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: 71 - 21

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

Quoting ncstorm:
I know everyone is focus on 99l but there are several models predicting development off of SC/NC from the disturbance currently located in GA/Alabama..


Yah, i looked at those but there is too much shear for tropical development in spite of their tropical airmass origins. Wet, mild and maybe a little breezy for Nova Scotia next couple of days. One always havs to be careful with convective feedback in high PW systems - models tend to overdo convection which, in turn, overdoes vorticity.
Member Since: Posts: Comments:
Quoting GetReal:



In spite of the alleged hostile conditions, the PR system (blob) is looking better organized with each passing hour. Impressive complex over AL.

NHC could give it a Near 0% chance at 2PM. lol
Does it have a spin?
Member Since: Posts: Comments:
I am confused. :(
Member Since: Posts: Comments:
Quoting LargoFl:
..if you look and this radar..this system is headed for the gulf..i dont see any turn towards the atlantic just yet
Member Since: August 6, 2011 Posts: 4 Comments: 33344
Quoting RTSplayer:
Science Lesson:

What guys are supposed to want, Chapter 2.



Candice Swanepoel

Rainbow Zebra Oh My...



Bilingual
Wants children
Dating the same guy for six years. Good for her.


dude really?
admins a'comin for you :)
Member Since: February 11, 2012 Posts: 0 Comments: 9452
Quoting Hurricane1956:
Amazing!!!!! what a nice picture!!!.
..I just wonder where common sense went..she see's that sky..lightning around and she's on the beach jogging..geez
Member Since: August 6, 2011 Posts: 4 Comments: 33344
Member Since: August 6, 2011 Posts: 4 Comments: 33344
Quoting LargoFl:
...........beach in bay county florida,just look at that sky
Amazing!!!!! what a nice picture!!!.
Member Since: Posts: Comments:



In spite of the alleged hostile conditions, the PR system (blob) is looking better organized with each passing hour. Impressive complex over AL.
Member Since: July 4, 2005 Posts: 204 Comments: 8802

Quoting unknowncomic:
Looking at the GFS prediction of the shear in the Caribbean compared to the shear (from the experimental cyclone genesis sie), Hispanola and Haiti at 174 hours, 99l is much better off on the southerly track if it can hold together..



Member Since: August 2, 2011 Posts: 0 Comments: 1722
Quoting LargoFl:
..hi NC I am watching this one very closely..do you see how HUGE this one is..


Very!..its supposed to move off the coast in 48 hours..its packing a punch thats for sure right now
Member Since: Posts: Comments:
Interesting couple of impulses off the eastern seaboard next couple of days. The first, south of NYC this morning is baroclinic by imagery, but nearly barotropic by airmass in a very high 1000-500 mb thickness environment. GEM deepens it a bit offshore then moves it into Nova Scotia tomorrow where rain should be quite heavy. The next develops off Hatteras tomorrow in the base of the weak upper trough but in a 576dm thickness environment...typically a tropical airmass too.
Member Since: Posts: Comments:
Quoting ncstorm:
I know everyone is focus on 99l but there are several models predicting development off of SC/NC from the disturbance currently located in GA/Alabama..its supposed to enter into the Atlantic off the NC/SC coast and ride up both coasts..

on the verge of warm core..could be subtropical

GFS

NOGAPS

CMC
..hi NC I am watching this one very closely..do you see how HUGE this one is..
Member Since: August 6, 2011 Posts: 4 Comments: 33344
. .....................this is amazing
Member Since: August 6, 2011 Posts: 4 Comments: 33344
I know everyone is focus on 99l but there are several models predicting development off of SC/NC from the disturbance currently located in GA/Alabama..its supposed to enter into the Atlantic off either the NC or SC coast and ride up both coasts depending on where it exits off

on the verge of warm core..could be subtropical

GFS

NOGAPS

CMC
Member Since: Posts: Comments:
Quoting Pocamocca:

That's me!!! ;)
..LOL
Member Since: August 6, 2011 Posts: 4 Comments: 33344
Quoting LargoFl:
...........beach in bay county florida,just look at that sky
Very ominous looking.Wow.
Member Since: August 14, 2010 Posts: 10 Comments: 15707

Quoting Stormchaser2007:


24 knots of shear in the heart of the Caibbean. This doesn't even account for the low level winds, which are screaming.

The way conditions are looking now, things are a bit dim for 99L in the extended range.


SHEAR (KT) 7 5 3 7 4 4 8 7 11 14 14 20 24

LAT (DEG N) 9.3 9.6 9.8 10.0 10.2 10.5 10.9 11.3 11.8 12.7 13.5 14.7 15.7
LONG(DEG W) 39.6 40.9 42.1 43.3 44.5 46.7 48.9 51.0 53.5 56.0 58.8 61.6 64.3

Member Since: August 2, 2011 Posts: 0 Comments: 1722
...........beach in bay county florida,just look at that sky
Member Since: August 6, 2011 Posts: 4 Comments: 33344
While we're watching 99L the disturbance behind it is interesting as well.
Member Since: August 14, 2010 Posts: 10 Comments: 15707
Quoting unknowncomic:
Over time, Caribbean shear is less than the shear on the northerly track for 99l.


24 knots of shear in the heart of the Caribbean. This doesn't even account for the low level winds, which are screaming.

The way conditions are looking now, things are a bit dim for 99L in the extended range.


SHEAR (KT) 7 5 3 7 4 4 8 7 11 14 14 20 24

LAT (DEG N) 9.3 9.6 9.8 10.0 10.2 10.5 10.9 11.3 11.8 12.7 13.5 14.7 15.7
LONG(DEG W) 39.6 40.9 42.1 43.3 44.5 46.7 48.9 51.0 53.5 56.0 58.8 61.6 64.3
Member Since: June 9, 2007 Posts: 4 Comments: 15718
Quoting Pocamocca:
Interesting that many of these old-time heat records for many sites in the Great Plains and Midwest occurred nearly 100 years ago.
Well, Little Rock's all-time heat record was set last year, not "nearly 100 years ago". Too, last summer was the warmest summer ever for several states, and in fact was the warmest summer ever for any state.

The indisputable bottom line fact is this: while there were some warm temperature spikes back in the 1930s, overall the nation is far warmer now than it was then--and it's getting hotter all the time.
Member Since: Posts: Comments:
Link
Central Atlantic Visible
Member Since: Posts: Comments:
BULLETIN - IMMEDIATE BROADCAST REQUESTED
SEVERE THUNDERSTORM WARNING
NATIONAL WEATHER SERVICE BIRMINGHAM AL
844 AM CDT TUE JUL 31 2012

THE NATIONAL WEATHER SERVICE IN BIRMINGHAM HAS ISSUED A

* SEVERE THUNDERSTORM WARNING FOR...
JEFFERSON COUNTY IN ALABAMA...
SOUTHWESTERN ST. CLAIR COUNTY IN ALABAMA...
NORTHERN SHELBY COUNTY IN ALABAMA...
CENTRAL TALLADEGA COUNTY IN EAST CENTRAL ALABAMA...
EASTERN WALKER COUNTY IN ALABAMA...

* UNTIL 930 AM CDT

* AT 840 AM CDT...THE NATIONAL WEATHER SERVICE INDICATED A LINE OF
SEVERE THUNDERSTORMS CAPABLE OF PRODUCING DAMAGING WINDS IN EXCESS
OF 60 MPH. THESE STORMS WERE LOCATED ALONG A LINE EXTENDING FROM
SMITH DAM TO FULTONDALE TO PELL CITY...AND MOVING SOUTHEAST AT 25
MPH.

* LOCATIONS IMPACTED INCLUDE...
LEEDS...IRONDALE...CORDOVA...SUMITON...DORA...MOUN TAIN BROOK...
BIRMINGHAM AND HOMEWOOD.

WINDS OF 60 TO 70 MPH WILL BREAK LARGE TREE LIMBS AND CAUSE SOME
DAMAGE...ESPECIALLY TO SMALLER STRUCTURES.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

FOR YOUR PROTECTION...MOVE TO AN INTERIOR ROOM ON THE LOWEST FLOOR OF
YOUR HOME OR BUSINESS.
Member Since: August 6, 2011 Posts: 4 Comments: 33344
Quoting LargoFl:
..what may be dangerous with this alabama storm..there is a high in the gulf..when this storm gets into the gulf..there is a stiff eastbound wind that may well push this INTO northern or central florida later on, my hope is it doesnt sit in that hot water..86 degree's for too long..we do not need..another debby here


its just a bunch of rain
Member Since: February 11, 2012 Posts: 0 Comments: 9452
Over time, Caribbean shear is less than the shear on the northerly track for 99l.
Member Since: August 2, 2011 Posts: 0 Comments: 1722
Big TUTT.

Member Since: Posts: Comments:
Quoting shmdaddy:
Morning all! Sitting here north of Destin, FL. Awesome thunderstorm just came through here. No wind, just lots of lightning bolts! Looks like more rain on the way. Guess I picked the wrong day to take off!
..stay safe up there
Member Since: August 6, 2011 Posts: 4 Comments: 33344
Quoting LargoFl:
..what may be dangerous with this alabama storm..there is a high in the gulf..when this storm gets into the gulf..there is a stiff eastbound wind that may well push this INTO northern or central florida later on, my hope is it doesnt sit in that hot water..86 degree's for too long..we do not need..another debby here
Member Since: August 6, 2011 Posts: 4 Comments: 33344
Member Since: Posts: Comments:
Now IF conditions are favorable in the caribbean in the next few days then watch out,because TCHP is high with some spots getting near the upper 80's.We'll just see how conditions play out.
Member Since: August 14, 2010 Posts: 10 Comments: 15707
Morning all! Sitting here north of Destin, FL. Awesome thunderstorm just came through here. No wind, just lots of lightning bolts! Looks like more rain on the way. Guess I picked the wrong day to take off!
Member Since: Posts: Comments:
Member Since: August 6, 2011 Posts: 4 Comments: 33344
Quoting Pocamocca:
That did strike me odd that the run up to the CONUS would be more hostile. But if you really digest all the dynamics in play...it does make sense.

Either way, I think it's RIP for 99L within the next 4 days.


I disagree.. while the east Caribbean can wreck a storm.. if it can survive till it gets to the west Caribbean.. it will have a chance..Anyways.. in 4 days it will just be approaching the islands
Member Since: Posts: Comments:
Maybe Hispanola dooms it.
Member Since: August 2, 2011 Posts: 0 Comments: 1722
Even if 99L can develop within the next 72 hours, it will still have to deal with the insane low level flow that rules the Caribbean. That LL flow is the reason that Caribbean SST's have been a little below normal. The TUTT will keep 99L's circulation a bit tilted up until it reaches the islands, but once it hits the higher shear with a semi-disorganized circulation...oof

Member Since: June 9, 2007 Posts: 4 Comments: 15718
Quoting reedzone:
The storm is less likely to survive if it heads northwest towards the U.S.

O.o .... what??


thats what I said as well..
Member Since: Posts: Comments:
Quoting washingtonian115:
It was also interesting that some of the models were showing a favorable environment.I'm getting confused!!.If shear is going to be favorable in the caribbean it needs to weaken from what it is now.


The point is:
The evironment before the caribbean is more favorable for development than the one moving northwest to the US due to SAL and shear above 99L
However, the environment in the caribbean is deadly to any TC and is much worse than a track NW towards the US.

Dr Masters is more concerned about the effects of a TS on the lesser antilles, than he is about what happens in the caribbean, so a straight west path will lead to a better ernesto than a NW one, at least in the short to medium range.
Member Since: February 11, 2012 Posts: 0 Comments: 9452
Member Since: August 6, 2011 Posts: 4 Comments: 33344
The storm is less likely to survive if it heads northwest towards the U.S.

I thought the models that take it northwest increases it in intensity..the models that keep it west dissapates it..
Member Since: Posts: Comments:
I think the Doc is taking into account that the TUTT will set up over the Bahamas making conditions hostile.StormW said something like this yesterday that if it went through the caribbean it'll have a better chance of surviving.
Member Since: August 14, 2010 Posts: 10 Comments: 15707
The storm is less likely to survive if it heads northwest towards the U.S.

O.o .... what??
Member Since: Posts: Comments:
Member Since: August 6, 2011 Posts: 4 Comments: 33344
thx dr masters
Member Since: February 11, 2012 Posts: 0 Comments: 9452
Quoting washingtonian115:
It was also interesting that some of the models were showing a favorable environment.I'm getting confused!!.If shear is going to be favorable in the caribbean it needs to weaken from what it is now.



well sure.. its 5-6 days away from the Caribbean right now
Member Since: Posts: Comments:
Derived from (NHC) ATCF data for 99L for 31July12pmGMT:

MinimumPressure had held at 1010millibars
MaximumSustainedWinds had held at 20knots(23mph)37km/h
Its travel-direction&speed had held to 277.8degreesWest at 17.2mph(27.7km/h)

For those who like to visually track 99L's path...
SLU is St.Lucia :: BGI is Barbados :: TAB is Tobago :: NTO is SantoAntao,CapeVerde

The kinked line represents 99L's initial 42hours of travel.
The middle line-segment represents 99L's most recent 6hours of travel.

The longest line is a straightline projection through 99L's 2 most recent positions to a coastline.
On 31July12pmGMT, 99L was headed toward passing over SaintGilesIsland,Trinidad&Tobago in ~3days10hours from now

Copy&paste slu, tab, bgi, nto, 8.7n34.1w- 8.7n34.4w- 8.7n34.7w- 8.7n35.1w- 8.7n35.5w- 8.7n35.8w- 8.9n36.6w- 9.1n38.1w- 9.3n39.6w, 9.1n38.1w-11.359n60.513w into the GreatCircleMapper for more information
The previous mapping for comparison.
Member Since: Posts: Comments:
Quoting GeoffreyWPB:
........its amazing, this storm in Alabama is HUGE..and so much better looking and maybe more destructive than 99L...yet everyone is watching 99L..go figure
Member Since: August 6, 2011 Posts: 4 Comments: 33344

Viewing: 71 - 21

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 JeffMasters

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