Cloud Stalker: TROPICAL STORM ARTHUR

Monday, May 18, 2020

TROPICAL STORM ARTHUR

...TROPICAL STORM ARTHUR...

Tropical Storm Arthur is near 33.5N 76.6W at 18/0900 UTC, or 
about 75 nm S of Morehead City, North Carolina, moving NNE at 12 
kt. Minimum central pressure is 1002 mb and maximum sustained 
winds are near 40 kt with gusts to 50 kt. Scattered moderate to 
isolated strong convection is from 33N to 37N W of 72W.

On the forecast track, the center of Arthur will approach the 
coast of North Carolina during the next few hours, and then move 
near or just east of the coast of North Carolina later today. 
Arthur is then forecast to turn away from the east coast of the 
United States tonight and Tuesday. While some strengthening is 
forecast during the next 48 hours, Arthur is likely to lose its 
tropical characteristics on Tuesday.Ramos

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HAIL (3/4 inch or greater)

Hail can cause significant damage to your vehicle, break windows and damage roofs of homes and businesses.
Hail can cause significant bodily injuries such as broken bones and even blindness if wind blown.
Softball (4.5 inches) sized hail was reported in Lake Wales, Florida on March 30, 1996.
Haildrifts, up to four feet deep of dime to nickel sized hail, occurred in low-lying areas near Zephyrhills, Florida on January 29, 1997.
Hailstones the size of softballs can fall at speeds faster than 100 mph

supercell

Supercells derive their rotation through tilting of horizontal vorticity (an invisible horizontal vortex) caused by wind shear. Strong updrafts lift the air turning about a horizontal axis and cause this air to turn about a vertical axis. This forms the deep rotating updraft, the mesocyclone.
A cap or capping inversion is usually required to form a downdraft of sufficient strength. The cap puts an inverted (warm-above-cold) layer above a normal (cold-above-warm) boundary layer, and by preventing warm surface air from sinking too far, allows one or both of the following:
Air below the cap warms and/or becomes more moist
Air above the cap cools
This creates a warmer, moister layer below a cooler layer, which is increasingly unstable (because warm air is less dense and tends to rise). When the cap weakens or moves, explosive development follows.
In North America, supercells usually show up on Doppler radar as starting at a point or hook shape on the southwestern side, fanning out to the northeast. The heaviest precipitation is usually on the southwest side, ending abruptly short of the rain-free updraft base or main updraft (not visible to radar). The rear flank downdraft, or RFD, carries precipitation counterclockwise around the north and northwest side of the updraft base, producing a "hook echo" that indicates the presence of a mesocyclone.