Tropical Storm Isaias Update 04 August

  POSTED ON: Tuesday, August 4, 2020 6:30 AM by Meteorologist A.R. Davies

BLUF:

Tropical Storm Isaias made landfall as a Hurricane near Ocean Isle Beach, NC at 2310 last night. Since then, the storm has weakened and rapidly moved northward. Tropical Storm Isaias is currently located near Roanoke Rapids, NC with maximum winds of 70 mph. The center of Isaias is still expected to pass near or just east of Annapolis on Tuesday. Impacts will be felt in Annapolis, including possible tropical storm force sustained winds (>39 mph), and more likely wind gusts as high as 65 mph with heavy rainfall that could lead to localized freshwater flooding. There is also a chance for minor or moderate coastal flooding throughout the day. The heaviest rain and strongest wind gusts will likely occur between 0900 EDT and 1400. The National Weather Service has issued a Tropical Storm Warning, a Flash Flooding Watch until 2300, a Tornado Watch until 1200, and a Coastal Flood Warning from 1100 today through 0300 on 05 August. 

DETAILS: 

Hurricane Isaias made landfall at 2310 on 03 August near Ocean Isle Beach, NC with maximum sustained winds of 85 mph. Nearby weather stations in North Carolina at Oak Island, Wrightsville Beach, Wilmington, and New River Marine Corps Air Station reported wind gusts overnight of 85 mph, 84 mph, 74 mph, and 63 mph, respectively. The storm has quickly accelerated north-northeast and has lost some strength. As of the 0500 update from the National Weather Service (NWS) National Hurricane Center (NHC), the center of Tropical Storm Isaias is located 15 miles southeast of Roanoke Rapids, NC and 85 miles west-southwest of Norfolk, VA. Isaias has been downgraded to a Tropical Storm with maximum sustained winds of 70 mph, and is moving north-northeast at 28 mph. The center of Isaias will be crossing into Southern Virginia by 0700, which is sooner than forecasted yesterday.

The storm track for Tropical Storm Isaias held firm overnight. The center of Isaias is still expected to pass just south and east of Annapolis late this morning-- although it could be a near miss with what is left of the eye wall potentially passing over the City. Tropical storm force sustained winds are possible between 0900 and 1300, with wind gusts as high as 65 mph during that time. For this reason, the NWS has issued a Tropical Storm Warning.

The heaviest rainfall is expected to arrive between 0800 and 0900, with rainfall rates over one inch per hour possible between 0900 and 1300. Widespread rainfall totals between 4.0 and 6.0 inches are expected throughout the Baltimore-Washington-Annapolis metro region, with isolated totals up to 7.0 inches. A Flash Flood Watch is in effect until 2300 today.  As with all landfalling tropical systems, isolated tornadoes are possible and can occur with little warning. Therefore a Tornado Watch is in effect until 1200. 

The threat for coastal flooding remains uncertain and complex. The maximum water levels during the high tide this morning at 0642 are now expected to only reach 2.0 to 2.5 ft above MLLW, which is below minor flood stage. The next high tide will occur today at 2037 and, depending on the storm track through Maryland, minor or moderate coastal flooding is possible during this high tide and during the tidal cycle leading up to it. Maximum water levels between 2.7 and 3.7 ft above MLLW are possible today. Due to the uncertainty in the water levels and threat of moderate flooding, a Coastal Flood Warning is in effect from 1100 today through 0300 on 05 August.

Power outages will be a significant concern with this system due to the combined threat of prolonged periods of heavy rainfall and gusty winds (which will also be variable in direction). The two primary services provided for the Baltimore-Washington-Annapolis metro region are Pepco and BGE. Both released statements yesterday that they are anticipating outages and increasing operations in the event of power disruption. As a point of reference, I’ve been up since 0500 and already the power has flickered a few times at my house in South Bel Air, MD. The BGE power outage map is available here: https://www.bge.com/Outages/CheckOutageStatus/Pages/OutageMap.aspx. The Pepco power outage map is available here: https://www.pepco.com/Outages/CheckOutageStatus/Pages/ViewOutageMap.aspx.

ISSUED: 04 August 2020 at 0625 EDT
FORECASTERS: Meteorologist A.R. Davies

Category: General Interest