Wednesday, October 7, 2009

Tropical Storm Henri (2009)

Storm Active: October 6-8

Near the end of September, a tropical wave emerged off the coast of Africa and moved westward. By October 1, the system already was associated with a large area of showers and thunderstorms. The deep tropical moisture enriched the system and contributed to its organization, but it did not develop a well-defined center. The wave moved northwest, out of favorable conditions, but convection persisted. Then, on October 6, a rapid intensification occurred, and the system was declared Tropical Storm Henri. Henri's convection was displaced to the east of the center by El Nino-related west to east sheer, much like Danny and Erika before it. Despite these adverse conditions, Henri gained strength, reaching its peak intensity of 50 mph winds and a pressure of 1005 millibars. Henri paralleled the northern islands of the Caribbean Sea to their north, causing raised surf. Henri weakened later on October 7, and, overnight, became a tropical depression. By the early evening of October 8, Henri had disintegrated into almost nothing on satellite imagery, and it decayed into a remnant low. The low quickly dissipated on October 9. No significant effects resulted from this system.

Henri at peak intensity north of the Caribbean Sea.

Track of Henri.

Tuesday, October 6, 2009

Tropical Storm Grace (2009)

Storm Active: October 4-5

On October 1, the center of a non-tropical low over the Azores developed a small area of showers. However, the showers didn't persist and no tropical cyclone formed. The low moved slowly northeast, hindered by a stationary front to its north into October 4. Then, an area of convection flared up rapidly within the low that evening, resulting in it being classified as Tropical Storm Grace. It formed at 41.2 N and 20.3 W, making it the farthest northeast a tropical cyclone has ever formed on record, Since the low was already fairly strong (995 millibars before Grace's formation) Grace already had reached a strong tropical storm intensity of 65 mph winds and a pressure of 990 millibars. Grace's movement quickened to 25 mph, as it went speeding off to the northeast. Despite being in a hostile area for tropical cyclone development, Grace strengthened into the morning of October 5, reaching its peak intensity of 70 mph winds and a pressure of 989 millibars. At its peak intensity, Grace was a very small system, less than 100 miles across. In comparison, the widely scattered shower activity of the extratropical low spanned hundreds or even a thousand miles. Throughout the day of October 5, Grace continued northeast, reaching a forward speed of 30 mph, and began to weaken. It was then absorbed by a frontal boundary late on October 5. The combined system caused scattered showers over the British Isles over the next day but no damage resulted.

Grace at its peak of a small, intense tropical storm in the extreme northeast Atlantic.

Grace's track.