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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Quoting ilovehurricanes13:
its getting better looking now..

Sure is.


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Quoting StormTracker2K:


That should be 40% and the wave behind it should be at 20%. NHC definitely isn't quick to pull the trigger on these waves this year.
My humble take on this. They are just playing safe to avoid "errors"; the waves still very far from land no problem with doing that.
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Quoting stormchaser19:


which path you choose ?
a) GFS
b) ECMWF
c) NOGAPS
d) CMC
e) MY PATH

I choose e) LOL


C)
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Member Since: August 6, 2011 Posts: 4 Comments: 37064
Quoting robert88:
Caribbean bound to it's death. The W Atlantic is just not ready to sustain a a significant storm at this time...but it's getting there. The lid comes in a couple of weeks when the MJO returns and conditions could be more favorable at that time. 99L needs to detach from the ITCZ if it's going to even develop.


Why will it die in the Caribbean?
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IF it takes the southerly track and survives beyond the 120hr. and hits that bathtub water look out.
Quoting Patrap:
12z Early Cycle NHC model tracks
Invest99
Statistical/Simple Models (CLIPER,BAMs,LBAR,other Statistical Models)



Dynamic Models (More sophisticated models)




Early Model Wind Forecasts


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Stormchaser- Your path, ECMWF & GFS is bringing 99L right into my front garden, so I'm going with the CMC...
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Caribbean bound to it's death. The W Atlantic is just not ready to sustain a a significant storm at this time...but it's getting there. The lid comes in a couple of weeks when the MJO returns and conditions could be more favorable at that time. 99L needs to detach from the ITCZ if it's going to even develop.
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Quoting SFLWeatherman:
Q. What day will we have a TD or TS
A. TD today
B. TS today
C. TD tomorrow
D. TS tomorrow


Still in 20%
I think NHC will wait maybe 3 advisories to declare DEPRESION

c)TD tomorrow and maybe d)
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211. etxwx
A UN team is to visit flood-hit parts of North Korea to assess damage, after dozens of people died in recent storms.
BBC 31 July 2012
Excerpt: A rapid assessment team would visit the two worst-hit counties to see what help could be provided, a UN official said. North Korea announced on Saturday that flooding had killed 88 people between 18-25 July and left more than 60,000 homeless. State media said on Sunday that more heavy rain was expected, with many rivers and dams expected to flood.

Images from Anju city showed houses submerged under flooding
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12z Early Cycle NHC model tracks
Invest99
Statistical/Simple Models (CLIPER,BAMs,LBAR,other Statistical Models)



Dynamic Models (More sophisticated models)




Early Model Wind Forecasts

Member Since: Posts: Comments:


Member Since: September 30, 2007 Posts: 9 Comments: 15932
20 years ago this year, the baddest storm to hit SFLA in my lifetime, Andrew,

sent us into a surreal sense of impending doom here in south florida. It will be

interesting to me how the anniversary goes-AUG.24th.
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.................panama city florida
Member Since: August 6, 2011 Posts: 4 Comments: 37064
Quoting stormchaser19:


which path you choose ?
a) GFS
b) ECMWF
c) NOGAPS
d) CMC
e) MY PATH

I choose e) LOL


The one of least resistance.
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Quoting AussieStorm:
..surely one amazing storm, the size of the whole state of alabama..geez
Member Since: August 6, 2011 Posts: 4 Comments: 37064
Quoting stormchaser19:


which path you choose ?
a) GFS
b) ECMWF
c) NOGAPS
d) CMC
e) MY PATH

I choose e) LOL


AEMN
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which path you choose ?
a) GFS
b) ECMWF
c) NOGAPS
d) CMC
e) MY PATH

I choose e) LOL
Member Since: Posts: Comments:
Member Since: August 6, 2011 Posts: 4 Comments: 37064
Louisiana Landfalls:
Name Saffir-Simpson
Category Date of closest approach Year Name Saffir-Simpson
Category Date of closest approach Year
Unnamed 2 August 25 1852 Unnamed 1 October 16 1923
Unnamed 3 September 16 1855 Unnamed 3 August 26 1926
Unnamed 4 August 11 1856 Unnamed 3 June 16 1934
Unnamed 3 August 11 1860 Unnamed 1 August 15 1938
Unnamed 2 September 15 1860 Unnamed 2 August 7 1940
Unnamed 2 October 2 1860 Unnamed 3 September 19 1947
Unnamed 2 September 13 1865 Unnamed 1 September 4 1948
Unnamed 2 October 4 1867 Flossy 2 September 24 1956
Unnamed 1 September 5 1869 Audrey 4 June 27 1957
Unnamed 1 September 18 1877 Hilda 3 October 3 1964
Unnamed 2 August 23 1879 Betsy 3 September 10 1965
Unnamed 3 September 1 1879 Camille 5 August 17 1969
Unnamed 2 September 15 1882 Edith 2 September 16 1971
Unnamed 2 June 14 1886 Carmen 3 September 8 1974
Unnamed 3 October 12 1886 Babe 1 September 5 1977
Unnamed 1 October 19 1887 Bob 1 September 11 1979
Unnamed 1 September 23 1889 Danny 1 August 15 1985
Unnamed 2 September 7 1893 Juan 1 October 28 1985
Unnamed 4 October 2 1893 Florence 1 September 10 1988
Unnamed 1 September 12 1897 Andrew 3 August 26 1992
Unnamed 1 August 14 1901 Danny 1 July 18 1997
Unnamed 1 September 27 1906 Lili 1 October 3 2002
Unnamed 3 September 20 1909 Cindy 1 July 6 2005
Unnamed 1 August 17 1915 Katrina 3 August 29 2005
Unnamed 3 September 29 1915 Rita 3 September 24 2005
Unnamed 2 September 29 1917 Humberto 1 September 13 2007
Unnamed 3 August 7 1918 Gustav 2 September 1 2008
Unnamed 2 September 21 1920 Ike 2 September 13 2008
Source: Chronological List of All Hurricanes which Affected the Continental United States: 1851-2007[1]
Documentation of Atlantic Tropical Cyclones Changes in HURDAT[4]
Hurricane Gustav Public Advisory 32[5]
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199. Skyepony (Mod)
Watch that blob over Alabama..that may blow up coming off GA & run up the east coast.
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How does farmer's almanac make forecasts:

SE US:
July 2012
28th-31st. Humid, sticky weather, accompanied by hit-or-miss showers, thunderstorms.

August 2012
1st-3rd. Widely scattered showers, thunderstorms.

SC US:
August 2012
1st-3rd. Mostly fair. Hot and dry.

so far so good...
I know they arent too accurate but how do they do it.
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Quoting SFLWeatherman:
Q. What day will we have a TD or TS
A. TD today
B. TS today
C. TD tomorrow
D. TS tomorrow

C.
Member Since: July 6, 2010 Posts: 113 Comments: 31554
Member Since: September 30, 2007 Posts: 9 Comments: 15932
Member Since: August 6, 2011 Posts: 4 Comments: 37064
Quoting SFLWeatherman:
Q. What day will we have a TD or TS
A. TD today
B. TS today
C. TD tomorrow
D. TS tomorrow


I'm sticking with C. Later everyone!
Member Since: Posts: Comments:
Q. What day will we have a TD or TS
A. TD today
B. TS today
C. TD tomorrow
D. TS tomorrow
Member Since: May 23, 2012 Posts: 0 Comments: 4420

Number of recorded storms affecting Texas
Month Number of storms
June
7
July
7
August
18
September
21
October
13
November
2
[edit]
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Thanks Dr. Guess you are discounting the Northward CMC solution with a stronger system due to sheer issues. That NW turn, and break-away from the ITCZ, would have to come within the next 48 hours, so the GFS and most of the other models with a more southern track do seem more likely at this point; the CMC is an outlier at this point. That does mean a 50% of Ernesto over the weekend and we have to see what conditions await it in the Southern Caribbean at that time.
Member Since: August 8, 2006 Posts: 0 Comments: 8834
Quoting Stormchaser2007:
MODIS caught an excellent pass of 99L


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Quoting SFLWeatherman:
Why??
wind shear is weakining
Member Since: July 25, 2011 Posts: 0 Comments: 1102
Is 99L moving WNW??????
Member Since: May 23, 2012 Posts: 0 Comments: 4420
Quoting SFLWeatherman:
Is 99L moving WNW now???
Link


Maybe a little bit...I can't really tell..if it pulls out of the ITCZ and keeps its spin and convection....we might have something to actually TRACK.
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185. yoboi
Quoting galvestonhurricane:


Yeah, I deleted my comment because I left out several storms.


we had out fair share fo sure, i think it's fla yr...jmo
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MODIS caught an excellent pass of 99L
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Quoting yoboi:


lee, humberto,


Yeah, I deleted my comment because I left out several storms.
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182. yoboi
Quoting galvestonhurricane:
TX/LA have been threatened about every 4 years for the last decade:
2001: TS Allison
2005: Hurricane Rita
2008: Hurricanes Gustav and Ike
2012: ?


lilly, andrew
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181. yoboi
Quoting galvestonhurricane:
TX/LA have been threatened about every 4 years for the last decade:
2001: TS Allison
2005: Hurricane Rita
2008: Hurricanes Gustav and Ike
2012: ?


lee, humberto,
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Deleted
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178. yoboi
Quoting Stormchaser2007:




suprised they didn't spill any paint in the gulf...
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NEXSAT: Caribbean Viz Loop
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Is 99L moving WNW now???
Link
Member Since: May 23, 2012 Posts: 0 Comments: 4420
Member Since: August 6, 2011 Posts: 4 Comments: 37064
Member Since: May 23, 2012 Posts: 0 Comments: 4420
172. yoboi
Quoting RitaEvac:
TX/LA you've been warned......


la had lee anytime ya get lee the next yr is quiet...that's just statistics...
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Quoting AussieStorm:
@spann Car completely underwater at Lakeshore exit I-65 S

..huge rainmaker alright
Member Since: August 6, 2011 Posts: 4 Comments: 37064

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About

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