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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2021. WxLogic
I would keep 99L at 50% until it clears 50W. If it's successful at completely detaching from the ITCZ, sustaining convection, and fighting some shear around 50W then I would bump it up to 70%.
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Quoting SLU:


It will most likely pass south of PR but the models has shifted a bit north this morning so PR could get some more weather from it if this happens.


Yes,that 00z Euro was very interesting as it shifted north and tracks it closer to PR.
Member Since: April 29, 2009 Posts: 75 Comments: 13992
Quoting bajelayman2:


Near Wildey.
ok im in Ch Ch
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Good Morning , Is the center of 99L around 11N/47W?
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Quoting StormTracker2K:


CMC and the Euro are right on top of each other in send a storm to FL. It looks as if FL may a 3rd storm to region so far this hurricane season. Storm could be here in 7 to 8 days.

CMC and to a degree the Euro say a TS or hurricane hits the east coast of FL in 8 days.


the CMC is the outlier
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bajelayman 2 is this weekend crop over festival?
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Quoting SLU:
The TWO should be lifted to code RED this morning by all means.


should be posted within 10-15 mins from now

Quoting islander101010:
major.hurricane.maybe

possibly the intensity forecast is now agreeing with me on it becoming a Cat 2 hurricane
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Quoting MAweatherboy1:
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.


CMC and the Euro are right on top of each other in send a storm to FL. It looks as if FL may a 3rd storm to region so far this hurricane season. Storm could be here in 7 to 8 days.

CMC and to a degree the Euro say a TS or hurricane hits the east coast of FL in 8 days.

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2012. WxLogic
Good Morning
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Quoting RidingTheStormOut:
Good Morning Friends, Back for the season, amateur noob that I be, I only come on during season. Thanks in advance everyone, for all the neat info I osmose during the season. Lots of folks with lots of cool info. Amateur point of view.... The Caribbean will be the graveyard for 99L.
gilbert.wasnt..lowest.barometer.reading.ever.reco rded.se.domincan.republic
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Quoting barbados246:
You are very correct and its sad to say this but when we really do have a serious disaster thatis when we are going to start paying more attention.where on the island are you?


Near Wildey.
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Quoting caribbeantracker01:
it would be td 3 if not someone tell me if all the systems were topical depressions when they formed?


no it will not it will be TD5
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Quoting wunderkidcayman:


just to tell you W can have N movements too pluss steering shows W till it enter the caribbean then a W-WNW track thereafter that shoud take it to Jamaica and the Cayman Islands
major.hurricane.downstream
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Quoting RidingTheStormOut:
Good Morning Friends, Back for the season, amateur noob that I be, I only come on during season. Thanks in advance everyone, for all the neat info I osmose during the season. Lots of folks with lots of cool info. Amateur point of view.... The Caribbean will be the graveyard for 99L.

the caribbean is not the graveyard
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2006. SLU
The TWO should be lifted to code RED this morning by all means.
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Quoting stoormfury:
As if the threat of pre ernesto is not enough both GFS and the ECMWF has another strong disturbance heading for the island chain in 9 days time frame


Well, this is the time for it...starting August things usually do ramp up around middle/ end August. Bit early though, Ivan was end of August.

We may have a bit of an active season.

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Quoting HurricaneHunterJoe:


Twas the Guru
I also predicted it would be a TD today by 4:45pm (from a survey)...am I an idiot too? LOL
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Quoting stoormfury:
WV can give an indication of a centre if the system is vertically stacked. i know the micro wave pass is an indicator and no way i was saying that wv loops are used to pinpoint ant centre

ok cause you made it soud that way
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Good Morning Friends, Back for the season, amateur noob that I be, I only come on during season. Thanks in advance everyone, for all the neat info I osmose during the season. Lots of folks with lots of cool info. Amateur point of view.... The Caribbean will be the graveyard for 99L.
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2000. SLU
Quoting luigi18:

Do you think she will be close to us here in the Puerto Rico area??


It will most likely pass south of PR but the models has shifted a bit north this morning so PR could get some more weather from it if this happens.
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1999. MoeWest
Quoting wunderkidcayman:


yes it shows upper levels


keep on dreaming and wishing

Quoting wunderkidcayman:


yes it shows upper levels


keep on dreaming and wishing



Im using reverse psychology on this system.
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TUTT is ruling right now
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1997. ryang
Morning all

I see 99L is looking better this morning. Lets see what the TWO says.
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1996. SLU
Quoting stoormfury:
morning
SLU you are very correct there has been a reformation of the centre. if you were to look at the water vapour of the system ,using RAMSDIS java WV loop and the centre is at 11n 46w moving north of west .at a little faster clip


yep .. it's further north this morning looking at the visible imagery and the low level could lines.
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WV can give an indication of a centre if the system is vertically stacked. i know the micro wave pass is an indicator and no way i was saying that wv loops are used to pinpoint ant centre
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1994. SLU
Quoting stoormfury:
the system is nearing TD status and i would not be surprise if it is desinated TD5 later today. i expect the system to get stroger as it approaches the 55 deg long mark, where sss is warmer. reminds me of the position of TOMAS IN 2110.


I don't think there's enough atmospheric instability for it to rapidly intensity in that region like Tomas did when it strengthened from the minimal TS to a cat. 2 hurricane in less than 24 - 36 hours.
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Quoting stoormfury:
the system is nearing TD status and i would not be surprise if it is desinated TD5 later today. i expect the system to get stroger as it approaches the 55 deg long mark, where sss is warmer. reminds me of the position of TOMAS IN 2110.
Back to the future...LOL Good Morning! Agree that even with my untrained eye, it looks to be organizing.
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Quoting bajelayman2:


You are right, but at least a lot more seem to be aware and cautious. I guess it will take time.

A friend of mine from Antigua, explained how they come to be so prepared, after their terrible hurricane experiences of the 80's and 90's.

Lets hope it does not take that to make us prepared.

Honestly, my biggest worry (not discounting wind, obviously), is water damage on the Coast, I really think we have a major problem if a CAT 2 or CAT 3 passes. The island has a lot to lose on the coastlines and having seen what water has done elsewhere, it has to be a worry.

That, and the hurricane she;ter system needs revamping, from what I see, a lot more could be done and planned, I agree with you fully on that, the disaster plan does not seem to be well thought out, just my opinion.
You are very correct and its sad to say this but when we really do have a serious disaster thatis when we are going to start paying more attention.where on the island are you?
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Quoting weatherh98:


Doesnt water vapor show upper levels


yes it shows upper levels

Quoting MoeWest:
Ok. Lets see what the Curacao shield does now. I think 99L will suddenly disappear into nothingness about a couple of hours before reaching our islands.

keep on dreaming and wishing

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I'm out by
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Quoting stoormfury:
the system is nearing TD status and i would not be surprise if it is desinated TD5 later today. i expect the system to get stroger as it approaches the 55 deg long mark, where sss is warmer. reminds me of the position of TOMAS IN 2110.

I agree on the first half
and you ment SST not SSS
and I did not know that the NHC does nameing out at 2110 lol j/k I know that is a typo
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As if the threat of pre ernesto is not enough both GFS and the ECMWF has another strong disturbance heading for the island chain in 9 days time frame
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1986. MoeWest
Ok. Lets see what the Curacao shield does now. I think 99L will suddenly disappear into nothingness about a couple of hours before reaching our islands.
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1985. luigi18
Quoting SLU:
Looking at the latest microwave pass it does seem to be reforming near 11n 45w. Let's wait for confirmation at 12Z.

Do you think she will be close to us here in the Puerto Rico area??
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Quoting wunderkidcayman:

dude you don't use WV to find low level center of circulations


Doesnt water vapor show upper levels
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Quoting bajelayman2:
Hi Barbados246.
hey and good morning to you. Nice to meet you
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Quoting stoormfury:
the system is nearing TD status and i would not be surprise if it is desinated TD5 later today. i expect the system to get stroger as it approaches the 55 deg long mark, where sss is warmer. reminds me of the position of TOMAS IN 2110.


Do you have the windsat, I'm on my phone and can't see it. That would be useful right now
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Quoting barbados246:
bajei find since Alot of us here are still never prepared and still not taking this system seriously;


You are right, but at least a lot more seem to be aware and cautious. I guess it will take time.

A friend of mine from Antigua, explained how they come to be so prepared, after their terrible hurricane experiences of the 80's and 90's.

Lets hope it does not take that to make us prepared.

Honestly, my biggest worry (not discounting wind, obviously), is water damage on the Coast, I really think we have a major problem if a CAT 2 or CAT 3 passes. The island has a lot to lose on the coastlines and having seen what water has done elsewhere, it has to be a worry.

That, and the hurricane she;ter system needs revamping, from what I see, a lot more could be done and planned, I agree with you fully on that, the disaster plan does not seem to be well thought out, just my opinion.
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Quoting stoormfury:
morning
SLU you are very correct there has been a reformation of the centre. if you were to look at the water vapour of the system ,using RAMSDIS java WV loop and the centre is at 11n 46w moving north of west .at a little faster clip

dude you don't use WV to find low level center of circulations
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the system is nearing TD status and i would not be surprise if it is desinated TD5 later today. i expect the system to get stroger as it approaches the 55 deg long mark, where sss is warmer. reminds me of the position of TOMAS IN 2110.
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Quoting caribbeantracker01:
the system seems to be following the gfs scenario the one on the weather channel tropical update

how surprising, the gfs is right at the moment..... AGAIN
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morning
SLU you are very correct there has been a reformation of the centre. if you were to look at the water vapour of the system ,using RAMSDIS java WV loop and the centre is at 11n 46w moving north of west .at a little faster clip
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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 am out for a week, I pop in to say hi and I see 99L and then those ensembles... -___- seriously?

Anyway. Can't stay on long have to get ready for 6:30 and be out of the hotel by 7:00 don't know when I can come back but I will try.
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Quoting bajelayman2:


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

Thx



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.


just to tell you W can have N movements too pluss steering shows W till it enter the caribbean then a W-WNW track thereafter that shoud take it to Jamaica and the Cayman Islands
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baje
Quoting barbados246:
Action: Quote | Modify Comment
Member Since: May 20, 2010 Posts: 0 Comments: 63
i find since
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.
Alot of us here are still never prepared and still not taking this system seriously;
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the system seems to be following the gfs scenario the one on the weather channel tropical update

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Hi Barbados246.
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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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Jeff co-founded the Weather Underground in 1995 while working on his Ph.D. He flew with the NOAA Hurricane Hunters from 1986-1990.