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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2320. pottery
For Information.

A very good site in Barbados.

www.brohavwx.com

Radar, lightening strikes, whatnot and stuff.
Member Since: Posts: Comments:
Quoting Houstonweathergrl:
Florida,you can HAVE this storm. We are still recovering from IKE in this area and just don't want death and destruction...not that anyone does.

I am however grateful for all the rain we've received. Last summer was just brutal. Still lots of dead trees and it wouldn't take a bad storm to knock them over.
Ike was a bad bad.I heard some parts are still deserted.Is that true?.
Member Since: August 14, 2010 Posts: 10 Comments: 16968
Quoting LargoFl:
This is for those folks who have yet to experience a hurricane and WHAT damage they can go..and in what Category...........amazing........................ .............Based on the Saffir-Simpson scale:

A Category Three Hurricane, sustained winds of 111-130 mph will cause extensive damage. Some structural damage to houses and buildings will occur with minor amount of wall failure%u2026

Based on a Category Four Hurricane, sustained winds 131-155 mph, extremely dangerous winds causing devastating damage are expected. Some wall failures with some complete roof failures on houses will occur%u2026

Based on the test results in comparison to the minimum wind speed of a Category Four Hurricane, 131 mph. Hurricane Harness� provides a 20% increase or equivalent to 26 mph in wind speed resistance before roof failure begins.

Summary:

Combine 131 mph 26 mph = 157 mph; a Category Five hurricane
.............im thinking..should i get roof tie downs..when i found this

I saw damage by Andrew in person...unbelieveable.
Member Since: August 2, 2011 Posts: 0 Comments: 1911
Quoting ackee:
When will 99L be upgraded ?


A 5pm
B 11pm
C 5Am tomorrow
D 11Am tomorrow



B
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Quoting Pocamocca:

And convection should have no problem increasing today, especially near the southern half of the system.


Does the Kelvin wave help with ventilation or atmospheric lift or something? I think I read that somewhere...
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Florida,you can HAVE this storm. We are still recovering from IKE in this area and just don't want death and destruction...not that anyone does.

I am however grateful for all the rain we've received. Last summer was just brutal. Still lots of dead trees and it wouldn't take a bad storm to knock them over.
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2312. GetReal


A different look at 99L.
Member Since: July 4, 2005 Posts: 204 Comments: 8871
2311. GetReal
Quoting washingtonian115:
If MOD was correct we'd have a cat 2 by now.Lol.


Like many of the other models , it has trouble with handling intensity.?.
Member Since: July 4, 2005 Posts: 204 Comments: 8871
If the CIMSS shear analysis is 100% correct, (which it never is) then there is about 30 knots on the northern edge of the circulation.

All this has to do is halt the northern movement for a bit and it will benefit greatly from some strong ventalation.
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Quoting HurricaneHunterJoe:


Is it completely out of the monsoon trof yet?


IMO not totally, but it is in the process of detaching. You can even see that on the vortex maps and satellite representations. You can see the trough kicking out to the west in front of it all the way to the islands. Then you can see the moisture field its also wrapping into it from the east back towards the rest of the ITCZ.



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Quoting Waltanater:
A
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2306. LargoFl
This is for those folks who have yet to experience a hurricane and WHAT damage they can go..and in what Category...........amazing........................ .............Based on the Saffir-Simpson scale:

A Category Three Hurricane, sustained winds of 111-130 mph will cause extensive damage. Some structural damage to houses and buildings will occur with minor amount of wall failure%u2026

Based on a Category Four Hurricane, sustained winds 131-155 mph, extremely dangerous winds causing devastating damage are expected. Some wall failures with some complete roof failures on houses will occur%u2026

Based on the test results in comparison to the minimum wind speed of a Category Four Hurricane, 131 mph. Hurricane Harness provides a 20% increase or equivalent to 26 mph in wind speed resistance before roof failure begins.

Summary:

Combine 131 mph 26 mph = 157 mph; a Category Five hurricane
.............im thinking..should i get roof tie downs..when i found this
Member Since: August 6, 2011 Posts: 4 Comments: 38423
The well-advertised departure from the ITCZ has occurred, but in turn 99L has lost its symmetrical shape of convection due to dry air entrainment and high shear on the northern side (also well-advertised). The circulation is there for a TC, but the NHC has to make the choice on whether there is enough convection to classify Ernesto.

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Kelvin wave has progressed a bit slower over the past 12 hours.

Should be over 99L later tonight into tomorrow.

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Quoting Stormchaser2007:
Excellent MW pass on 99L.

Justifies a relocation of the LLC farther north. If it can stay under the convection today, this should begin to take advantage of being father away from the equator.



This is an excellent product! On the shortwave loop you can see it, too.
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Quoting SFLWeatherman:
Maybe a TD by 11AM

Today? Nah.
the ATCF doesn't say so. And it has only 60% chance of forming within the next 48 hours.

Just out of curiosity, why doesn't the NHC say 2 days instead of 48 hours and 1 day instead of 24 hours?
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2301. GetReal


99L should track generally towards the west or slightly WNW the next 72 hours in IMO.
Member Since: July 4, 2005 Posts: 204 Comments: 8871
/
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Nother pass...

Looks like a very obvious LLC

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Putting my two cents in--maybe three cents...looks like

99l is BOC bound. However the stronger it gets, the

better chance it gets "pulled" more northerly before

reaching the BOC. There is plenty of hot water on that

route. Should be interesting.
Member Since: August 2, 2011 Posts: 0 Comments: 1911
The U.S can not afford to have a hurricane headed for us.No one wants that after a long break :(.Opps Am I missing something?..It starts with a I...
Member Since: August 14, 2010 Posts: 10 Comments: 16968
Good morning everyone! Visible imagery and Dvorak suggest 99L is getting close to TD status.

Looking at water vapor numerical guidance this morning suggests that as long as 99L doesn't travel north of 15 degrees latitude before it gets to 65W, the upper level shear should be pretty favorable.

Upper level westerlies are located closeby to the north with flow around a large, nearly stationary upper level low near 27N44W, though they shouldn't get any closer to the CoC as 99L continues its WNW heading away from the low.

About the only thing I see on model guidance over the next two days that is unfavorable is some moderately dry mid/upper levels. Once in the eastern Caribbean, there will be a bit more low/mid level shear, and continued dry air. I'm a bit surprised by the low intensity guidance by all of the dynamical models, but out of respect for them, I would think that a blend between their intensity and the latest SHIPS guidance would be reasonable.

Given that, I'd say TD later today (11am/5pm) then TS at some point tomorrow. I see the storm around 50 mph as it crosses into the eastern Caribbean and only very slow intensification until it reaches 75W or so...
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Maybe a TD by 11AM
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2294. LargoFl
Link.....................Hurricane Andrew and what it did to Homestead florida....gee
Member Since: August 6, 2011 Posts: 4 Comments: 38423
wow is that 50 to 60MPH!!
Quoting Stormchaser2007:
SCAT pass on 99L.

Seems the LLC is close to the edge of the convection.

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Excellent MW pass on 99L.

Justifies a relocation of the LLC farther north. If it can stay under the convection today, this should begin to take advantage of being father away from the equator.

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From me
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Quoting SLU:
All that's needed to conclude the formalities now is a good ASCAT pass to confirm its structure.


What are they having problems with? I can't get ASCAT or OSCAT to load.
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Interested to hear Levi's opinion now that the Caribbean shouldn't kill it or weaken it dramatically like it looked like a few days ago. He said yesterday he'd have a tidbit out today.
Member Since: July 6, 2010 Posts: 113 Comments: 31996
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Quoting GeorgiaStormz:
you know if this recurves it will make it to TX/LA ahead of Aug 16-19.
I think it is safe to say they have blown that forecast :)
might.not.be.a.straight.course.could.do.all.sorts .of.thingsgeorgiaz
Member Since: September 11, 2010 Posts: 1 Comments: 4567
Quoting TropicalAnalystwx13:

And it jumped .5N...


I was thinking earlier maybe 11.0n, I can live with 10.7
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2285. Grothar
The next flare-up of convection should begin again in the NW quadrant.

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Quoting ackee:
When will 99L be upgraded ?


A 5pm
B 11pm
C 5Am tomorrow
D 11Am tomorrow
A
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SCAT pass on 99L.

Seems the LLC is close to the edge of the convection.

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Quoting ncstorm:
here is the 00z CMC with visualizing colors dooming Florida







Anyone got the latest GFS at 216-240 time frame handy?
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Gotta get to some work and will check in around lunch, but, the potential trajectory issue will be resolved in about 48-72 hours when the storm reaches depression or TS status, the hunters can get in to sample the surrounding synoptic conditions, and fresh data is fed into the models. We should have a better picture by Friday and the NHC track will of course reflect the consensus model guidance at that time. This storm might surprise lots of folks, intensity wise, whether it tracks into the Caribbean or just north of the Island chain..........It's headed into very warm and untapped SST's all the way in.
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Quoting LargoFl:
..that was a futurecast of what the model see's friday.. for florida.....that swirl just might be what was over PR yesterday maybe
Thank you!!,that is what I thought!!,looking at the Atlantic rainbow loop,I can see there is less convention today from that tropical wave than yesterday,but at the same time is getting moisture and it's getting rounded and convention start to fire up again,so will see what happens?,anything North of the island this time a year is something to watch.
Member Since: August 28, 2006 Posts: 0 Comments: 609
2277. Grothar
Seems to be gaining a little more latitude.

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2276. HadesGodWyvern (Mod)
Japan Meteorological Agency
Tropical Cyclone Advisory #45
SEVERE TROPICAL STORM DAMREY (1210)
21:00 PM JST August 1 2012
=============================================

SUBJECT: Category Two Typhoon In East China Sea

At 12:00 PM UTC, Severe Tropical Storm Damrey (975 hPa) located at 30.8N 128.7E has 10 minute sustained winds of 55 knots with gusts of 80 knots. The cyclone is reported as moving west northwest at 20 knots.

Dvorak Intensity: T3.5

Storm Force Winds
====================
40 NM from the center

Gale Force Winds
=================
300 NM from the center in northeast quadrant
180 NM from the center in southwest quadrant

Forecast and Intensity
==========================

24 HRS: 34.9N 121.4E - 50 knots (CAT 2/Severe Tropical Storm) - Yellow Sea
48 HRS: 37.7N 119.4E - 40 knots (CAT 1/Tropical Storm) - Bohai Sea
72 HRS: 41.0N 122.0E - Tropical Depression Overland northeastern District of China

Japan Meteorological Agency
Tropical Cyclone Advisory #45
TYPHOON SAOLA (1209)
21:00 PM JST August 1 2012
=============================================

SUBJECT: Category Three Typhoon South Of Okinawa

At 12:00 PM UTC, Typhoon Saola (960 hPa) located at 23.9N 122.8E has 10 minute sustained winds of 70 knots with gusts of 100 knots. The cyclone is reported as moving northwest at 7 knots.

Dvorak Intensity: T4.5

Storm Force Winds
=================
60 NM from the center

Gale Force Winds
================
400 NM from the center in southeast quadrant
300 NM from the center in northwest quadrant

Forecast and Intensity
==========================

24 HRS: 26.1N 121.5E - 80 knots (CAT 3/Strong Typhoon) - East China Sea
48 HRS: 29.1N 119.2E - 35 knots (CAT 1/Tropical Storm) - Overland Central China
72 HRS: 31.0N 115.0E - Tropical Depression Overland Central China
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So yesterday I was watching Denis Philips on live weather chat(I would love it if the doc could do one) and he totally dissed the Canadians and their model. "What do Canadians know about hurricanes","they know about snow and beer though"
Member Since: August 14, 2010 Posts: 10 Comments: 16968
2274. LargoFl
. .................................as you can see..right now the models are ALL OVER THE PLACE with 99l.....a few more days they should come into better agreement..remembering this has NOT yet formed into a tropical storm
Member Since: August 6, 2011 Posts: 4 Comments: 38423
FWIW, a track between the HWRF and TVCN would have to potential for 99L to gain enough speed for the trades to not affect it, and for the UL shear to not be a significant player.

Have to look at some more variables though, but I'm very surprised by the change in tune.
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Quoting SFLWeatherman:
What is going on no 8AM Model why????


May be related to computer issues......


NOUS42 KWNO 011048
ADMNFD


SENIOR DUTY METEOROLOGIST NWS ADMINISTRATIVE MESSAGE
NWS NCEP CENTRAL OPERATIONS CAMP SPRINGS MD
1043Z WED AUG 01 2012


NCEP`S PRIMARY SUPER COMPUTER WENT DOWN...WE ARE CURRENTLY
SWITCHING TO THE BACKUP...THERE WILL BE DELAYS IN NCEP MODEL
PRODUCTION BECAUSE OF THIS...MORE DETAILS WILL BE PROVIDED AS
THEY ARE AVAILABLE.


06Z GFDL just finished, the HWRF is still running.
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2271. GetReal


Nice in flow at the low levels, and ventilating in all quads in the UL.
Member Since: July 4, 2005 Posts: 204 Comments: 8871

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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.