An unusual tropical storm, Selma, formed recently to the south of the San Salvador coast. Its winds, at worst, are limited to 70km per hour but its rain potential over the country is about 300mm, all within 24 hours.

Selma is unusual in forming so far east in the Pacific. The National Hurricane Center noted in its discussion on Friday morning that Selma is only the second tropical storm to form east of longitude 90W on record, that did not come from an Atlantic basin tropical cyclone.

The land bridge that joins South and North America is slim enough in places that hurricanes can cross from one side to the other without losing their identity.

In the worst case, a hurricane can sit over a country like Nicaragua, being fed by the warm waters on either side.

Hurricane Mitch was such an example: the second deadliest hurricane in history, beaten only by The Great Hurricane of 1780, and devastating for both Nicaragua and Honduras.

Mitch killed 7,000 people in Honduras, 3,800 in Nicaragua and 240 in El Salvador, mostly by rain-induced landslides.

Once again, in late October, all three countries are suffering from the effects of tropical cyclones. These are by no means as powerful but bring threats of a smaller, yet substantial nature.

There has been significant rain over the last five days in Nicaragua and Honduras from thunderstorms that have finally formed a recognisable tropical depression.

In Tela, on the north coast of Honduras, 399mm has fallen so far. Over the island of Roatan, off the coast of Honduras, 287mm of rain has been collected.

The identified tropical depression, 18, has a high chance of becoming a storm, at which point it will be called Philippe. Its forecast track takes it from the northwest Caribbean, towards the Bahamas.

Owen Roberts Airport on Grand Cayman has already reported 110mm of rain, from thunderstorms on the eastern side of this depression.

Tropical storm warnings, which cover wind strength and heavy rain, are in effect for western Cuba and the northwest Bahamas.