Atlantic ITCZ

[bvigal]

There was little SAL last year. Most of what was blamed on SAL was actually dry air / subsidence.

That's really interesting. When you say there was "little", do you mean over the entire Atlantic? Is there some place I can read about the recorded amount/position of SAL for various years?

OK, then do you think the actual dust: gritty, hazy, making people sneeze, etc. we had last year here in the Caribbean, persistant for days at a time from March through at least July, was from our nearby volcano, not Africa? We can usually tell the difference this way: Soufriere is greyish and not so gritty, Sahel dust is brown or red and very gritty when you wipe if off things. But, I'm totally open to learn more. If the meteorological community has scientific evidence that Saharan/Sahel dust wasn't really present last year, I want to read about it and educate myself.

[bvigal]

The more I look around, the more I find (NOAA, JPL, etc.) that there was considerable Saharan dust on July 20, 27 August 7, and Sept 21 of 2005. But I can't find the article that you mets have obviously read that says some conditions earlier identified as SAL were just dry air. Would you please point me in the right direction, so I can read it? Thanks.

[Aquawind]

http://www.aoml.noaa.gov/hrd/project2005/sal.html

Objectives:
Improve our understanding of the mechanisms by which the Saharan Air Layer’s (SAL’s) embedded mineral dust, low humidity, and low-level wind surge affect Atlantic tropical cyclone genesis and intensity change.

improve the representation of dry air in forecast models

investigate how the SAL interacts with the tropical cyclone inner core

improve our understanding of the SAL’s vertical structure

investigate the effect of mineral dust on cloud microphysics

improve the representation of vertical wind shear that is enhanced by the SAL surge

investigate the mechanisms that lead to strong SAL outbreaks over Africa

investigate the mechanisms by which the SAL maintains its thermodynamic structure

http://www.aoml.noaa.gov/hrd/Storm_page ... 807N1.html

http://www.aoml.noaa.gov/hrd/Storm_page ... 808N1.html

http://www.aoml.noaa.gov/hrd/Storm_page ... 927N1.html

http://www.aoml.noaa.gov/hrd/Storm_page ... 928N1.html


As senorpepr mentioned there was SAL but the in depth data collected was on only 4 flights. We are trying to learn more about SAL and it's interaction with tropical systems. I don't see any overview statement of the 2005 season here and unfortunately I cannot clarify it anymore than that. I would like to think if there was additional information someone would pass it on. As a person who is living in the British Virgin Islands like yourself you probably hear the word more than us USA mainlanders and are feeling the affects in more ways than one.

Additional links

http://www.aoml.noaa.gov/hrd/tcfaq/A17.html

http://www.gsfc.nasa.gov/feature/2004/0116dust.html

There were a number of papers presented at the recent 27th Conference on Hurricanes and Tropical Meteorology. I didn't see anything directly related to the SAL but I would think some of the presentations touched on the subject.


http://ams.confex.com/ams/27Hurricanes/ ... ed_339.htm


If you click on the wicked picture on the SAL Group page you can see additional links they provide. Email addresses are also available. I don't know how long the research is going to continue but I would hope more than just the 2005 season.

[bvigal]

Aquawind, thanks for posting those links!! While I've seen the salex project and the other aoml & gsfc links, I think many will find that info interesting.

I'm most anxious to read the papers from ams conference to look for clues why the mets think there was little or no sal, or rather that much of that mistaken for sal in 2005 was merely dry air.

Here's 2 more links which may not come across in google search, because rather old, but very interesting about dust and it's propensity to les. antilles, and effects.
http://soundwaves.usgs.gov/2002/03/
http://coastal.er.usgs.gov/african_dust/

Don't take my word for it, read what scientist Ginger Garrison writes - "Having lived in the Caribbean region for 18 years, I had spent the past decade documenting the continuing decline of coral reefs and was intimately aware of the influx of African dust every summer.... "

"Every year, hundreds of millions of tons of African dust are carried from the Sahara and Sahel across the Atlantic to the Caribbean and the southeastern United States. In the Caribbean, the sky becomes hazy, visibility decreases to a few kilometers, a fine red dust settles on surfaces, and residents complain of sinus problems, coughs, and other ailments said to be caused by the dust. Although the dust has been carried to the Caribbean for thousands of years, the amount transported varies from year to year and has increased drastically since the early 1970s with the beginning of the drought in the Sahel."

Of the years I've lived here, last summer being my 5th, it was no doubt the worst for dust. I don't mistake dry air for dust - dust is dirty, sky turns red, people can't breath. Dry air is clear and pure, not even remotely similar. That's why I'm so anxious to know what scientific evidence exists that there was 'little' sal last summer. I'm still just scratching my head

[cycloneye]

Very interesting all the above information that Paul (Aquawind) has posted here about the sal factor.Paul as you said the sal affects more the Eastern Caribbean islands than the U.S mainland.Also another minor factor that affects the NE Caribbean islands since 1995 are the many eruptions of the Souffiere volcano at Monserrat.Ash goes up and depending on the wind direction the ash affects the British and U.S Virgin Islands and Puerto Rico.It's unknown if this factor has any effect on the tropical waves or stronger systems that haved moved thru since 1995 over that volcano.

[caribepr]

All I know is that the coral reef damage we had/have throughout the Caribbean from last year (extending to now, those babies don't come back fast) was considered to be a result of Saharan dust and heat - in fact, said to be the worst in recorded history (the heat and the dust combo, with the results being the killing of coral which takes many many years to regenerate). There was even an article about it in the San Juan Star yesterday, how bad the coral kill still is.
So if it wasn't that...then was it just the temps of the water?? As bvigal said, we went through a lot of alerts to dust, people cautioned to be indoors who had any sort of breathing problems - and for a lot of us, eye irritation, coughing etc. worse than I've ever known it in the years I've lived in the Caribbean (over ten years now). I'm also curious to know if it really WASN'T Sahara dust...then what WAS it!!!??? (it's scary not knowing that - we know volcano and we know Sahara...but what don't we know?)

[bvigal]

Well, I'd be lying if I didn't wonder about last year and all our dust, and the absence of any organization of tropical activity! Have been wondering since about mid-August last year....

[senorpepr]

There was little SAL last year. Most of what was blamed on SAL was actually dry air / subsidence.

That's really interesting. When you say there was "little", do you mean over the entire Atlantic? Is there some place I can read about the recorded amount/position of SAL for various years?

OK, then do you think the actual dust: gritty, hazy, making people sneeze, etc. we had last year here in the Caribbean, persistant for days at a time from March through at least July, was from our nearby volcano, not Africa? We can usually tell the difference this way: Soufriere is greyish and not so gritty, Sahel dust is brown or red and very gritty when you wipe if off things. But, I'm totally open to learn more. If the meteorological community has scientific evidence that Saharan/Sahel dust wasn't really present last year, I want to read about it and educate myself.

When I said "little SAL" I meant it in both ways... in terms of coverage and total amount. From what I remembered and studied... the amount of transported sand was less than normal, but that doesn't mean that SAL was devoid.

The point I was trying to hammer in (although lately my brain has been "hammering" with a headache ) was that most of the things blamed on SAL last year was actually dry air and/or subsidence.

I'm not trying to say you didn't see any Saharan dust... I know parts of the Caribbean had some nasty battles with the dust. What I'm saying is people tend to fly the SAL flag whenever they feel freaky enough.

The root cause of the frequent SAL flag flying, in my opinion, is associated with inexperienced people looking at water vapor imagery. While I'm glad to see WV imagery utilized, people tend to go only use the enhanced NOAA WV data. Once again, don't get me wrong, the NOAA site is great. However, the enhancement that site uses tends to mislead inexperienced folks.

Drier air -- air with less water vapor -- is enhanced to show up in the color brown. People tend to associate the color brown with dust. In a majority of the SAL flag flying episode for yesteryear, the real culprit was dry air and/or subsidence and not dusty air via Africa.

[CHRISTY]

Guys this is the first time i see an area by africa shaded in purple!

[Ivan14]

Wow so tropical development is possible near Africa provided there is a wave?

[HurricaneHunter914]

http://www.ssd.noaa.gov/PS/TROP/DATA/RT/EATL/IR4/20.jpg

The ITCZ is making its way up north now. Looks like there is a little spin to it too.

[CHRISTY]

on the image i posted above shows the first time purple comes out near the capeverde region. you can also see some spin to this wave on this IR loop. maybe this is probably were we will see our first invest!

http://www.orbit.nesdis.noaa.gov/smcd/opdb/aviation/loops/realtime/tropicsir_loope.html

[HurricaneHunter914]

Don't you mean third?

[CHRISTY]

yea my bad!

[NONAME]

Actully it would be the first invest the first on was in south atlantic and L. is actully for the north atlantic and the 90L for that i dont think counts and the second one was actully a test 91L so technecly it would be are first invest.

[CHRISTY]

Actully it would be the first invest the first on was in south atlantic and L. is actully for the north atlantic and the 90L for that i dont think counts and the second one was actully a test 91L so technecly it would be are first invest.

yea thats what i had thought!thanks for clearing that up.

[CHRISTY]

WHEN THE ITCZ MOVES A LITTLE FUTHER NORTH....WE WILL BE IN ACTION RATHER QUICKLY.CHECK OUT ALL THE CONVECTION OVER AFRICA AND ITS ONLY MAY.... :eek:

[Scorpion]

Wow, pretty active.

[Aquawind]

Well the ITCZ has some dramatic differences in comparison to the mean. The ITCZ continues to be pushed southward as is exits the African coast. Overall it is considered north of the mean..although I think it is still below the mean location over the Atlantic waters.


http://www.cpc.ncep.noaa.gov/products/f ... itcz.shtml

During the period from May 11-20, 2006, the African portion of the Intertropical Convergence Zone was located near 13.5 degrees north latitude when averaged from 15W-35E over the ten day period. This compares to the normal location of 13.3N, and a position during the previous dekad of 12.8N. While the current position averaged over the entire region is near normal, examining figure 1 will show that there are significant differences in the western and eastern zones. To the west of Nigeria, areas are experiencing a slight southward bias of the ITCZ position when comparing it to the climatological mean, and to the east of Nigeria, areas are seeing a more northward bias of the ITCZ position. The current position corresponds to the accumulated dekadal rainfall well, especially in the east where the ITCZ seems to have taken a slight jump to the north (Seen in figure 1). Examining figure 3 which depicts the ITCZ vs normal for the area of 20-35 degrees east, it is seen that after beginning the season well south of normal, the ITCZ has rapidly moved northward and is now located north of the long term mean normal for the dekad. Additional information may be found at: http://www.cpc.ncep.noaa.gov/products/f ... itcz.shtml

[AussieMark]

to compare to 2006 position at this time last year

Period May 11-20

15°W
2006: 10.2°N
2005: 13.4°N

10°W
2006: 12.3°N
2005: 14.2°N

5°W
2006: 13.7°N
2005: 15.0°N

0°
2006: 14.7°N
2005: 15.0°N

5°E
2006: 14.6°N
2005: 13.2°N

10°E
2006: 14.0°N
2005: 11.3°N

15°E
2006: 13.9°N
2005: 11.1°N

20°E
2006: 13.4°N
2005: 11.9°N

25°E
2006: 12.7°N
2005: 9.9°N

30°E
2006: 13.8°N
2005: 10.3°N

35°E
2006: 16.2°N
2005: 12.4°N