Tropical Storm Bertha Quickly Forms, Making Landfall Across South Carolina

On Tuesday evening, the National Hurricane Center was monitoring a tropical disturbance, INVEST 91L, off the coast of Florida with low chances of development. 12 hours later, the NHC began issuing advisories on Tropical Storm Bertha, which rapidly organized overnight. As quickly as it formed, it made landfall this morning near Mount Pleasant, South Carolina as a tropical storm.

The last time two named stormed formed in May was in 2012. The only years on record (since 1851) with 2 Atlantic named storms prior to May 27 are 1887, 1908, 1951, and 2012. This is the fourth Atlantic storm named Bertha to make continental US landfall. Other 3 were: Tropical Storm Bertha (1957) in TX, Category 2 Hurricane Bertha (1996) in North Carolina, and Tropical Storm Bertha (2002) in Louisiana.

At 11:00 AM AST, the center of Tropical Storm Bertha was located near latitude 33.3 North, longitude 79.5 West. Tropical Storm Bertha is
moving toward the north near 15 MPH (24 KM/H) and this general motion is expected to continue through tonight with a gradual increase in forward speed.

On the forecast track, Bertha will move inland across eastern and Northern South Carolina later today and into central North Carolina by tonight.

Maximum sustained winds are near 50 MPH (85 KM/H) with higher gusts. Weakening is forecast during the next 48 hours. Tropical Storm Bertha is expected to weaken to a tropical depression later today and become a remnant low tonight.

Tropical-storm-force winds extend outward up to 25 miles (35 KM) from the center. The estimated minimum central pressure is 1005 millibars.

Tropical Storm Bertha Forecast Cone as of 11:00 AM Wednesday 27th May 2020. Credit: National Hurricane Center
Tropical Storm Bertha Forecast Cone as of 11:00 AM Wednesday 27th May 2020. Credit: National Hurricane Center

Watches & Warnings

Tropical Storm Bertha Warnings as of 11:00 AM Wednesday 27th May 2020. Credit: National Hurricane Center
Tropical Storm Bertha Warnings as of 11:00 AM Wednesday 27th May 2020. Credit: National Hurricane Center

A Tropical Storm Warning is in effect for:

  • Edisto Beach SC to South Santee River SC

A Tropical Storm Warning means that tropical storm conditions are expected somewhere within the warning, in this case for the next few hours.

Hazards Affecting Land

Tropical Storm Bertha's Key Messages. Credit: National Hurricane Center
Tropical Storm Bertha’s Key Messages. Credit: National Hurricane Center

WIND: Tropical storm conditions are expected to continue near the coast for the next few hours.

Tropical Storm Bertha Excessive Rainfall Outlook as of 9:56 AM Wednesday 27th May 2020. Credit: National Hurricane Center
Tropical Storm Bertha Excessive Rainfall Outlook as of 9:56 AM Wednesday 27th May 2020. Credit: National Hurricane Center

RAINFALL: Bertha is expected to produce total rain accumulation of 2 to 4 inches with isolated totals of 8 inches across eastern and central South Carolina into west-central to far southeastern North Carolina and southwest Virginia. Given very saturated antecedent conditions, this rainfall may produce life-threatening flash flooding, aggravate and prolong ongoing river flooding, and produce rapid out of bank rises on smaller rivers.

Tropical Storm Bertha Rainfall Accumulation as of 9:56 AM Wednesday 27th May 2020. Credit: National Hurricane Center
Tropical Storm Bertha Rainfall Accumulation as of 9:56 AM Wednesday 27th May 2020. Credit: National Hurricane Center

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

Tropical Storm Bertha Forecast Discussion

Tropical Storm Bertha moving across the Carolinas. Image: Weathernerds.org

The circulation of Bertha remained compact yet well-defined through landfall, which occurred around 930 AM EDT near Mount Pleasant, South Carolina. Buoy data around that time indicated that maximum sustained winds had increased to around 45 kt.

Although the center has moved inland, a strong rain band with onshore flow continues to slowly migrate northward along the South Carolina coast. Therefore it is anticipated that tropical-storm-force winds will remain possible in the warning area over the next few hours. Bertha is expected to weaken to a tropical depression later today, then weaken to a remnant low tonight as the center moves farther inland.

Model guidance is in good agreement on taking the weakening cyclone north to north-northwestward through tonight, followed by a turn to the north-northeast along with an increase in forward speed later on Thursday. This official track is only slightly east of the previous one and is near the multi-model consensus.

Forecast Discussion by Forecaster Latto/Beven from the NHC.

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