Tropical Storm Arthur Strengthens, Tropical Storm Warnings In Effect for The Carolinas

At 5:00 PM, the National Hurricane Center continues to issue advisories on Tropical Storm Arthur, which continues to strengthen. This marks the 6th year in a row a tropical cyclone has formed before June 1st, the official start of the Hurricane Season.

At 5:00 PM AST, the center of Tropical Storm Arthur was located near latitude 31.5 North, longitude 77.2 West. Tropical Storm Arthur is moving toward the north-northeast near 15 KM/H. A turn toward the northeast with an increase in forward speed is expected during the next 24 to 36 hours. A turn toward the east is forecast to occur on Tuesday.

On the forecast track, Arthur will remain well offshore of the coasts of Georgia and South Carolina tonight, and then move near or just east of the coast of North Carolina on Monday. Arthur is forecast to turn away from the east coast of the United States Monday night and Tuesday.

Maximum sustained winds are near 45 MPH (75 KM/H) with higher gusts. Some gradual strengthening is forecast during the next day or so. Arthur is likely to lose tropical characteristics on Tuesday.

Tropical-storm-force winds extend outward up to 125 miles (205 KM) from the center. The estimated minimum central pressure is 1002 millibars (29.59 inches).

Tropical Storm Arthur Forecast Cone as of 5:00 PM Sunday 17th May 2020. Credit: National Hurricane Center

Watches & Warnings

Tropical Storm Arthur Watches and Warnings as of 5:00 PM Sunday 17tth May 2020. Credit: National Hurricane Center

A Tropical Storm Warning is in effect for:

  • Surf City to Duck NC
  • Pamlico and Albemarle Sounds

A Tropical Storm Warning means that tropical storm conditions are expected somewhere within the warning area, in this case within the next 24 hours.

Hazards Affecting Land

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

WIND: Tropical storm conditions are expected within the Tropical Storm Warning area on Monday.

RAINFALL: Arthur is expected to produce total rain accumulations of 1 to 3 inches (25 mm to 75 mm) over coastal North Carolina tonight and Monday, with locally higher amounts.

SURF: Swells generated by Arthur are affecting portions of the southeast U.S. coast and are expected to spread northward along the U.S. mid-Atlantic coast during the next day or two. These swells could cause life-threatening surf and rip current conditions.

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

Tropical Storm Arthur Forecast Discussion

Tropical Storm Arthur southeast of the Carolinas. Image: Weathernerds.org

Arthur’s satellite presentation has not changed much since the previous advisory. There are still some fragmented convective bands over the eastern portions of the circulation, but convective activity remains limited over the western half of the storm. A late-arriving ASCAT overpass from around the time of the previous advisory revealed somewhat lower wind speeds than reported by this morning’s reconnaissance aircraft. This could be the result of the convection becoming more fragmented after the aircraft sampled that portion of the storm or related to the low bias of the ASCAT instrument. Regardless, the initial intensity remains a possibly generous 40 kt for now. Another reconnaissance aircraft is scheduled to investigate Arthur this evening.

Arthur is forecast to remain within a low wind shear environment and over marginally warm sea surface temperatures through early Monday. These conditions favor some strengthening, however, the sprawling structure of the cyclone and nearby dry mid-level air are likely to temper any increase in wind speed. After 36-48 hours, baroclinic forcing is expected to help the post-tropical cyclone maintain its intensity. Later in the period, the frontal gradients decrease which should cause weakening.

Recent satellite fixes show that Arthur is still moving north-northeastward at about 8 knots (15 KM/H). The tropical storm should begin to accelerate northeastward overnight as a mid-level trough moves into the eastern United States. By Tuesday night, the steering flow is expected to become westerly which should cause Arthur to turn eastward, then southeastward later in the forecast period.

The lastest dynamical track guidance has come into a little better agreement through 36-48 hours with the GFS and ECMWF converging on the previous NHC track. As a result, little change was needed for the first couple of days of the earlier NHC track forecast. After that time, most of the guidance has trended toward a faster eastward and east-southeastward motion, and the NHC forecast has been adjusted accordingly in that direction as well.

Forecast Discussion by Forecaster Brown from the NHC.

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