Tag Archive for: 99L

Chances of Tropical Formation for 99L Increase to 80%

As of 7 pm CDT on 8/19/22, the National Hurricane Center (NHC) gave a tropical disturbance in the Gulf an 80% chance of turning into a named storm today or tomorrow. They call this area of investigation “99L.” Two days ago, the NHC gave this only a 10% chance of developing. But it survived going over the rugged terrain of Central America and is now out over water again where conditions are favorable for development.

From National Hurricane Center

Satellite imagery indicates that showers and thunderstorms are getting better organized. Deep thunderstorms have developed near/over this low pressure center.

Satellite photo taken at noon Houston time on 8/18/22.

According to NHC, environmental conditions appear favorable for additional development, and a tropical depression could form as the system moves northwestward across the southwestern and western Gulf of Mexico as early as today. However, by Saturday night, NHC predicts the system will move inland over northeastern Mexico, which will end its chances of development.

Conditions that support continued development include light wind shear, a large plume of moisture and very warm sea surface temperatures.

Jeff Lindner, Harris County Meteorologist

Interests along the lower Texas coast should monitor the progress of this system. Regardless of development, this system could bring locally heavy rains to southern Texas over the weekend.

More Rain for Houston Expected

In the northern hemisphere, low-pressure systems like this one rotate counterclockwise. So as the system heads toward Brownsville, it will spin moisture up along the Texas Gulf coast. That’s part of the reason why our rain chances for the next few days will remain high.

From Weather Live as of 12:40pm, 8/18/22.

As moisture from 99L spreads northward, it will interact with an incoming frontal boundary from the north and northwest early next week. That will also enhance rainfall chances.

Areas where Precipitable Water in atmosphere exceeds 1.5″. Precipitable waters are defined as the amount of water vapor in a column of air. Source: NWS Storm Prediction Center.

The National Weather Service’s Weather Prediction Center calls for another 4-5 inches of rain during the next 7 days.

Expected rainfall totals through 8/27/2022

Evening Update

As of 6:34 pm Houston time, NHC has increased the chances of formation to 80% and has started referring to the storm in the Gulf as “potential tropical cyclone #4.” Hurricane Hunter aircraft this afternoon did not find closed circulation. The plane did find an area of 25-30kt winds well to the northeast of the weak wind field near the active thunderstorms. The system is morning NW at around 15mph. Lindner expects the storm to make landfall as a 45 mph tropical storm tomorrow evening near the Rio Grande.

For more information, including the expected arrival time of tropical storm force winds, warning cones, and wind-speed probabilities, click here.

Conditions are changing rapidly. For the latest updates, monitor the National Hurricane Center website. During hurricane season, I bookmark this page and have it readily available on my phone.

Posted by Bob Rehak on 8/18/2022

1816 Days since Hurricane Harvey

So Far, 99L Headed Toward Gulf Along Same Track as Harvey

Jeff Lindner, Harris County’s meteorologist, forecasts a potential hurricane threat for the western and northwestern Gulf of Mexico early next week. And it’s following the same track as Harvey – almost four years later to the day.

Current Location of 99L in South-Central Caribbean

A tropical wave currently designated 99L and moving westward in the Caribbean off the coast of Columbia still has no center of circulation. However, global models indicate that it will continue to develop over the western Caribbean Sea either Friday or Saturday and move into the south-central Gulf of Mexico over the weekend.

Area of Investigation 99L is that large blob between the eastern tip of Cuba and the northern coast of Colombia.
99L on left should reach the southern Gulf by this weekend.

Still a Wide Range of Potential Tracks for 99L

There has been a significant shift during the last 24 hours to the right (east). The majority of the models now show 99L heading in the direction of the northwest Gulf of Mexico. However, models also show a wide range of potential tracks from northern Mexico to the Mississippi coast. 

The black line is the most likely track but uncertainty remains high.

So, a fair amount of uncertainty exists in the forecast, especially since there is such spread in the ensemble guidance. The lack of a defined surface center at the moment increases that uncertainty. 

Hurricane Harvey’s track in 2017. Note the similarity in area of origin and projected paths. Also note where Harvey intensified.

This weekend will be the fourth anniversary of Harvey. It’s eerie to note the similarities between that storm and this one.

Intensification Very Likely

Conditions over the Gulf of Mexico appear to be favorable for intensification. 

Nearly all global models see 99L turning into a hurricane. Some see it turning into an intense hurricane in the Gulf by early next week.

Lindner warns that It is too early to start discussing impacts because of the uncertainty on the track. However, he does see increasing tides and 10-15 foot waves from Sunday into Monday. Rain chances will increase starting today and remain high into the weekend. 

“Obviously,” says Lindner, “the forecast and potential impacts will have significant changes as the track become more clear in the coming days.”

Residents and interest along the TX and LA coast should review hurricane plans and make sure hurricane supplies are fully stocked. Monitor forecasts closely and frequently.

Posted by Bob Rehak on 8/25/2021 based on information from HCFCD, NOAA, NHC and Tropical Tidbits

1457 Days since Hurricane Harvey

Conditions in Atlantic Becoming More Favorable for Tropical Development

I just received an email from Jeff Lindner, Director of Hydrologic Operations Division/Meteorologist for Harris County Flood Control District about a potential tropical development.

Linder says, “There has been little mention of the Atlantic tropics thus far this hurricane season…even though we are already on our “E” storm. Most of the storms have been focused in the sub-tropical north Atlantic away from the generally hostile conditions in the deep tropics and far removed from any land interaction.”

National Hurricane Center Five Day Graphical Tropical Weather Outlook gives this tropical disturbance a 20% chance of tropical formation over the next five days.

Conditions in Tropics Becoming More Favorable for Tropical Development

“However conditions are starting to slowly change and as is usual for mid-August, conditions are becoming more favorable for tropical development in the deep tropics or that region between Africa and the Caribbean Sea,” said Lindner.

Tropical Wave 99L

Lindner continued: “A tropical wave roughly 850 miles east of the southern Windward Islands has shown an increase in deep convection today. This convection (thunderstorms) remains fairly disorganized at this time. Significant amounts of Saharan Air (dusty air from the deserts of N Africa) have been generally keeping the formation of convection to a minimum for the last 2 months, but 99L has found itself far to the south (near 8N) and mainly south of the dusty air across the mid Atlantic. This system has also found itself near/under a building ridge of high pressure aloft and removed from the anomalous strong wind shear thus far this year across the Caribbean Sea and Atlantic.”

“Conditions appear at least marginally favorable for some slow development of this feature as it moves W to WNW over the next 48-72 hours.”

“There is little to no model support for this feature to develop, but we shall see what the 00Z and 12Z models suggest. At the 800pm this evening, the Hurricane Center is giving this system a 20% chance of tropical development over the next 5 days as it moves generally toward the eastern Caribbean Sea.”

Lindner Cautions Against Looking Too Far into Future

“Reminder: it is important as we move into the heart of hurricane season to get information from trusted sources – especially on social media. Posts showing where a storm could be 7-9 days from now and at some level of intensity should not be believed and it is important to refrain from sharing such posts without proper context,” cautioned Lindner.

Peak of Hurricane Season is September 10

The statistical peak of hurricane season for this area is September 10, so we are still almost a month away. Nevertheless, be prepared. Check your your hurricane kit now. Don’t leave important matters for the last minute.

SJRA Still Lowering Lake Conroe

The San Jacinto River Authority (SJRA) has been steadily lowering Lake Conroe by 275 cubic feet per second to create extra capacity in the lake.  From a normal level of 201 mean feet above sea level (MSL), the goal was to reduce the lake to 199 MSL by August 15 and maintain that level until the end of September. This is to create an additional buffer against downstream flooding until the Army Corps can restore the carrying capacity of the West Fork.

However, recent rains have been refilling the lake almost as fast as the SJRA is lowering it. At the time of this post, the level was at 200.01 MSL. Visit SJRA.net to see the current level and release rate.

I am sure they will increase the discharge rate if this or any other storm approaches to get to their target of 199 MSL.

In short, nothing to worry about now. But keep your antenna up.

Posted by Bob Rehak on August 15, 2018

351 Days since Hurricane Harvey.