Hailstorm Affects St. Kitts

What the hail? Residents of St. Kitts and Nevis had a bit more colorful language as hail fell out of the sky on Thursday morning, accompanying torrential rainfall that has produced street and flash flooding across the country.

According to the American Meteorological Society, a hailstorm is any storm that produces hailstones that fall to the ground, usually when the amount or size of the hail is considered significant. Stones between pea-sized (10 millimeters) to quarter-sized (20 millimeters), which is significant, were reported across several parts of St. Kitts.

What caused the severe weather?

A strong upper-level trough centered north of the Dominican Republic is chiefly responsible for Thursday’s severe weather. Combined with ample moisture and an induced surface to low-level trough, scattered strong thunderstorms affected much of the Leeward Islands on Thursday morning.

Thursday’s atmosphere had sufficient energy and instability available to develop showers and thunderstorms. Meteorologists measure this using CAPE or Convective Available Potential Energy. CAPE is the amount of fuel available to a developing thunderstorm.  More specifically, it describes the instability of the atmosphere and provides an approximation of updraft strength within a thunderstorm.  A higher value of CAPE means the atmosphere is more unstable and would therefore produce a stronger updraft. 

While this is just one part of the puzzle, several other factors (seen by the many, many indices on the right of the below graph) play a role in the development of a thunderstorm. On Thursday, the CAPE recorded at nearby Princess Juliana International Airport in Sint Maarten exceeded 1000. Though this is not exceptionally high, it was sufficient for strong but shallow thunderstorms.

The forecast remains unchanged for Friday as the hail threat shifts marginally westward towards Puerto Rico and western Dominican Republic.

The affected areas

Hail was primarily reported in Tabernacle, Saddlers Village, and Dieppe Bay, mainly across the northern portion of St. Kitts. The St. Kitts and Nevis Meteorological Service is assessing the reports and will update the public once their investigation has been concluded.

Power outages have also been reported at Phillips Village and Eco Park to Race Course Phase 1 Newtown Grounds.

A flash flood watch has been issued for low-lying and flood-prone areas of St. Kitts until 5:00 PM Thursday, April 6th, 2023. Weather stations across the island have recorded between 2 and 3.5 inches (50.8-88.9 mm) with an additional 1-2 inches forecast. Wind gusts up to 50 KM/H have also been recorded across both St. Kitts and Nevis.