Tropical Storm Beta Continues To Organize In The Gulf of Mexico

Tropical Depression Twenty-Two was upgraded to Tropical Storm Beta on Friday, as it meanders in the western Gulf of Mexico. Beta is forecast to become a hurricane over the weekend into next week, prompting storm surge and hurricane watches for parts of the U.S. Gulf Coast.

This is the 22nd tropical cyclone of the 2020 Atlantic Hurricane Season and the earliest 23rd named storm, beating Tropical Storm Alpha of 2005 by 34 days.

This discrepancy (since Beta should be the earliest 24th named storm) is due to an unnamed tropical cyclone forming on October 4th, 2005 between Stan and Tammy during the 2005 Atlantic Hurricane Season.

List of names for the 2020 Atlantic Hurricane Season. The next named tropical cyclone will be called Gamma.
List of names for the 2020 Atlantic Hurricane Season. The next named tropical cyclone will be called Gamma.

At 11:00 PM AST, the center of Tropical Storm Beta was located near latitude 25.5 North, longitude 92.3 West. Beta is moving toward the north-northeast near 12 mph (19 km/h). A slow westward motion is expected to begin late Saturday, with a slow northwestward motion forecast to begin late Sunday and continue through late Monday. On the forecast track, the center of Beta will slowly approach the Texas coast into early next week.

Data from the Air Force Hurricane Hunter aircraft indicate that maximum sustained winds have increased to near 60 mph (95 km/h) with higher gusts. Additional strengthening is forecast, and Beta is expected to become a hurricane on Sunday.

Tropical-storm-force winds extend outward up to 175 miles (280 km) from the center. The estimated minimum central pressure is 996 millibars.

Tropical Storm Beta Forecast Track as of 11:00 PM AST Friday 18th September 2020. (National Hurricane Center)
Tropical Storm Beta Forecast Track as of 11:00 PM AST Friday 18th September 2020. (National Hurricane Center)

Watches & Warnings

Tropical Storm Beta Watches and Warnings as of 11:00 PM AST Friday 18th September 2020. (National Hurricane Center)
Tropical Storm Beta Watches and Warnings as of 11:00 PM AST Friday 18th September 2020. (National Hurricane Center)

A Storm Surge Watch is in effect for:

  • Port Mansfield, TX to High Island, TX including Baffin Bay, Corpus
    Christi Bay, Copano Bay, Aransas Bay, San Antonio Bay, Matagorda
    Bay, and Galveston Bay

A Hurricane Watch is in effect for:

  • Port Aransas Texas to High Island Texas

A Tropical Storm Watch is in effect for:

  • South of Port Aransas Texas to the Mouth of the Rio Grande
  • East of High Island Texas to Morgan City Louisiana

A Storm Surge Watch means there is a possibility of life-threatening inundation, from rising water moving inland from the coastline, in the indicated locations during the next 48 hours. For a depiction of areas at risk, please see the National Weather Service Storm Surge Watch/Warning Graphic, available at hurricanes.gov.

A Hurricane Watch means that hurricane conditions are possible within the watch area. A watch is typically issued 48 hours before the anticipated first occurrence of tropical-storm-force winds, conditions that make outside preparations difficult or dangerous.

A Tropical Storm Watch means that tropical storm conditions are possible within the watch area, generally within 48 hours.

For storm information specific to your area, including possible inland watches and warnings, please monitor products issued by your local National Weather Service forecast office.

Hazards Affecting Land

Tropical Storm Beta probabilities for tropical-storm-force winds as of 11:00 PM AST Friday 18th September 2020, as well as the most likely time of arrival of tropical-storm-force winds. (National Hurricane Center)
Tropical Storm Beta probabilities for tropical-storm-force winds as of 11:00 PM AST Friday 18th September 2020, as well as the most likely time of arrival of tropical-storm-force winds. (National Hurricane Center)

WIND: Hurricane conditions are possible within the hurricane watch area by late Monday or Monday night, with tropical storm conditions possible by late Sunday. Tropical storm conditions are possible within the tropical storm watch area along the upper Texas and southwestern Louisiana coast as early as late Saturday. Tropical storm conditions are possible within the tropical storm watch area along the south Texas coast late Sunday.

Tropical Storm Beta Peak Storm Surge Forecast as of 11:00 PM AST Friday 18th September 2020. (National Hurricane Center)
Tropical Storm Beta Peak Storm Surge Forecast as of 11:00 PM AST Friday 18th September 2020. (National Hurricane Center)

STORM SURGE: The combination of a dangerous storm surge and the tide will cause normally dry areas near the coast to be flooded by rising waters moving inland from the shoreline. The water could reach the following heights above ground somewhere in the indicated areas if the peak surge occurs at the time of high tide:

  • Port Mansfield, TX to High Island, TX including Baffin Bay, Corpus Christi Bay, Copano Bay, Aransas Bay, San Antonio Bay, Matagorda Bay, and Galveston Bay: 2-4 ft
  • Mouth of the Rio Grande to Port Mansfield, TX: 1-3 ft
  • High Island, TX to Morgan City, LA including Sabine Lake, Calcasieu Lake, and Vermilion Bay: 1-3 ft

The deepest water will occur along the immediate coast in areas of onshore winds, where the surge will be accompanied by large and destructive waves. Surge-related flooding depends on the relative timing of the surge and the tidal cycle and can vary greatly over short distances. For information specific to your area, please see products issued by your local National Weather Service forecast office.

RAINFALL: There is an increasing risk of heavy rainfall and flooding along the northwest Gulf Coast Sunday through at least the middle of next week as Beta is forecast to move slowly toward and along or offshore of the coast through that time. For additional information, see products from your local National Weather Service office.

SURF: Swells are expected to increase and reach the coast of Texas and the Gulf Coast of Mexico over the weekend, generated by a combination of Beta and a cold front entering the northern Gulf of Mexico. These swells are likely to cause life-threatening surf and rip current conditions. Please consult products from your local weather office.

This system is of no direct threat to the Windward Islands, including Trinidad and Tobago.

Tropical Storm Beta Forecast Discussion

Tropical Storm Beta in the Western Gulf of Mexico (Weathernerds)
Tropical Storm Beta in the Western Gulf of Mexico (Weathernerds)

An Air Force Reserve Hurricane Hunter aircraft investigating Beta this evening found that the center has re-formed or been tugged northeastward by bursts of strong convection. While flying through that convection, the plane measured a peak flight-level wind of 57 kt at 10,000 feet before descending to 2500 feet. To the northwest of the center, the SFMR instrument on the plane measured a solid area of 46-48 kt, and there have been multiple ship reports in the region of 40-45 kt. Based on all these data, Beta’s initial intensity is estimated to be 50 kt. The plane reported an extrapolated minimum pressure of 996 mb on the last pass through the center, which also corresponds to a typical 50-kt tropical storm.

The aircraft fixes indicate that Beta is moving north-northeastward, or 030/10 kt. This motion is expected to continue for the next 12 hours or so, but as mid-level ridging develops over the Southern Plains on Saturday, Beta should begin to slow down and turn westward. A slow motion in the direction of the Texas coast should continue through day 3, with a shortwave trough possibly causing the cyclone to recurve and move northeastward near or along the Texas coast on days 4 and 5. While there remains a large amount of spread among the track models, they all agree on this general scenario and indicate that Beta is likely to move very slowly as it makes its closest approach to the Texas coast. The initial position fixed by the plane necessitated a northward shift in the NHC official forecast compared to the previous forecast for the first 3 days, but it comes back in line with the previous prediction on days 4 and 5.

Beta has been able to strengthen despite being affected by strong southwesterly shear. The shear could begin to relax over the next few days, particularly by day 2 and 3, which could allow for some further strengthening. The SHIPS guidance remains the most aggressive of the intensity models, and the NHC intensity forecast leans heavily toward those solutions given Beta’s recent intensification trend (which SHIPS seemed to handle better). Beta is forecast to steadily strengthen and become a hurricane in a couple of days as it approaches the Texas coast. Some weakening is forecast on days 4 and 5 due to another increase in southwesterly shear and possible land interaction.

Tropical Storm Beta Key Messages (National Hurricane Center)
Tropical Storm Beta Key Messages (National Hurricane Center)

Key Messages:

  1. There is an increasing risk of heavy rainfall and flooding along the northwest Gulf Coast Sunday through at least the middle of next week as Beta is forecast to move slowly toward and along or offshore of the coast through that time. For additional information, see products from your local National Weather Service office.
  2. Life-threatening storm surge and hurricane-force winds are possible along portions of the Texas coast early next week, with tropical storm conditions possible by late this weekend. Storm Surge and Hurricane watches are in effect, and residents in these areas should ensure they have their hurricane plan in place and follow advice given by local officials.

Forecast Discussion by Forecaster Berg from the NHC.

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