Tropical Storm Chantal (2007) - Meteorological History

Meteorological History

A frontal system moved off the Carolinas on July 21, and as it drifted southeastward it degenerated into a trough of low pressure; by July 26, it was nearly stationary to the east of the Bahamas. Deep convection initially failed to persist, though on July 28 meteorologists began tracking it with the Dvorak technique. The system tracked northeastward, and initially unfavorable environmental conditions left the system disorganized. However, conditions were forecast to become more conducive for development, and by July 29 the National Hurricane Center remarked it had "potential for tropical or subtropical development." On July 30, the low passed to the west of Bermuda as it continued northeastward, under the influence of a large mid-latitude trough. The system contained an exposed low-level circulation, which intermittently passed beneath a persistent area of convection to its northeast. By early on July 31, ship reports and QuikSCAT observations suggested winds of 35 mph (55 km/h), and the center was well-involved enough with the convection for the National Hurricane Center to classify it as Tropical Depression Three while it was located about 270 miles (435 km) north-northwest of Bermuda, or about 445 miles (710 km) south-southeast of Chatham, Massachusetts.

Upon receiving its classification, the depression consisted of a partially exposed low-level center with deep convection occupying the northeastern semicircle. Located over sea surface temperatures of about 80 °F (27 °C), one forecaster noted the depression had "a small window of opportunity... for it to reach tropical storm strength before transitioning to an extratropical cyclone." Convection increased further over the center, and at around 0600 UTC on July 31 the depression intensified into Tropical Storm Chantal while located about 530 miles (855 km) south of Halifax, Nova Scotia. The storm continued northeastward, under the influence of a mid-level trough, and Chantal quickly developed well-defined curved banding features; six hours after becoming a tropical storm, Chantal reached peak winds of 50 mph (85 km/h). The storm tracked through an area of progressively cold waters and cooler air, resulting in the weakening of its convection. The circulation became embedded within the approaching frontal zone, and by 0600 UTC on August 1 Chantal transitioned into an extratropical cyclone.

After becoming an extratropical cyclone, Chantal maintained scattered convection near its center, though its main area of convection and clouds extended to its north. Midday on August 1, the cyclone struck Newfoundland along the Avalon Peninsula, hitting the Placentia Area with full force. It subsequently intensified to attain winds of near hurricane-force. On August 3 the cyclone underwent a final weakening trend in the far northern Atlantic Ocean, and on August 5 the extratropical remnants of Chantal merged with another extratropical cyclone to the east of Iceland.