Bill formed as an indistinct cluster of thunderstorms in the Gulf of Mexico, just north of the Yucatan Peninsula. It made landfall on the Texas coast at 1645GMT on Tuesday. There were gusts to 85km/h and a storm surge of one metre, but it was always likely that the accompanying rainfall would cause the most problems.

The rain from Bill will add to the accumulated rainfall over the last month or so. May was the wettest month in Texas history, virtually wiping out years of drought in a matter of days.

Bill is expected to track northwards and then northeastwards in the coming days, taking it across Oklahoma, northwestern Arkansas and southern Missouri. Places directly beneath Bill’s core can expect in excess of 150mm with local totals of 250mm.

That Bill should produce such heavy rainfall may seem surprising, as cyclones which form over warm ocean waters tend to dissipate fairly quickly over land as they lose their source of energy.

In this case, Bill is expected to re-intensify as a result of the ‘brown ocean effect’, whereby energy is provided by the warm, saturated soils of Texas and Oklahoma which have not had time to dry out after May’s deluge.

Consequently, river levels, already at the highest levels in many decades will not be able to absorb much of the imminent rainfall before overflowing and causing extensive flooding in the coming days.

Source: Al Jazeera