Wind Shear Rips into Tropical Storm Harvey

Located about 125 miles north-northeast of Curacao at 11 am EDT Saturday, Harvey was racing westward at 22 mph. Harvey’s envelope of convection (showers and thunderstorms) had become much more fragmented and elongated, a byproduct of the storm’s rapid motion coupled with persistently strong wind shear of 20-25 knots. It is possible Harvey will be stretched to the point where it loses its closed surface circulation and becomes an open wave by late Saturday. Assuming Harvey survives till Sunday, it will be moving into the western Caribbean, where wind shear is predicted by the 12Z Saturday SHIPS model to drop to the 5-10 knot range. Mid-level relative humidity should increase from around 50% to greater than 70%. This will give Harvey a much more supportive environment for strengthening. Sea-surface temperatures will remain quite warm along Harvey’s path, around 29°C (84°F)—roughly 0.5°C above average. These warm waters are quite deep, providing ample oceanic heat content to enhance strengthening if Harvey does remain a tropical cyclone.