Dust forecast for the 2009 Atlantic hurricane season

By: Dr. Jeff Masters , 6:58 PM GMT on June 20, 2009

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There will be less African dust than usual over the tropical Atlantic during this year's hurricane season, according to a new experimental dust forecast issued by Dr. Amato Evan of the University of Wisconsin. Dr. Evan used a statistical model that correlated levels of dust activity in past years with rainfall over the Sahel region of Africa and a natural regional wind pattern known as the North Atlantic Oscillation (NAO). He forecasts that dust levels over the Main Development Region (MDR, 8 - 20°N & 15 - 65°W) for Atlantic hurricanes during this year's hurricane season will be similar to last year's below-average levels, thanks in large part to plentiful rains over the Sahel region of Africa during the 2008 rainy season (Figure 1). However, the dust levels expected this year do not approach the record lows seen in 1994 and 2005. Dust forecasts made in May or June are skillful going out five months, with a skill 11 - 16% better than a "no-skill" forecast using climatology.


Figure 1. Rainfall over the Sahel region of Africa was generally 50 - 100 mm (2 - 4 inches) above average during the 2008 rainy season (about 20 - 80% above average). The heavy rains promoted vigorous vegetation growth in 2009, resulting in less bare ground capable of generating dust. Image credit: NOAA/Climate Prediction Center.

The Sahara and the Sahel: significant sources of dust
The summertime dust that affects Atlantic tropical storms originates over the southwestern Sahara (18° - 22° N) and the northwestern Sahel (15° - 18° N) (Figure 2). The dust that originates in the Southwest Sahara stays relatively constant from year to year. However, the dust from the northwestern Sahel varies significantly from year to year, and understanding this variation may be a key factor in improving our forecasts of seasonal hurricane activity in the Atlantic. The amount of dust that gets transported over the Atlantic depends on a mix of three main factors: the large scale and local scale weather patterns (windy weather transports more dust), how wet the current rainy season is (wet weather will wash out dust before it gets transported over the Atlantic), and how dry and drought-damaged the soil is. The level of drought experienced in the northwestern Sahel during the previous year's rainy season (June - October) is the key factor of the three in determining how much dust gets transported over the Atlantic during hurricane season, according to a January 2004 study published in Geophysical Research Letters published by C. Moulin and I. Chiapello. A dry rainy season the previous year will make an expanded area of loose soil which can create dust. It is also possible that the corresponding changes in vegetation can alter the regional weather patterns, causing more dust production.


Figure 2. Map of the mean summer dust optical thickness derived from satellite measurements between 1979 and 2000. Maximum dust amounts originate in the northern Sahel (15° to 18° N) and the Sahara (18° to 22° N). The Bodele depression in Chad is also an active dust source. Image credit: Evidence of the control of summer atmospheric transport of African dust over the Atlantic by Sahel sources from TOMS satellites (1979-2000) by C. Moulin and I. Chiapello, published in January 2004 in Geophysical Research Letters.

How dust suppresses hurricanes
Dust acts as a shield which keeps sunlight from reaching the surface. Thus, large amounts of dust can keep the sea surface temperatures up to 1°C cooler than average in the hurricane Main Development Region (MDR) off the coast of Africa, providing hurricanes with less energy to form and grow. Dust also affects the Saharan Air Layer (SAL), an layer of dry, dusty Saharan air that rides up over the low-level moist air over the tropical Atlantic. At the boundary between the SAL and low-level moist air where the trade winds blow is the trade wind inversion--a region of the atmosphere where the temperature increases with height. Since atmospheric temperature normally decreases with height, this "inversion" acts to but the brakes on any thunderstorms that try to punch through it. This happens because the air in a thunderstorm's updraft suddenly encounters a region where the updraft air is cooler and less buoyant than the surrounding air, and thus will not be able to keep moving upward. The dust in the SAL absorbs solar radiation, which heats the air in the trade wind inversion. This makes the inversion stronger, which inhibits the thunderstorms that power a hurricane. The dust may also act to interfere with the formation of cloud drops and rain drops that these thunderstorms need to grow, but little is known about such effects. It is possible that dust may act to help hurricanes by serving as "condensation nuclei"--centers around which raindrops can form and grow.

For additional reading
Dr. Evan published a study in Science magazine this March showing that 69% of the increase in Atlantic sea surface temperatures over the past 26 years could be attributed to decreases in the amount of dust in the atmosphere.

Jeff Masters

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844. IKE
Quoting KEEPEROFTHEGATE:
thats a go my friend and you shall be replaced with empty space just like whats in your head


LOL!
Member Since: June 9, 2005 Posts: 23 Comments: 37860
Quoting IKE:
However...if the center moves any farther to the northeast...Andres
could weaken significantly more than forecast in a couple of days.


Good...keep moving NE and go inland and die.



if it keeps moving great slows down and dumps heavy rain no good!
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Quoting G35Wayne:
Wow this really is gonna be a slow season. June is almost over and there hasnt been one named storm yet. Usaully we get one by this time you goofs..
thats a go my friend and you shall be replaced with empty space just like whats in your head
Member Since: July 15, 2006 Posts: 178 Comments: 56059
Quoting CybrTeddy:
BOC Blob, shear is marginal. Climotology favored area.


Does anyone have a map showing the low-level steering currents? (the currents used for 980mb+ storms) Just trying to get an idea what kind of environment the BOC blob will be moving into, based on current steering.
Member Since: August 3, 2008 Posts: 16 Comments: 5891
838. Skyepony 3:18 PM GMT

I'm not complaining........it beats staring down one of those Cape Verde monsters.

Maybe later.

BoynSea
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surf-weather report b/4 I head out - check out the Gulf Temp.!
If dreams of tubes danced in your head last night, that's all they were when you woke up...dreams. There is a small 1' wave breaking right on shore this morning. The huge high tide making it hard for much improvement early, but the wind will blow all day and should increase the surf towards afternoon even though the tide will be making it's way back out. Kiters heads up plenty of wind the next few days and with that out going tide later could make for a good sesh this afternoon. Tomorrow looks like a better chance at something rideable with a chance of rain early on. Gulf Temp 89

Today...Northwest winds around 15 knots. Surf 1-2' . moderate chop.
Tonight...West winds around 15 knots. surf builds 1-3'. light chop. Isolated thunderstorms.
Tuesday...West winds around 15 knots. Surf 2-3'. moderate chop. Isolated thunderstorms.
Tuesday Night...West winds around 10 knots. Surf 2'. light chop. Isolated thunderstorms.
Wednesday...Northwest winds around 10 knots. Surf 1-2'. light chop. Isolated thunderstorms in the morning...then scattered thunderstorms in the afternoon.
Wednesday Night...West winds around 10 knots becoming south in the late evening and overnight. Surf 1-3'. Scattered thunderstorms in the evening...then isolated thunderstorms after midnight.
Thursday...Southwest winds around 10 knots. Surf 1-3'.. Isolated thunderstorms in the morning... Then scattered thunderstorms in the afternoon.
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838. Skyepony (Mod)
Boynsea~ Not suprised. Atleast a few nasty, fast moving blobs otta pop up around there the next few.

BOC is certainly looking gamely.
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Quoting extreme236:


Actually, on average only one named storm forms in June every two years.


and guess what we had one in june last year,so this year it would be par to the course if we did not have one!!!
Member Since: October 5, 2007 Posts: 20 Comments: 4970
29C waters combined with somewhat favorable wind shear in the BOC could give us an invest to track at least.
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Member Since: July 8, 2005 Posts: 259 Comments: 24574
829. Skyepony 3:03 PM GMT

Yes, maybe so. We just had a little surprise disturbance pass thru here (Abaco, Bahamas). Up to 40 mph winds, with rain behind it. Thought I'd have to tie down the dogs for a minute, there. Clearing now.

BoynSea
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BOC Blob, shear is marginal. Climotology favored area.
Member Since: July 8, 2005 Posts: 259 Comments: 24574
Quoting G35Wayne:
Wow this really is gonna be a slow season. June is almost over and there hasnt been one named storm yet. Usaully we get one by this time you goofs..


2008 didn't have a named storm in June, Arthur just crossed into June from May. 2004 didn't see a named storm till July 31st, 2002 didn't see its first till Mid-July. PLUS we've already had a system, TD-1 in May.
Member Since: July 8, 2005 Posts: 259 Comments: 24574
829. Skyepony (Mod)
Oh & my windows were covered in condensation this morning. The 'cane breeding waters off the East coast of FL are offically open..
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828. Skyepony (Mod)
This weeks ENSO numbers are out. As promised the march into El Niño continues.

Region 1,2 +.9
Region 3 +.8
region 3,4 +.7
Region 4 +.6

Quickly passed the +.5 threshold across the Pacific.

Looking at the T-depth annomily, can really see this one evolve. Not only has the ocean recharged its quickly gathering more heat in the depths. The top of this is the top of the water, the bottom is the bottom of the ocean, right side S America & it moves left (west) across the Pacific. The top 1/3rd with the heat will lift to the surface from right to left as El Niño evolves.

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Quoting IKE:
However...if the center moves any farther to the northeast...Andres
could weaken significantly more than forecast in a couple of days.


Good...keep moving NE and go inland and die.



No No, go out to sea and not hurt anyone.
Member Since: July 8, 2005 Posts: 259 Comments: 24574
826. IKE
However...if the center moves any farther to the northeast...Andres
could weaken significantly more than forecast in a couple of days.


Good...keep moving NE and go inland and die.

Member Since: June 9, 2005 Posts: 23 Comments: 37860
Quoting hurricane2009:


It was a UFB

Unidentified Festering Blob lol


Somehow, I think that the term "UFB" will stick around here for a while now. I like it.
Member Since: August 3, 2008 Posts: 16 Comments: 5891
Hey gang...hope all you dads had a great day yesterday.

Any thoughts on the 00z NGP showing a system froming in the Carribean then heading into the gulf?

Link

(if this has already been discussed, I'll look back at previous posts)
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Quoting G35Wayne:
Wow this really is gonna be a slow season. June is almost over and there hasnt been one named storm yet. Usaully we get one by this time you goofs..


Actually, on average only one named storm forms in June every two years.
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Wow this really is gonna be a slow season. June is almost over and there hasnt been one named storm yet. Usaully we get one by this time you goofs..
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820. HadesGodWyvern (Mod)
Japan Meteorological Agency
Tropical Disturbance Summary
21:00 PM JST June 22 2009
===========================================

At 12:00 PM UTC, Tropical Depression, Former Linfa (1000 hPa) located at 28.0N 121.0E has 10 minute sustained winds of 25 knots with gusts of 40 knots. The depression is reported as moving northeast at 10 knots.
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WPAC system- Link

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817. HadesGodWyvern (Mod)
Japan Meteorological Agency
Tropical Disturbance Summary
21:00 PM JST June 22 2009
===========================================

Subject: Tropical Depression In Sea East Of The Philippines

At 12:00 PM UTC, Tropical Depression (1002 hPa) located at 10.6N 129.2E has 10 minute sustained winds of 30 knots with gusts of 45 knots. The depression is reported as moving west at 10 knots.
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816. HadesGodWyvern (Mod)
Joint Typhoon Warning Center

Tropical Cyclone Formation Alert (1000z 22JUN)
============================================
An area of convection (92W) located at 10.6N 131.1E or 285 NM northwest of Palau. Animated multispectral satellite imagery depicts cyclonic flow around a consolidating low level circulation center northwest of Palau moving generally west-northwest. A partial TRMM pass shows convective banding wrapping into an organized low level circulation center. Upper level analysis shows low vertical wind shear over the system with a developing upper level cyclonic circulation center to the east, just west of Guam. The upper level circulation is providing a developing outflow channel for the system.

Maximum sustained winds near the center is 15-20 knots with a minimum sea level pressure of 1007 MB. Since the low level circulation is becoming more organized, the potential for this disturbance to form into a significant tropical cyclone within the next 24 hours is UPGRADED TO GOOD.
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...SUMMARY OF 800 AM PDT INFORMATION...
LOCATION...16.0N 102.0W
MAXIMUM SUSTAINED WINDS...50 MPH
PRESENT MOVEMENT...NORTH-NORTHWEST OR 330 DEGREES AT 5 MPH
MINIMUM CENTRAL PRESSURE...997 MB
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the difference in the amount of radiation entering the earths atmosphere and leaving is the reason for weather!!!!!
Member Since: October 5, 2007 Posts: 20 Comments: 4970
TROPICAL STORM ANDRES FORECAST/ADVISORY NUMBER 4
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL EP022009
1500 UTC MON JUN 22 2009

AT 800 AM PDT...1500 UTC...THE GOVERNMENT OF MEXICO HAS ISSUED A
TROPICAL STORM WARNING FOR THE SOUTHWESTERN COAST OF MEXICO FROM
LAZARO CARDENAS TO MANZANILLO. A TROPICAL STORM WARNING MEANS THAT
TROPICAL STORM CONDITIONS ARE EXPECTED SOMEWHERE WITHIN THE WARNING
AREA WITHIN 24 HOURS.

AT 800 AM...THE GOVERNMENT OF MEXICO HAS ISSUED A HURRICANE WATCH
FOR THE SOUTHWESTERN COAST OF MEXICO FROM LAZARO CARDENAS TO CABO
CORRIENTES. A HURRICANE WATCH MEANS THAT HURRICANE CONDITIONS ARE
POSSIBLE WITHIN THE WATCH AREA...GENERALLY WITHIN 36 HOURS.

AT 800 AM...THE TROPICAL STORM WATCH FOR THE COAST OF MEXICO FROM
LAZARO CARDENAS TO ZIHUATANEJO HAS BEEN DISCONTINUED.
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Some feisty wind barbs in there.
Member Since: September 22, 2005 Posts: 18 Comments: 2343
Shear is very unfavorable for the Bahamas thing to form, but shear looks marginal for the BOC blob to form.. I think the blob looks good because it's under low wind shear.
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Quoting hurricane2009:


It was a UFB

Unidentified Festering Blob lol


lol thats a good way to put it
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Quoting extreme236:


I don't think it is a moisture surge from Andres, but rather an area of convection that was hovering east of Andres yesterday...not sure what it was.


Whatever it is, it's not going to have enough time to become a TD or a Storm, possibly an Invest but knowing the NHC this year, NADA!
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Just got back from a 3 day field exercise to go play Army and god was it hot. Heat Category 5 the entire weekend. It was so sweltering that in the afternoon we had mandatory downtime because it was too hot to conduct any operations. I have never sweat so much in my life before. Really gives me a newfound respect for those in Iraq during the summer with the heat they have to deal with on a daily basis. Body Armor alone adds 10 degrees to the heat index.



We were easily in the black for 18 of the 24 hours of each day. Talk about embracing the suck for 3 days.
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TROPICAL CYCLONE GUIDANCE MESSAGE

1250 UTC MON JUN 22 2009


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

PLEASE REFER TO NHC OFFICIAL FORECASTS FOR TROPICAL CYCLONE

AND SUBTROPICAL CYCLONE INFORMATION.

EAST PACIFIC OBJECTIVE AIDS FOR


TROPICAL CYCLONE ANDRES (EP022009) 20090622 1200 UTC



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

090622 1200 090623 0000 090623 1200 090624 0000



LAT LON LAT LON LAT LON LAT LON

BAMS 15.8N 101.9W 17.1N 102.3W 18.3N 103.0W 19.5N 104.1W

BAMD 15.8N 101.9W 16.8N 102.9W 17.9N 104.2W 19.0N 105.5W

BAMM 15.8N 101.9W 17.0N 102.9W 18.2N 104.2W 19.5N 105.7W

LBAR 15.8N 101.9W 16.9N 102.6W 18.4N 103.7W 20.2N 105.0W

SHIP 45KTS 50KTS 55KTS 55KTS

DSHP 45KTS 50KTS 55KTS 55KTS



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

090624 1200 090625 1200 090626 1200 090627 1200



LAT LON LAT LON LAT LON LAT LON

BAMS 20.4N 105.2W 21.6N 108.1W 22.8N 111.8W 23.7N 115.9W

BAMD 19.8N 107.1W 21.2N 110.7W 22.3N 114.6W 23.5N 118.5W

BAMM 20.5N 107.3W 21.5N 111.5W 22.3N 115.9W 22.7N 120.7W

LBAR 21.7N 106.3W 24.0N 108.8W 25.8N 110.6W 27.4N 111.0W

SHIP 55KTS 50KTS 39KTS 27KTS

DSHP 55KTS 50KTS 39KTS 27KTS



...INITIAL CONDITIONS...

LATCUR = 15.8N LONCUR = 101.9W DIRCUR = 330DEG SPDCUR = 4KT

LATM12 = 15.0N LONM12 = 101.5W DIRM12 = 325DEG SPDM12 = 4KT

LATM24 = 14.6N LONM24 = 100.5W

WNDCUR = 45KT RMAXWD = 40NM WNDM12 = 35KT

CENPRS = 997MB OUTPRS = 1004MB OUTRAD = 120NM SDEPTH = M

RD34NE = 30NM RD34SE = 60NM RD34SW = 30NM RD34NW = 30NM
Member Since: July 15, 2006 Posts: 178 Comments: 56059
Quoting reedzone:
I'm looking at the BOC "blob" even though it might be a moisture surge from TS Andres, I think it might have a possibility of just becoming Invest 93L before it makes landfall.


I don't think it is a moisture surge from Andres, but rather an area of convection that was hovering east of Andres yesterday...not sure what it was.
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079

NOUS42 KNHC 221400

WEATHER RECONNAISSANCE FLIGHTS

CARCAH, NATIONAL HURRICANE CENTER, MIAMI, FL.

1000 AM EDT MON 22 JUNE 2009

SUBJECT: TROPICAL CYCLONE PLAN OF THE DAY (TCPOD)

VALID 23/1100Z TO 24/1100Z JUNE 2009

TCPOD NUMBER.....09-025



I. ATLANTIC REQUIREMENTS

1. NEGATIVE RECONNAISSANCE REQUIREMENTS.

2. OUTLOOK FOR SUCCEEDING DAY.....NEGATIVE.



II. PACIFIC REQUIREMENTS

1. TROPICAL STORM ANDRES

FLIGHT ONE -- TEAL 70

A. 23/1800Z

B. AFXXX 0102E ANDRES

C. 23/1300Z

D. 18.4N 104.0W

E. 23/1700Z TO 23/2100Z

F. SFC TO 10,000 FT



2. SUCCEEDING DAY OUTLOOK.....NEGATIVE.

JWP
Member Since: July 15, 2006 Posts: 178 Comments: 56059
I'm looking at the BOC "blob" even though it might be a moisture surge from TS Andres, I think it might have a possibility of just becoming Invest 93L before it makes landfall.
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801. IKE
12Z NAM at 42 hours...relief for the Florida panhandle...



Member Since: June 9, 2005 Posts: 23 Comments: 37860
800. IKE
Quoting ALCoastGambler:
Ike lost computer yesterday and was unable to thank you for your response. Thank you!!
Be careful this weekend with the heat. We are under severe heat adv. for our area. I wish I could . I have to be next to a smoker for the church all day


Thanks....good luck staying cool. I see a break coming this week. It gets better, hopefully, every day this week:)
Member Since: June 9, 2005 Posts: 23 Comments: 37860
Ike lost computer yesterday and was unable to thank you for your response. Thank you!!
Be careful this weekend with the heat. We are under severe heat adv. for our area. I wish I could . I have to be next to a smoker for the church all day
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Looks like something might want to get going in the BOC
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jeffy:no need to appologize,I was laughing at your comment;)....it looks like the mjo pulse is definately doing its thing,it should be active for the next 7-10 days in east pac and maybe even the GOM/west carib!!!!!
Member Since: October 5, 2007 Posts: 20 Comments: 4970


HUMIDEX 85.2F
Member Since: July 15, 2006 Posts: 178 Comments: 56059
794. IKE
Quoting gulfcoastdweller:


yes!! we need to do a rain dance


Oh....kay....crank it up


Where did ya get the gun John?
Member Since: June 9, 2005 Posts: 23 Comments: 37860

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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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