African tropical wave 99L slowly organizing

By: Dr. Jeff Masters , 1:26 PM GMT on July 31, 2012

Share this Blog
38
+

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

Reader Comments

Comments will take a few seconds to appear.

Post Your Comments

Please sign in to post comments.

or Join

Not only will you be able to leave comments on this blog, but you'll also have the ability to upload and share your photos in our Wunder Photos section.

Display: 0, 50, 100, 200 Sort: Newest First - Order Posted

Viewing: 1771 - 1721

Page: 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 | 16 | 17 | 18 | 19 | 20 | 21 | 22 | 23 | 24 | 25 | 26 | 27 | 28 | 29 | 30 | 31 | 32 | 33 | 34 | 35 | 36 | 37 | 38 | 39 | 40 | 41 | 42 | 43 | 44 | 45 | 46 | 47 | 48Blog Index

1771. msphar
Looking back to Ivan 2004, by this Longitude Ivan was a cat 2 and growing more evil everyday. Tonight, I have concerns for the survival of 99L what a difference a decade (or thereabouts) makes.
Member Since: Posts: Comments:
Quoting ilovehurricanes13:
I see some wind shear next to invest 99L


That will change in the next hours,i think since the 99L is not convecting in the past hours the NHC maybe stay in 50% the question is RED OR Stay with orange?
Member Since: June 20, 2012 Posts: 0 Comments: 2169
1769. nigel20
Quoting Gearsts:
Nah what are you all saying?! Here in PR we have the best power grid in the caribbean ;)

Most of the production plants in Jamaica are outdated and are operating inefficiently. A 360MW LNG plant will be built and commissioned by 2015 to improve production and transmission of electricity.
Member Since: Posts: Comments:
Microsoft kills hotmail.... gone....

Now it is outlook.com

Link
Member Since: Posts: Comments:
Quoting ilovehurricanes13:
I see some wind shear next to invest 99L


I think the wind shear is decreasing just in front of 99L

Member Since: Posts: Comments:
1766. Gearsts
Member Since: Posts: Comments:
Quoting islandgirls:
what are the chances of us getting rain here in the Northern islands?


From 99L? I'd say about 60%.
Member Since: Posts: Comments:
Going to bed... good night, y'all.
Member Since: August 1, 2011 Posts: 28 Comments: 8041
im very very new to this... flying from NY to Orlando on 8/10.... should i be alittle concerned about this yet? or does a system like 99L have no chance of hitting the mainland florida?
Member Since: Posts: Comments:
what are the chances of us getting rain here in the Northern islands?
Member Since: Posts: Comments:
I think this one is gonna end up in the Hot Tub (Gulf)....I'm sure I'm wishcasting, but it hasn't shown too much of a N'ward trend at all. I would say the W. Caribbean and then folks living on the Coast of the hot tub should watch this one!!
Member Since: Posts: Comments:
00z GFS 78 hrs.

Member Since: Posts: Comments:
.
Member Since: Posts: Comments:
1757. Gearsts
Quoting sunlinepr:


Like the blackout of the other day, when they fired the executive manager.... Strange.... the only time 80% of the island went off, and they fixed it in 4 hrs....
Nah what are you all saying?! Here in PR we have the best power grid in the caribbean ;)
Member Since: Posts: Comments:
Quoting CaicosRetiredSailor:



google
"is the mjo a kelvin wave"
for some papers and discussion



Thanks, that helped, although it's a little too late at night for me for differential equations, however I think the general idea is that kelvin waves are the vehicle that moves the MJO (probably an overly simplistic explanation).
Member Since: Posts: Comments:
Member Since: Posts: Comments:
Quoting 954FtLCane:


just his/her opinion. You had yours at a cat 3 and would not have enjoyed people telling you you're nuts now would you?

I personally don't see 99L as a strong storm but it is way way too early to tell.

I agree that a CAT 3 would be a little off for now yeah but what he/she said yaeh kinda nuts it just the DMIN plus it not really warming anymore its cooling red top are not starting to pop
Member Since: Posts: Comments:
1753. Gearsts
Quoting ilovehurricanes13:
saying goodbye to invest 99L its going to die out soon the t.storms will go away.. its going down to 40% at 2am
Just chill and give it time.
Member Since: Posts: Comments:
1752. nigel20
Quoting kmanislander:
Time to turn in for me. Have a great evening all and no peeking at 99L until sunrise

Same to you
Member Since: Posts: Comments:
Quoting JLPR2:


I find it strange that I still have power during a heavy thunderstorm but somehow loose it on a sunny day. LOL!


Like the blackout of the other day, when they fired the executive manager.... Strange.... the only time 80% of the island went off, and they fixed it in 4 hrs....
Member Since: Posts: Comments:
5 day java loop of the wind shear
shear has really come down near the Lesser Antilles and the Eastern Caribbean.
Member Since: Posts: Comments:
1749. Gearsts
Quoting wunderkidcayman:

next monday or tuesday


was warming now cooling see the red spot before it was just yellow


nah
The overall structure of clouds is warming.
Member Since: Posts: Comments:
My crystal ball says this one blows through the Southern Islands as a TS...then it's followed by dire predictions here of Ivan part deux despite caution by the NHC on shear, which is followed by the cyclone slipping a bit in the graveyard, and in the end we're left looking for the remains of Ernesto somewhere in CA. Hopefully it won't linger too long over land causing flooding.
Member Since: Posts: Comments:
Quoting kmanislander:
no peeking at 99L until sunrise


Only if you give me a cookie.
Member Since: Posts: Comments:
You sure can see the shear making it's presence.
Member Since: May 22, 2010 Posts: 0 Comments: 907
I'll be right back
Member Since: Posts: Comments:
Quoting wunderkidcayman:

umm dude lets put it kindly

YOU ARE NUTS


just his/her opinion. You had yours at a cat 3 and would not have enjoyed people telling you you're nuts now would you?

I personally don't see 99L as a strong storm but it is way way too early to tell.
Member Since: Posts: Comments:
1743. JLPR2
Quoting HuracanTaino:
Agree, in Puerto Rico you can get a "black out at any moment".... when you least expected.


I find it strange that I still have power during a heavy thunderstorm but somehow loose it on a sunny day. LOL!
Member Since: Posts: Comments:
Quoting Huracaneer:


I think its Dmin, notice how everything else in the basin is also winding down (the Florida, blob, the Dominican blob, and pretty much all convection). You have to have a pretty well established storm to go through Dmin without losing convection (which 99L is not yet).


Some people don't understand the patience required for tropical blob watching. It's a good thing that guy's not a professional forecaster.
Member Since: Posts: Comments:
Time to turn in for me. Have a great evening all and no peeking at 99L until sunrise
Member Since: Posts: Comments:
Quoting ilovehurricanes13:
saying goodbye to invest 99L its going to die out soon the t.storms will go away.. its going down to 40% at 2am

umm dude lets put it kindly

YOU ARE NUTS
Member Since: Posts: Comments:
Quoting ilovehurricanes13:
saying goodbye to invest 99L its going to die out soon the t.storms will go away.. its going down to 40% at 2am


I think its Dmin, notice how everything else in the basin is also winding down (the Florida, blob, the Dominican blob, and pretty much all convection). You have to have a pretty well established storm to go through Dmin without losing convection (which 99L is not yet).
Member Since: Posts: Comments:
Quoting HuracanTaino:
Agree, in Puerto Rico you can get a "black out at any moment".... when you least expected.


We dont have to have a hurricane moving thru to have blackouts as with some gusts (25-30 mph) it goes out.
Member Since: Posts: Comments:
Got a good spin to it, DMAX is a couple hours away, lets see if it can organize further and close off a circulation then it will be go time.

Member Since: Posts: Comments:
Quoting KoritheMan:


...



lol..ah come on...post it :) j/k
Member Since: August 16, 2007 Posts: 1 Comments: 2351
1735. Skyepony (Mod)
Quoting TropicalAnalystwx13:

The reliable LGEM model says different.



LGEM did really well in the 24hr 99L model verification. LGEM & SHIP are both leading in best intensity model on 99L.
Member Since: Posts: Comments:
Quoting 19N81W:
So if it does come into the wcarib we are looking at 6 to 7 days for cayman? If....

next monday or tuesday

Quoting Gearsts:
Warming clouds tops...

was warming now cooling see the red spot before it was just yellow

Quoting stormchaser19:
is the cell in front of 99L, inhibiting any intensification ?


nah
Member Since: Posts: Comments:
1733. nigel20
Quoting DDR:

Hey Nigel,the last storm to affect us was Thomas in 2010,feeder bands caused some flooding and landslips in the North eastern Trinidad and Tobago.

Quoting DDR:
Nigel we usually get some degree of flooding/landslips when tropical systems pass close by.

Thanks for the info.
Member Since: Posts: Comments:
Quoting ilovehurricanes13:
saying goodbye to invest 99L its going to die out soon the t.storms will go away.. its going down to 40% at 2am


...
Member Since: Posts: Comments:
Quoting JLPR2:


I'm happy to say power never went out in my house.
Huzzah! XD
Wait for it, I will probably loose power on a sunny day.
Agree, in Puerto Rico you can get a "black out at any moment".... when you least expected.
Member Since: Posts: Comments:
Member Since: Posts: Comments:
Good grief.
Member Since: August 16, 2007 Posts: 1 Comments: 2351
Quoting Huracaneer:


There is still a lot of good people in this blog, Levi for one and (knock on wood) the trolls haven't been too horrible lately (although he whose name should not be mentioned but think shower curtains) paid us a visit lately. Yeah it took me a while to feel like a could post without making a total fool of myself (now just a partial fool). By the way for anybody out there, is the MJO considered a Kelvin wave?



google
"is the mjo a kelvin wave"
for some papers and discussion

like...

JOURNAL OF GEOPHYSICAL RESEARCH, VOL. 116, D18102, 13 PP., 2011
doi:10.1029/2011JD015925

Kelvin wave time scale propagation features of the Madden-Julian Oscillation (MJO) as measured by the Chen-MJO index

Key Points
A Kelvin wave signal has been extracted from time series of the Chen-MJO index
The signal is seen in correlation analyses of indexed MJO strength increases
At a given longitude the signal tends to mark the initial stages of MJO growth


Member Since: Posts: Comments:
1726. nigel20
Quoting Tropicsweatherpr:


Plenty of moisture there,but the sal is not far away to the north.

Yeah... tomorrow could be a very interesting day for 99L.
Member Since: Posts: Comments:
is the cell in front of 99L, inhibiting any intensification ?

Member Since: June 20, 2012 Posts: 0 Comments: 2169
1724. DDR
Nigel we usually get some degree of flooding/landslips when tropical systems pass close by.Ivan was the worse in can remenber,it flooded our main highway on one side after 3 days of heavy rains.
Member Since: Posts: Comments:
Quoting Gearsts:
Warming clouds tops...


Let's see what occurs in a few hours when DMAX arrives.
Member Since: Posts: Comments:
1722. DDR
Quoting nigel20:

Hey DDR! Which was the last storm to affect Trinidad?
I know you guys are generally spared most of the effects of tropical storms and hurricanes.

Hey Nigel,the last storm to affect us was Thomas in 2010,feeder bands caused some flooding and landslips in the North eastern Trinidad and Tobago.
Member Since: Posts: Comments:
Quoting Huracaneer:


There is still a lot of good people in this blog, Levi for one and (knock on wood) the trolls haven't been too horrible lately (although he whose name should not be mentioned but think shower curtains) paid us a visit lately. Yeah it took me a while to feel like a could post without making a total fool of myself (now just a partial fool). By the way for anybody out there, is the MJO considered a Kelvin wave?


Yep...great bloggers here. Over the years there has been drama and trolls..but WU is still the best!
Member Since: August 16, 2007 Posts: 1 Comments: 2351

Viewing: 1771 - 1721

Page: 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 | 16 | 17 | 18 | 19 | 20 | 21 | 22 | 23 | 24 | 25 | 26 | 27 | 28 | 29 | 30 | 31 | 32 | 33 | 34 | 35 | 36 | 37 | 38 | 39 | 40 | 41 | 42 | 43 | 44 | 45 | 46 | 47 | 48Blog Index

Top of Page

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.