New tropical depression could form off the coast of Africa

By: Dr. Jeff Masters , 1:12 PM GMT on September 25, 2009

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A tropical wave (99L) is located near 15N, 30W, about 300 miles west of the Cape Verdes Islands. This wave has seen an increase in heavy thunderstorm activity this morning, and low-level spiral bands have formed. The system can already be classified as a tropical depression using the satellite-based Dvorak technique. This morning's QuickSCAT pass showed a loose but closed circulation, with top winds of 30 mph in the heaviest thunderstorms. Wind shear is moderate, about 10 - 20 knots. There is a modest amount of dry air to 99L's west that does not appear to be interfering with the storm's organization.


Figure 1. Morning visible satellite image of Invest 99L (left side of image) and a new tropical wave moving off the coast of Africa.

As 99L moves west-northwest over the next two days, sea surface temperatures will cool by 1°C and winds shear will remain in the moderate range. Some dry air may also affect the storm. These conditions give 99L a good chance of forming into a tropical depression, and NHC has given the system a moderate (30 - 50%) chance of developing into a tropical depression by Sunday. By Monday, wind shear will increase to the high range, 20 - 30 knots, and 99L will probably weaken or be torn apart. None of the computer models forecast development of 99L or any other system in the Atlantic over the next seven days.

A new tropical wave with plenty of heavy thunderstorm activity and some spin is moving off the coast of Africa today. This wave is under a moderate amount of wind shear, 10 - 20 knots, and has some potential for development this week as it moves west or west-northwest past the Cape Verdes Islands.

The latest wind shear forecasts from our major computer models show high values of wind shear affecting most of the tropical Atlantic for the next ten days. This is typical for an El Niño year, and it will be difficult for any storms to get to hurricane strength over the next ten days because of the high shear. The latest 16-day GFS forecast predicts wind shear will decline some by the 2nd week of October, though.


Figure 2. Wind shear forecast for Thursday, October 2 at 00 UTC made by last night's 00Z run of the GFS model. Wind shear is expected to be high over most of the tropical Atlantic for the next ten days, including the Caribbean. Wind shear values below 8 m/s (about 15 knots, red colors), are typically needed to support tropical storm formation.

Jeff Masters

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They never cease to crack me up Dan. Good for the blog. Keeps people smiling (and apparently ban-proof).
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That's what lightning rods do is dissipate (hopefully) that build up. A lot of people think they attract lightning – and sometimes they do – but they’re designed to do the opposite.
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Quoting mikatnight:
#212...
How in the world does he do it???


and
Member Since: August 22, 2008 Posts: 12 Comments: 6010
215. JRRP
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Quoting PcolaDan:




Just this last summer I was at Disney with friends over from England. Car was at Animal Kingdom, which closes earlier than the other parks. We had gone over to Epcot. As we were walking to the car, one of about three in the lot, I saw lightning in the distance. Four adults and three kids. Suddenly I noticed the hair on the little girl start standing up. Snapped my head around to look towards my wife and sure enough, so was hers. The Brit friends didn't know what was going on, but noticed the hair and thought it looked cool. I said no, that means lightning may be trying to build right here, RUN TO THE CAR!!!!


Ive seen that before and the strike was 20 feet away. It hit a pin tree, besides that we were the tallest thing for a couple of hundred feet around.
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#212...
How in the world does he do it???
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Quoting atmoaggie:

Looks like the correct statement is the lightning capitol of the US or the lightning death capital of the world. Thanks to Dan.




Just this last summer I was at Disney with friends over from England. Car was at Animal Kingdom, which closes earlier than the other parks. We had gone over to Epcot. As we were walking to the car, one of about three in the lot, I saw lightning in the distance. Four adults and three kids. Suddenly I noticed the hair on the little girl start standing up. Snapped my head around to look towards my wife and sure enough, so was hers. The Brit friends didn't know what was going on, but noticed the hair and thought it looked cool. I said no, that means lightning may be trying to build right here, RUN TO THE CAR!!!!

Member Since: August 22, 2008 Posts: 12 Comments: 6010
TD 8 Loop
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Aggie -
and I ask you this with the utmost respect - what exactly do you believe as far as GW is concerned (I apologize for not knowing, as I%u2019m sure you%u2019ve answered that question somewhere before that I missed).
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209. JRRP
Quoting BurnedAfterPosting:


wait wait, we cant have TD 8 can we?

I thought the season was over? It is december 1st right? No more storms for September right? No more storms for 2009 right?

LMAO

jeje
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This is not the same situation as Fred for those wondering. Fred was in higher temps and lower amount of dry air around it.
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Quoting tornadofan:


You called it man! Way to go!

(just kidding...)


wait wait, we cant have TD 8 can we?

I thought the season was over? It is december 1st right? No more storms for September right? No more storms for 2009 right?

LMAO
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206. Murko
Quoting Santamaria:
What is important to see in these graphs is that there was a natural cooling cycle as we go into another glacial period over the last 2000 years (we've been in an interglacial period), but that this has been superceded by warming in the last 200 years or so,

That warming is man-made and is very rapid in millenium terms.

These graphs confirm the original "hockey stick" scenario,


That's right. In the '70s they were concerned with global cooling and finding ways to combat it, as we should have been due to start entering the next glacial period. The next ice age has been put off 15,000 to 50,000 years. We should be in a cooling period now, so doesn't that just add strength to the argument that we're causing the warming?
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KEEPER.This is usually where I sign off and don't look at this site for days.It usually takes about 2 hours after Dr. Masters post when he says nothing is in the Atlantic for all of the wishers to say there is a Cat 5 heading this way. Good thing I keep my senses
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Quoting KEEPEROFTHEGATE:
well its 3 o'clock now schools out they will be on any moment now wishcasting the hell out of 08l

lol

get ready
Yes, We will be hearing the name GRACE alot.
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Quoting Santamaria:
@atmoaggie. Here's more recent paper (Sept 2008) on Kilimanjiro that you might find interesting. It's a pdf so it takes time to load,

http://www.bioone.org/doi/pdf/10.1659/mrd.981?cookieSet=1

Its conclusion; at the present rate of ice loss the mountain will be completely clear of ice in 2010.

Possible to see from satellite images how the surrounding land is getting drier and losing vegetation cover too. It's not only Australia that's turning into a dustbowl.

This is good AGW discussion.

Cannot get that link to load for some reason.

There has been work on how the deforestation around Kilimanjaro has lowered the water vapor in the area, which leads to less or no snowfall.

"According to Nature’s Betsy Mason, “Although it’s tempting to blame the (Kilimanjaro) ice loss on global warming, researchers think that deforestation of the mountain’s foothills is the more likely culprit.”

Forests at the base of Kilimanjaro have been steadily disappearing for decades. “Without the forests’ humidity,” Mason reports, “previously moisture-laden winds blew dry. No longer replenished with water, the ice is evaporating in the strong equatorial sunshine.”"

What measurements we have show no warming at all anywhere near Kilimanjaro. The only AGW going on there is in the mainstream media (hopefully we as a society will stop with CNN "science" specials).

"According to Hardy, forest reduction in the areas surrounding Kilimanjaro, and not global warming, might be the strongest human influence on glacial recession. "Clearing for agriculture and forest fires—often caused by honey collectors trying to smoke bees out of their hives—have greatly reduced the surrounding forests," he says. The loss of foliage causes less moisture to be pumped into the atmosphere, leading to reduced cloud cover and precipitation and increased solar radiation and glacial evaporation.

Evidence of glacial recession on Kilimanjaro is often dated from 1912, but most scientists believe tropical glaciers began receding as early as the 1850s. Stefan L. Hastenrath, a professor of atmospheric studies at the University of Wisconsin, Madison, has found clues in local reports of a dramatic drop in East African lake levels after 1880. Lake evaporation indicates a decrease in precipitation and cloudiness around Kilimanjaro. "
http://news.nationalgeographic.com/news/2003/09/0923_030923_kilimanjaroglaciers.html
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well its 3 o'clock now schools out they will be on any moment now wishcasting the hell out of 08l

lol

get ready
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201. JRRP
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Quoting tornadodude:
Pretty much confused me there 456, you quoted yourself, and then told yourself that you called it? LOL


I think its brilliant myself
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Quoting tornadofan:
Well, looks like September may squeeze out another named storm. Another weak, wimpy named storm, which is fine by me.


You called it man! Way to go!

(just kidding...)
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may be grace in a few hrs as darkness falls and dmax approaches
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197. JRRP
Quoting Weather456:


well you called it

136. Weather456 6:13 PM GMT on September 25, 2009
a depression is forming in the Eastern Atlantic. We may have Grace in a couple of days


remember 456 the season is OVER... lol
xD.... :P
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mikatnight.I'm sure you were very close to me
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"We may have Grace in a couple of days"

Everybody say Grace (but not in a religious way)...
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Pretty much confused me there 456, you quoted yourself, and then told yourself that you called it? LOL
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LOL
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Quoting PalmBeachWeather:
Yes, south Florida is the lightening capital. I have been in Palm Beach county for 26 years. Every year many people have been struck by lightening. To be honest I really do not blame it on the frequency of lightening strikes , but I do blame it on all of us parrotheads sitting out under the tiki huts thinking we will be safe while drinking margarita's


You're over on the island right? Just came from there a little while ago - had to do some electrical work. I'm just on the other side of the Lantana bridge...
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BBL
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so your patting yourself on the back? LOL!!!
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Quoting ElConando:
In about 30 mins we will know if nhc will issue and early advisory or wait till 5.


Most likely wait till 5.
Quoting Weather456:


well you called it

136. Weather456 6:13 PM GMT on September 25, 2009
a depression is forming in the Eastern Atlantic. We may have Grace in a couple of days



yea
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In about 30 mins we will know if nhc will issue and early advisory or wait till 5.
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Quoting Santamaria:
@atmoaggie. Here's more recent paper (Sept 2008) on Kilimanjiro that you might find interesting. It's a pdf so it takes time to load,

http://www.bioone.org/doi/pdf/10.1659/mrd.981?cookieSet=1

Its conclusion; at the present rate of ice loss the mountain will be completely clear of ice in 2010.

Possible to see from satellite images how the surrounding land is getting drier and losing vegetation cover too. It's not only Australia that's turning into a dustbowl.

This is good AGW discussion.


I agree! You folks have been great...
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Quoting Weather456:
Tropical depression 8 has form

invest_RENUMBER_al992009_al082009.ren


well you called it

136. Weather456 6:13 PM GMT on September 25, 2009
a depression is forming in the Eastern Atlantic. We may have Grace in a couple of days

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Yes, south Florida is the lightening capital. I have been in Palm Beach county for 26 years. Every year many people have been struck by lightening. To be honest I really do not blame it on the frequency of lightening strikes , but I do blame it on all of us parrotheads sitting out under the tiki huts thinking we will be safe while drinking margarita's
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Dan (#177) You nailed it! Thanks again.
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Quoting mikatnight:


Re: "True" Is that based on actual strikes, or the number of people struck, I wonder?

Looks like the correct statement is the lightning capitol of the US or the lightning death capital of the world. Thanks to Dan.
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Tropical depression 8 has form

invest_RENUMBER_al992009_al082009.ren
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TROPICAL CYCLONE EIGHT (AL082009) 20090925 1800 UTC
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@atmoaggie. Here's more recent paper (Sept 2008) on Kilimanjaro that you might find interesting. It's a pdf so it takes time to load,

http://www.bioone.org/doi/pdf/10.1659/mrd.981?cookieSet=1

Its conclusion; at the present rate of ice loss the mountain will be completely clear of ice in 2010.

Possible to see from satellite images how the surrounding land is getting drier and losing vegetation cover too. It's not only Australia that's turning into a dustbowl.

This is good AGW discussion.
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WE HAVE 08L
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Quoting PalmBeachWeather:
tornadodude....Yes, I do have add, That's my problem I guess, And I do have Dyslexia, 5 out or 4 people have it.


well, I've also heard that some places are 50% below sea level
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Quoting mikatnight:
Thanks Dan. Checking it out now...


Edited comment and added this.
From The Observer News.
Florida leads the nation in deaths caused by lightning. The reasons for that are straightforward %u2013 Florida has both a high population and typically a large amount of lightning. In Hillsborough County, 32 people were killed by lightning between 1959 and 2003 %u2013 a number matched only by Miami-Dade County.

Only South and Central America, tropical Africa and Asia tend to have more lightning than Florida. Rwanda in Africa is generally considered to be the lightning capital of the world. But that is a fine distinction as Florida %u2013 and more specifically Hillsborough County %u2013 is thought to be the lightning capital of the U.S.
Member Since: August 22, 2008 Posts: 12 Comments: 6010
CHGHUR

TROPICAL CYCLONE GUIDANCE MESSAGE

NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL

1843 UTC FRI SEP 25 2009



DISCLAIMER...NUMERICAL MODELS ARE SUBJECT TO LARGE ERRORS.

PLEASE REFER TO NHC OFFICIAL FORECASTS FOR TROPICAL CYCLONE

AND SUBTROPICAL CYCLONE INFORMATION.



ATLANTIC OBJECTIVE AIDS FOR



TROPICAL CYCLONE EIGHT (AL082009) 20090925 1800 UTC



...00 HRS... ...12 HRS... ...24 HRS. .. ...36 HRS...

090925 1800 090926 0600 090926 1800 090927 0600



LAT LON LAT LON LAT LON LAT LON

BAMS 16.1N 31.1W 18.5N 33.9W 21.1N 35.6W 23.0N 36.1W

BAMD 16.1N 31.1W 17.5N 33.2W 19.2N 34.9W 20.6N 35.9W

BAMM 16.1N 31.1W 17.7N 33.4W 19.4N 35.3W 20.9N 36.3W

LBAR 16.1N 31.1W 17.5N 32.8W 19.3N 34.2W 21.0N 35.0W

SHIP 30KTS 37KTS 40KTS 40KTS

DSHP 30KTS 37KTS 40KTS 40KTS



...48 HRS... ...72 HRS... ...96 HRS. .. ..120 HRS...

090927 1800 090928 1800 090929 1800 090930 1800



LAT LON LAT LON LAT LON LAT LON

BAMS 24.6N 36.2W 26.8N 34.5W 24.6N 30.5W 22.6N 25.6W

BAMD 21.9N 36.4W 23.3N 37.3W 23.4N 37.8W 21.8N 37.5W

BAMM 22.0N 37.0W 23.6N 38.2W 23.8N 38.7W 21.9N 38.8W

LBAR 22.3N 34.9W 23.7N 33.1W 23.9N 28.6W 25.8N 19.4W

SHIP 41KTS 42KTS 43KTS 41KTS

DSHP 41KTS 42KTS 43KTS 41KTS



...INITIAL CONDITIONS...

LATCUR = 16.1N LONCUR = 31.1W DIRCUR = 305DEG SPDCUR = 12KT

LATM12 = 14.8N LONM12 = 29.0W DIRM12 = 300DEG SPDM12 = 11KT

LATM24 = 13.8N LONM24 = 26.9W

WNDCUR = 30KT RMAXWD = 20NM WNDM12 = 20KT

CENPRS = 1008MB OUTPRS = 1012MB OUTRAD = 125NM SDEPTH = M

RD34NE = 0NM RD34SE = 0NM RD34SW = 0NM RD34NW = 0NM



$$

NNNN
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With the continous parade of troughs across the atlantic,don't see anything coming off Africa having much of a future
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tornadodude....Yes, I do have add, That's my problem I guess, And I do have Dyslexia, 5 out or 4 people have it.
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Thanks Dan. Checking it out now...
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Quoting PalmBeachWeather:
Weather456.I do not post very often, but I listen intently with what you have to say


your welcome. and thanks
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Quoting atmoaggie:

I thought so, but could immediately find the SAL description.

So without a sounding, any way to figure which levels are the driest ahead of 99?


yea, you can use soundings and the upper air time cross sections available on TAFB but both are the same obs and both are confined to land areas.

There are two ways you find out:

1) by taking numerical models and looking at the RH at each level starting at 1000 mb to 200 mb the region 99L is located in.

2) since low to mid water vapor is the one forecasters look at to determine TC cyclogenesis, you can still use TPW loops to get an average of the RH from the surface to the the mid-levels since that part normally carries the greater percentage of vapor pressure. For example if the air is dry on TPW, it is likely that this dry air lies between 800 mb and 500 mb, becuz that is where the greatest vapor pressure is. some may lie in the upper levels but becuz the density is not much, that proportion of dry air is smaller.
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Quoting atmoaggie:

True.
Pondering the dynamics about that mountain...would have to be an upslope flow...


Re: "True" Is that based on actual strikes, or the number of people struck, I wonder?
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Quoting hydrus:
lol


its catchy haha
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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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