Wednesday, June 29, 2011

Tropical Storm Arlene (2011)

Storm Active: June 28-30

Arlene originated from one of many tropical waves emerging off of the west coast of Africa during late June. On June 25, this particular wave, at the time moving onto the Yucatan Peninsula, began to interact with a broad trough of low pressure over Central America and the waters to the north. This interaction generated an area of scattered showers and extending westward from the wave itself into the western Caribbean Sea. The next day, on June 26, the wave moved over the central Yucatan, and thunderstorm activity concentrated along it, extending from north to south. On June 27, the wave emerged into the Bay of Campeche, and immediately rain bands began to form about a low pressure center in the southeasternmost area of the Bay, just north of the Mexican coast. The low tracked slowly west-northwestward and strengthened, but upper level winds were not yet favorable, and the circulation was not yet well-defined. However, wind shear diminished further on June 28, and the low was upgraded to Tropical Storm Arlene that evening.

Arlene maintained a slow west-northwest motion overnight, and the rain bands, formerly being sparse, quickly increased in convection early on June 29. The cyclone, which had only minimal tropical storm strength up to this point, intensified as it turned more to the west. By later that day, rain and wind began to sweep across the Mexican coast. Despite its proximity to land, Arlene's winds continued to increase, and the cyclone reached its peak intensity of 65 mph winds and a minimum pressure of 993 mb just before landfall near Cabo Rojo, Mexico. Before losing its water supply, which provided fuel for Arlene's convection, it also developed an eye-like feature.

After landfall early on June 30, Arlene began to quickly weaken over land, becoming a tropical depression that afternoon, and dissipating that evening. The remnants of Arlene caused rain in Mexico for an additional day before moving west into cold Pacific waters. The moisture from Arlene, although causing significant flooding in parts of northeastern Mexico, had a more positive effect on areas of Texas. In that state, numerous thunderstorm activity was generated by the trough associated with Arlene, temporarily relieving drought conditions. 25 fatalities, including 11 direct and 14 indirect, are associated with Arlene.

Arlene near peak intensity shortly after landfall in Mexico. Although a strong tropical storm, Arlene's center (and eye feature) are still not well defined.

Track of Arlene.