe a TD tomorrow morning:



CMC still insisting on a northward track but at this point its a huge outlier as that is highly unlikely:



BTW I don't think I saw this posted on the blog last night; End of the 0z GFS run:



A bunch of ensemble members have shown this so its a real possibility... Almost certainly a fish storm if it develops as far east as the GFS shows.
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Quoting SLU:
Is it me or has the center of 99L reformed further north?
they.do.that
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Quoting SLU:
Is it me or has the center of 99L reformed further north?

nah it at 10.1N 45.8W moving W
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1952. SLU
Is it me or has the center of 99L reformed further north?
Member Since: July 13, 2006 Posts: 13 Comments: 5364
Quoting AussieStorm:


Cause he's a pest and takes enjoyment out of posting useless comments.


Good morning Aussie.It looks like the wave train is leaving the station.
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Quoting aspectre:
1913 ilovehurricanes13: weakening invest 99L UP 1012mb!
Nope, down to 1009millibars
1920 ilovehurricanes13: invest 99L IS MOVING WNW...NOW
99L has been headed between 273.7degreesWest and 278.3degreesWest for quite a while now.
Exactly WestNorthWest is 292.5degrees: so WNW describes a direction between 281.25degrees and 303.75degrees

1) Posting nonsense only gets you Ignored
2) CAPITALIZing or embolding everything within a comment just makes people skip reading that comment, and gets you Ignored.

So I gotta ask, why do you wanna to be ignored by others?



Cause he's a pest and takes enjoyment out of posting useless comments.


Hot towers in Saola.
Member Since: September 30, 2007 Posts: 9 Comments: 15962
6z SHIPS was run off of the NHC official track.

Seems that were getting close to classification.
Member Since: June 9, 2007 Posts: 4 Comments: 15947
Good morning everyone as I raise my coffee cup to you all.We definately need to keep our eye on this one(99L).As it could become a threat for someone on the Gulf Coast.Kit ready and prepared.
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as of now 99L is generally moving into lower shear via 0900utc shear maps
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1945. LargoFl
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1944. LargoFl
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1943. LargoFl
Quoting bigwes6844:
i was at work lurking on here and i saw these models leaning towards the GOM. that is a boiling pot ready to be served. Largo im in new orleans, i have two bags and a kit ready in case this thang becomes a huge monster!
..good for you, your ready, I am also, been ready for a month now, always do when the season looks to be active..so many..arent until the last moment
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Quoting islander101010:
below.normal.twc.just.reported
oh really thats surprising
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I geuss I was right with the strength of 99L the 06Z intensitiy forecast now saying strong cat 1 weak cat 2 in the caribbean
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Quoting LargoFl:
............IF this whatever it becomes makes it thru the Islands we all around the gulf coasts need to keep a very keen eye on this storm, I dont like some of the models paths that take this whatever it becomes..into the gulf of mexico.....this is a Very Good time...to prepare just in case...get those hurricane kits and plans ready...again...just in case
i was at work lurking on here and i saw these models leaning towards the GOM. that is a boiling pot ready to be served. Largo im in new orleans, i have two bags and a kit ready in case this thang becomes a huge monster!
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1939. LargoFl
..............by the looks of things..99L is still just a low pressure system with a 30 to 50% chance of development..it has NOT..developed yet..but needs to be watched closely i think
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1938. LargoFl
Quoting islander101010:
nothing.to.worry.about.this.week.thankfully...may be .next.wk.when.99.gets.closer
yes we do have time..now the islands have less time to prepare and i hope they are doing so because it sure looks like this IS going into their area on the latest model runs
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Quoting bigwes6844:
hopefully 99L doesnt get in the GOM because this storm could be on a way of become a bad storm. look at the water temps.
below.normal.twc.just.reported
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nothing.to.worry.about.this.week.thankfully...maybe .next.wk.when.99.gets.closer
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1935. LargoFl
............IF this whatever it becomes makes it thru the Islands we all around the gulf coasts need to keep a very keen eye on this storm, I dont like some of the models paths that take this whatever it becomes..into the gulf of mexico.....this is a Very Good time...to prepare just in case...get those hurricane kits and plans ready...again...just in case
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1934. LargoFl
.............Tampa Bay area 7-day
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1933. LargoFl
Quoting bigwes6844:
morning largo
..good morning
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Quoting LargoFl:
.................................Good morning everyone
morning largo
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1931. LargoFl
.................................Good morning everyone
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1930. LargoFl
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hopefully 99L doesnt get in the GOM because this storm could be on a way of become a bad storm. look at the water temps.
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Two typhoons at the same damn time!
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99L getting better organized cant wait to see if they go red on the percentage for 99L. IMO i say 60% or 70
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99L
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1925. gippgig
The latest issue of Science News (July 28; Vol. 182 No. 2) has an article "Calm, with an eye on the storm", p. 32) about a storm chaser who collects data about tornadoes.
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Damrey is now a typhoon.
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1913 ilovehurricanes13: weakening invest 99L UP 1012mb!
Nope, down to 1009millibars
1920 ilovehurricanes13: invest 99L IS MOVING WNW...NOW
99L has been headed between 273.7degreesWest and 278.3degreesWest for quite a while now.
Exactly WestNorthWest is 292.5degrees: so WNW generally describes a direction in the octant between 281.25degrees and 303.75degrees

1) Posting nonsense only gets you Ignored
2) CAPITALIZing or embolding everything within a comment just makes people skip reading that comment, and gets you Ignored.

So I gotta ask, why do you wanna to be ignored by others?

Member Since: Posts: Comments:

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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.

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