Tag Archive for: Storm Prediction Center

Strong Thunderstorms, Street Flooding, Tornados Possible Tomorrow

Update: 10/28/22 11am: Today’s reports indicate the highest severe storm risk is shifting SW of Houston and offshore. Experts now predict 1-2 inches of rain for the Houston area today. Areas offshore are already getting 2-4 inches per hour.

Tomorrow will likely bring strong thunderstorms. Rainfall rates could exceed the capacity of street drains leading to localized street flooding. And the severe weather may also spin up some tornados, according to Harris County’s meteorologist and the National Weather Service (NWS).

Heavy Rainfall

NWS predicts two to three inches of rain could fall on Friday, as warm, moist air pushing in from the Gulf collides with a cold front pushing in from the northwest. Jeff Lindner, Harris County meteorologist, predicts the worst period for us will be Friday afternoon.

Tornados Possible

The NWS Storm Prediction Center in Norman, Oklahoma, issued this warning for Friday . It shows a marginal risk of severe weather for the entire Houston area and a slightly higher risk for areas south and west of us.

Reasons for Concern

For the weather wonks reading this, Lindner cites an unusual convergence of storm systems at different levels of the atmosphere.

A trough will begin to move eastward toward Texas later today. Surface pressures will begin to fall this afternoon as low pressure develops ahead of the approaching mid-level low. Southeast winds will increase today, letting Gulf moisture quickly return to coastal Texas.

As the mid-level low approaches us, it will meet the northward-moving, moisture-laden warm front moving in from the Gulf.

Severe threats will be highest along the boundary. Tropical moisture will march quickly northward tonight on a 30-knot low level jet. Precipitable waters – the amount of moisture in a column of air – will equal 1.8 inches by Friday morning over much of the region.

As large-scale lift increases over the developing warm sector, showers and thunderstorms will develop from southwest to northeast across the region.

The cold front associated with the mid-level low will sweep west to east across southeast Texas on Friday afternoon, touching off more thunderstorms. The front will slow Friday night, so showers will linger over the area.

Severe Threat: 

The surface low approaching from the northwest will meet the warm front coming from the opposite direction along a NW to SE axis on Friday. This warm front will extend from near San Antonio to near Freeport during the day and produce strong to severe thunderstorms. Low-level winds near the warm front will circle back toward the ESE and enhance low-level storm rotation.

Such collisions are notorious for tornado production, according to Lindner. Discrete cells may develop ahead of the line of storms approaching from the west. The location of the greatest severe risk will depend on where the warm front sets up Friday morning. Areas along and south of the front will have the highest risk.

If the warm front moves just a few miles farther north, it will increase risk to the Houston metro area. Kingwood was struck by tornados in a similar setup earlier this year.

Damaging winds will be the main threat. The worst of the storms should be over by 3-5 pm Friday, but lighter rains may linger well into the evening hours.  

Heavy Rainfall: 

Moisture will deepen Thursday into Friday. By Friday morning, a saturated air mass will be in place over the region. “Strong divergent lift coupled with low-level inflow will increase the potential for heavy rainfall along with cell training from southwest to northeast.”

Lindner describes himself as “aways wary of such setups.” They can help anchor and train convection.

The overall pattern favors supercell formation with both a tornado and heavy rainfall risk.

Jeff Lindner, Harris County Meteorologist

These storms could become significant rainfall producers – if they become sustained along the warm frontal boundary. The good news is that the ground is dry and can handle several inches of rainfall. “However, rainfall rates may exceed localized drainage capacities and result in some street flooding regardless of the dry ground conditions,” says Lindner.

Weekend: 

Cloudiness should linger much of Saturday keeping temperatures in the 50’s under northerly winds. South of the cloud line temperatures will warm into the 70’s. Where that line will be Saturday is hard to determine. Clouds should erode Saturday night with mostly clear skies. Sunday will be mild.  

Tropics:

The hurricane season has another month to go. It isn’t over yet! The National Hurricane Center now gives an area of low pressure moving WNW across the Caribbean a 50% chance of turning into a tropical depression in the next five days. No one is yet predicting what will happen if it does.

Posted by Bob Rehak on 10/27/22 based on information from Jeff Lindner, NWS, and NHC

1885 Days since Hurricane Harvey

Another Tropical Wave Headed Toward Gulf

By this weekend, the second tropical wave in two weeks will make its way into the Gulf of Mexico. The National Hurricane Center (NHC) is monitoring a disturbance in the southwestern Caribbean. They predict it will track northwest across Central America and the Yucatan. Then it should emerge into the Gulf of Mexico later this week.

It’s too early to tell the exact track, timing or degree of development. That depends on many factors such as steering currents and frontal boundaries. But as of 7am Houston time on 8/16/22, NHC gives the disturbance a 20% chance of developing into a named storm within 5 days.

NHC says an area of low pressure could form on Friday. Gradual development of this system is possible while it moves northwestward over the southwestern Gulf of Mexico through the weekend.

15:20 Zulu time is 10:20 Houston time. Note the cloud formation in lower left over Nicaragua and Honduras.

Harris County Meteorologist Jeff Lindner says conditions will become increasing favorable for tropical cyclone development in the Bay of Campeche (the area with the yellow circle). He points to a frontal boundary dropping south toward the Texas coast late this week and says areas south of that boundary will become increasingly favorable for a low pressure system to develop along the axis of the tropical wave.

Weather Service Storm Prediction Center 3-Day Outlook shows front moving across southern plains on Friday.

However, there’s no reason to panic now. Just watch the National Hurricane Center website closely over the next several days for any changes.

Almost exactly 5 years ago, a storm followed a similar track across the Yucatan. It eventually became known as Hurricane Harvey.

Posted by Bob Rehak on 8/16/2022

1813 Days since Hurricane Harvey