Tropical Storm Nicholas Forms in Gulf

A USAF mission this morning found low-level circulation and a large area of 40-50mph winds over the western Gulf. Additionally, satellite images show an expansion of the scattered deep convection associated with the system. Based on this, the system has been upgraded to Tropical Storm Nicholas. The storm is moving NNW at 13mph and this motion is expected to continue today.

  • Tropical Storm Warnings have been issued from the Mouth of the Rio Grande to Port Aransas TX
  • Tropical Storm Watches have been issued from Port Aransas TX to High Island TX including Matagorda and Galveston Bays.
  • Storm surge watch has been issued from the mouth of the Rio Grande to High Island TX
  • Flash Flood Watch from 7PM tonight through Tuesday night for most of Houston region
NOAA satellite image of Nicholas as of 10AM CDT Houston time.
Nicholas’ track should bring the storm onshore near Matagorda Bay.

Jeff Lindner, Harris County Meteorologist, predicts, “Nicholas will be moving over warm waters of the western Gulf of Mexico in fairly favorable upper level conditions and steady intensification is likely up to landfall. Most models predict the system to become a mid-range tropical storm. The National Hurricane Center forecasts a 65mph tropical storm at landfall. A reasonable worst case potential is a category 1 hurricane, but at this time that looks unlikely.

Nicholas’ track places southeast Texas on the “dirty” side of the system with onshore winds and bands of heavy rainfall,” says Lindner.

Rainfall Starting Later Today

By late today, heavy rain is expected to reach portions of the Texas and Louisiana coasts, with a heavy rain threat continuing across coastal areas through the middle of the week. Localized significant rainfall could produce areas of flash, urban, and isolated river flooding.

Hourly rainfall rates could be high during this time with 2-3 inches possible, which would lead to some flooding in more urban areas. 

How far this storm moves inland will determine how far heavy rains advance on Monday. Says Lindner, “Certainly the coastal counties (Chambers, Galveston, Brazoria, Matagorda, and Jackson) will see heavy rainfall, but this could extend inland into southern Liberty, southern Harris, Fort Bend, and Wharton counties also.” He predicts:

  • Coastal Counties: widespread 5-8 inches (isolated areas 10-15 inches)
  • South of I-10: widespread 3-6 inches (isolated areas 8-12 inches)
  • North of I-10: widespread 2-4 inches (isolated areas 6 inches)
5-Day Forecasted Accumulated Rainfall
The NWS Weather Prediction Center shows heavy rain and flash flooding are possible for most of the upper Texas coast through mid-week.

Flood Potential

Lindner says, “Given the tropical moisture in place hourly rainfall rates of 2-4 inches will be possible under the stronger cells which will lead to quick accumulations. While grounds are dry initially, waves of rainfall will gradually saturate the soils leading the increasing run-off. Flooding will be possible, especially across the coastal counties and areas south of I-10 where the greatest rainfall is most likely at the moment.”

Most of the Houston area will have a slight (10%) chance of flash flooding for the next three days.

Tropical-Storm-Force Winds Should Arrive in Houston Tuesday Morning

Tropical storm force winds should hit the Houston area Tuesday morning.

2-4 Feet of Storm Surge Likely in Galveston Bay

Nicholas should bring 2-4 feet of storm surge to the upper Texas coast.

Posted on 9/12/2021 by Bob Rehak based on Information from NHC and HCFCD

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