Two African waves worth mentioning

By: Dr. Jeff Masters , 3:51 PM GMT on July 18, 2009

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There are two African tropical waves worth mentioning today, though neither looks particularly threatening. A tropical wave near 12N 45W, about 1200 miles east of the Lesser Antilles Islands (97 L), is moving west at 15 - 20 mph. This wave is now surrounded by an area of very dry air from the Sahara Desert. The dry air has disrupted most of the wave's heavy thunderstorm activity, and will continue to make it difficult for this system to develop over the next 2 - 3 days. Wind shear is a modest 10 knots over the disturbance, and should remain in the moderate 10 - 15 knot range over the next 2 - 3 days. Thereafter, shear is expected to rise to 20 - 30 knots. This morning's QuikSCAT pass showed no evidence of a surface circulation, and only a modest wind shift associated with 97L. The National Hurricane Center is giving this system a low (less than 30% chance) of developing into a tropical depression in the next 48 hours.

A second tropical wave now approaching the northern Lesser Antilles Islands is under 30 knots of wind shear, and has little prospect of development due to the high shear. However, the wave will bring heavy rain to the islands over the next two days.

None of the computer models are forecasting tropical storm development over the next seven days, and I don't expect either of the two African waves mentioned today to develop over at least the next three days.


Figure 1. Current satellite image of African wave 97L, 1200 miles east of the Lesser Antilles Islands.

I'll have an update Sunday afternoon.
Jeff Masters

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Morning bloggers and bloggettes.

So from what I gather ex 97L is making a come back?
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It is now heading to 29c waters
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1748. IKE
Quoting Weather456:
Here's the tropical weather outlook for Felix a day b4 it was updgraded to TD 6
210
ABNT20 KNHC 291513
TWOAT
TROPICAL WEATHER OUTLOOK
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
1130 AM EDT WED AUG 29 2007

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

A TROPICAL WAVE LOCATED ABOUT 900 MILES EAST OF THE WINDWARD ISLANDS
IS PRODUCING SHOWERS AND THUNDERSTORMS. ALTHOUGH THIS ACTIVITY IS
CURRENTLY DISORGANIZED...ENVIRONMENTAL CONDITIONS ARE EXPECTED TO
GRADUALLY BECOME MORE FAVORABLE FOR DEVELOPMENT AS THE SYSTEM MOVES
WESTWARD AT 15 TO 20 MPH.


That sounds more encouraging then what their saying for 97L.

I understand your point though.
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Quoting IKE:
I was surprised they deactivated 97L.

Then again, how do you go from 94L to 97L?


lol the whole hurricane season is messed up.

90L? Ana?
Medium probability for 93L
and where the heck was 95L and 96L.
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1746. DDR
Quoting stormwatcherCI:
Cayman uses de-sal and reverse osmosis. Only one reservoir on the whole island of Grand Cayman and a lot of people still use cisterns.

Cisterns are common here as well,mostly found in rural areas where water supply is irregular.
No big suprise here,we're 3rd world but developing somewhat.
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1744. msphar
Time and persistence. Yesterday it was a ghost. Today, it is back somewhat. Looks like the Windwards will get the brunt of this thing in 40 hours or so.
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1743. IKE
I was surprised they deactivated 97L.

Then again, how do you go from 94L to 97L?
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Here's the tropical weather outlook for Felix a day b4 it was updgraded to TD 6
210
ABNT20 KNHC 291513
TWOAT
TROPICAL WEATHER OUTLOOK
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
1130 AM EDT WED AUG 29 2007

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

A TROPICAL WAVE LOCATED ABOUT 900 MILES EAST OF THE WINDWARD ISLANDS
IS PRODUCING SHOWERS AND THUNDERSTORMS. ALTHOUGH THIS ACTIVITY IS
CURRENTLY DISORGANIZED...ENVIRONMENTAL CONDITIONS ARE EXPECTED TO
GRADUALLY BECOME MORE FAVORABLE FOR DEVELOPMENT AS THE SYSTEM MOVES
WESTWARD AT 15 TO 20 MPH.
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1741. IKE
Quoting stormwatcherCI:
Ok, I know it doesn't look disorganized to me either but what do I know. I am just going by the "experts."


I hear ya.

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Good morning all. I'm new on here, but can anybody tell me if shear has lessened over the eastern carib. as expected
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Quoting IKE:


I don't see that as remaining disorganized. I understand the NHC being conservative, but....sometimes their a little too conservative.
Ok, I know it doesn't look disorganized to me either but what do I know. I am just going by the "experts."
Member Since: October 9, 2008 Posts: 0 Comments: 8399
Quoting centex:
I think they are somewhat lost when no model support.


very true, i was thinking the same thing. I believe their outlooks incoporate global model guidance so I would not entirely be upset with them.
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Quoting Weather456:


We have aquifers (reservoirs), the Caribbean should approach desalination since we have an abundance of water. Only Aruba i know have desalination plants.
Cayman uses de-sal and reverse osmosis. Only one reservoir on the whole island of Grand Cayman and a lot of people still use cisterns.
Member Since: October 9, 2008 Posts: 0 Comments: 8399
1735. IKE
Quoting stormwatcherCI:
Maybe remain disorganized but getting better organized ?


I don't see that as remaining disorganized. I understand the NHC being conservative, but....sometimes their a little too conservative.
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Quoting futuremet:


Notice how the blob's circulation (what circulation! lol) is more elongated, and how the wave is of it is more compact.


yep and also on 850 mb vort, satellite imagery and low level derived winds.
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Quoting IKE:


Agree.

That has a yellow circle? I would have dropped it.

Their the experts, but some of their actions are puzzling.


Anyone can make mistakes, it is not their fault. However it would be discreet if they did not remain obstinate.
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1732. centex
I think they are somewhat lost when no model support.
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Quoting DDR:

I hope you get some today,i see scattered showers in the northern islands on radar.
Do you have a reservoir or do you Desalinate on your island?


We have aquifers (reservoirs), the Caribbean should approach desalination since we have an abundance of water. Only Aruba i know have desalination plants.
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1730. IKE
Quoting Weather456:
The only thing disorganize is this



Agree.

That has a yellow circle? I would have dropped it.

Their the experts, but some of their actions are puzzling.
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Quoting IKE:
REMAINS DISORGANIZED

WTH? I must be blind.
Maybe remain disorganized but getting better organized ?
Member Since: October 9, 2008 Posts: 0 Comments: 8399
Quoting Weather456:
Circulation



Notice how the blob's circulation (what circulation! lol) is more elongated, and how the wave is of it is more compact.
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The only thing disorganize is this

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1726. IKE
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1725. DDR
Quoting Weather456:


Yea we did not get much, less than 1/2 an inch, much of the showers we had was short and pasing.

I hope you get some today,i see scattered showers in the northern islands on radar.
Do you have a reservoir or do you Desalinate on your island?
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1724. SLU
Disorganised but improving gradually. It looks good on the microwave imagery this morning. I still expect the invest to be reactivated at 12z.
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1723. WxLogic
Quoting Weather456:
Notice something in the 8am TWO to the 2am TWO.

2 am they said upper winds were unfavorable, now they are saying development if any will be slow to occur.

97L is giving the NHC a run for their money.


I believe at 2AM they were skeptic about the upper flow, but seems they're gaining more confidence about how the upper flow is starting to shape up since then.
Member Since: August 14, 2008 Posts: 4 Comments: 4978
Circulation

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Quoting Weather456:
Notice something in the 8am TWO to the 2am TWO.

2 am they said upper winds were unfavorable, now they are saying development if any will be slow to occur.

97L is giving the NHC a run for their money.


LOL Yes, I was disappointed when they switched their attention to that diffluent-induced-blob yesterday.
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1720. IKE
Quoting stormdude77:


Me too


SAL is almost gone around it.
It's under 5-10 knots of shear.
SST's are 28-29C.
It has low-level convergence.
It has upper-level divergence.
It has a good 850 mb vorticity.

What am I missing for it to get going?
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1719. WxLogic
Quoting IKE:
TROPICAL WEATHER OUTLOOK
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
800 AM EDT SUN JUL 19 2009

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

SHOWERS AND THUNDERSTORMS HAVE DIMINISHED IN ASSOCIATION WITH A
TROPICAL WAVE LOCATED OVER THE EASTERN CARIBBEAN SEA. UPPER-LEVEL
WINDS ARE UNFAVORABLE FOR SIGNIFICANT DEVELOPMENT OF THE SYSTEM AS
IT MOVES WEST-NORTHWESTWARD AT AROUND 15 MPH. THERE IS A LOW
CHANCE...LESS THAN 30 PERCENT...OF THIS SYSTEM BECOMING A TROPICAL
CYCLONE DURING THE NEXT 48 HOURS.

SHOWER AND THUNDERSTORM ACTIVITY REMAINS DISORGANIZED IN ASSOCIATION
WITH A TROPICAL WAVE LOCATED ABOUT 700 MILES EAST OF THE WINDWARD
ISLANDS. DEVELOPMENT OF THIS SYSTEM...IF ANY...WILL BE SLOW TO
OCCUR AS IT MOVES WESTWARD AT 15 TO 20 MPH. THERE IS A LOW
CHANCE...LESS THAN 30 PERCENT...OF THIS SYSTEM BECOMING A TROPICAL
CYCLONE DURING THE NEXT 48 HOURS.

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

$$
FORECASTER BRENNAN


That's what I though... although I was hoping the yellow "circle" was going to get dropped for the wave in the E CARIB. as I don't see anything happening with that one in the near future.
Member Since: August 14, 2008 Posts: 4 Comments: 4978
Notice something in the 8am TWO to the 2am TWO.

2 am they said upper winds were unfavorable, now they are saying development if any will be slow to occur.

97L is giving the NHC a run for their money.
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Quoting IKE:
REMAINS DISORGANIZED

WTH? I must be blind.


Me too
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1716. IKE
REMAINS DISORGANIZED

WTH? I must be blind.
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It'll be interesting to see if Ex 97L can hold convection during the day. If it can, I think it has a very good chance of developing....
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1714. IKE
TROPICAL WEATHER OUTLOOK
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
800 AM EDT SUN JUL 19 2009

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

SHOWERS AND THUNDERSTORMS HAVE DIMINISHED IN ASSOCIATION WITH A
TROPICAL WAVE LOCATED OVER THE EASTERN CARIBBEAN SEA. UPPER-LEVEL
WINDS ARE UNFAVORABLE FOR SIGNIFICANT DEVELOPMENT OF THE SYSTEM AS
IT MOVES WEST-NORTHWESTWARD AT AROUND 15 MPH. THERE IS A LOW
CHANCE...LESS THAN 30 PERCENT...OF THIS SYSTEM BECOMING A TROPICAL
CYCLONE DURING THE NEXT 48 HOURS.

SHOWER AND THUNDERSTORM ACTIVITY REMAINS DISORGANIZED IN ASSOCIATION
WITH A TROPICAL WAVE LOCATED ABOUT 700 MILES EAST OF THE WINDWARD
ISLANDS. DEVELOPMENT OF THIS SYSTEM...IF ANY...WILL BE SLOW TO
OCCUR AS IT MOVES WESTWARD AT 15 TO 20 MPH. THERE IS A LOW
CHANCE...LESS THAN 30 PERCENT...OF THIS SYSTEM BECOMING A TROPICAL
CYCLONE DURING THE NEXT 48 HOURS.

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

$$
FORECASTER BRENNAN
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Quoting DDR:

Hey!
I'm from Trinidad,hope you'r good?

456
How much rain did you get yesterday?
It looked as if the most of the rain was south/se of you.


Yea we did not get much, less than 1/2 an inch, much of the showers we had was short and pasing.
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.
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1710. DDR
Quoting stormwatcherCI:
I think I asked you before but I don't remember which island you are on so can you please remind me.

Hey!
I'm from Trinidad,hope you'r good?

456
How much rain did you get yesterday?
It looked as if the most of the rain was south/se of you.
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Quoting Weather456:
DDR in T&T
Thanks. I couldn't remember what he said. Right in line for whatever comes of 97L.
Member Since: October 9, 2008 Posts: 0 Comments: 8399
Quoting stormwatcherCI:
I think I asked you before but I don't remember which island you are on so can you please remind me.


He's in Trinidad
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DDR in T&T
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1706. IKE
Quoting Weather456:
What wall of shear? The Antilles wave never stood a chance where it was. Different systems, different upper level patterns.


Exactly. Just look at the CIMSS shear map.

The wave that just entered the Caribbean is history. Just look at a visible loop.

Former 97L has promise.
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Quoting DDR:
Morning all,
My fellow Caribbean people,you all want rain,now here it comes,we've had our share over the past 2 weeks.
I think I asked you before but I don't remember which island you are on so can you please remind me.
Member Since: October 9, 2008 Posts: 0 Comments: 8399
What wall of shear? The Antilles wave never stood a chance where it was. Different systems, different upper level patterns.
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1703. WxLogic
Based on 1701. Post above... looks like they're keeping both areas with <30%... and still giving the Carib wave some chance as it's under an upper level high.
Member Since: August 14, 2008 Posts: 4 Comments: 4978
Quoting WPBHurricane05:
1000 PM HST SAT JUL 18 2009

FOR THE CENTRAL NORTH PACIFIC...BETWEEN 140W AND 180

1. A cluster of thunderstorms located 500 to 700 miles south of the Big Island of Hawaii has shown signs of increased organization over the past 12 hours. Some additional development of this system is possible over the next 48 hours as it moves west at 20 to 25 mph.


Thats CP91, declared early this morning

CP 91 2009071906 BEST 0 98N 1557W 25 1009 DB
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TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
805 AM EDT SUN JUL 19 2009

...TROPICAL WAVES...
AN ATLANTIC OCEAN TROPICAL WAVE WAS RE-POSITIONED SLIGHTLY
TO 37W TO THE SOUTH OF 16N MOVING WESTWARD 10 TO 15 KT.
IT WAS MOVED BASED ON THE SATELLITE IMAGERY. NO NEARBY
PRECIPITATION.

AN ATLANTIC OCEAN TROPICAL WAVE IS ALONG 48W TO THE SOUTH OF 16N
MOVING WEST 15 TO 20 KT. BROAD UPPER LEVEL CYCLONIC FLOW COVERS
THE ATLANTIC OCEAN FROM 7N TO 14N BETWEEN 45W AND 54W. STRONG
SHOWERS AND THUNDERSTORMS ARE FROM 10N TO 13N BETWEEN 49W AND
52W. MODERATE SHOWERS ARE ELSEWHERE FROM 10N TO 13N BETWEEN
44W AND 56W.

A CARIBBEAN SEA TROPICAL WAVE IS ALONG 65W TO THE SOUTH OF 22N
MOVING WESTWARD 15 TO 20 KT. THE WAVE IS MOVING AWAY FROM THE
UPPER LEVEL TROUGH THAT WAS RIGHT ON TOP OF IT 24 HOURS AGO. THE
WAVE NOW IS MOVING THROUGH AN AREA OF UPPER LEVEL ANTICYCLONIC
WIND FLOW THAT COVERS THE CARIBBEAN SEA TO THE SOUTH OF 20N TO
THE EAST OF A LINE FROM SOUTHEASTERN CUBA TO THE NORTH CENTRAL
HONDURAS COAST. ISOLATED MODERATE SHOWERS ARE FROM 13N TO 18N
BETWEEN 64W AND 70W...AND FROM 22N TO 23N BETWEEN 64W AND 65W.
Member Since: September 10, 2007 Posts: 0 Comments: 11323
1700. WxLogic
Quoting weathermanwannabe:
Unless I am missing something; are you guys giving 97L a chance "above" the current NHC 30%?............While 97L looks good, I see it heading towards the same wall of sheer that tore apart the Antilles system in the overnight hours....Am I way off?.............Thanks


Hehe.. at least I'm still with NHC on this one with a <30% chance.
Member Since: August 14, 2008 Posts: 4 Comments: 4978

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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.