First storm of season may be forming

The current system is located about 1,025 miles south-west of the southern most Cape Verde Islands with a 1010mb low pressure centre. (Photo: nhc.noaa.gov)

by Terry Ally

BRIDGETOWN, Barbados, Monday June 14, 2010 - Forecasters are monitoring a strong and large weather system in the far eastern Atlantic Ocean, just off the Cape Verde Islands, which could develop into Tropical Storm Alex sometime this week, if current trends continue.

If that happens, it will the first time in the 124 years since record-keeping started that a Cape Verde storm will form in June.

Some computer models indicate that it could become a threat to the Caribbean, others show that it will be a rain-laden open wave by the time it arrives. 

Either way, forecasters have warned Caribbean residents to get ready.

"The bottom line is that conditions in the tropical Atlantic are already favorable for tropical cyclone formation and people should go over their emergency plans and be ready for the next tropical cyclone threat no matter when it might coming knocking on the door," say forecasters at the US National Weather Service in Puerto Rico.

Warm oceans

Historically, storms tend to form in this area in September. In June they form in the Gulf of Mexico and in July and August they gradually begin to form further and further south and east. One of the many factors which influences cyclogenesis is the sea surface temperature (SST). For a cyclone to form it requires an SST of at least 26.5C (80F).

The current SST just off the Cape Verde Islands, where this system is located, is 28C with some sections around 30C.

This was one of the indicators used by forecasters Professor Bill Gray and Philip Klotzbach from Colorado State University to predict 18 storms, 10 hurricanes and five major hurricanes this year.

In their June forecast they noted that above-normal SSTs in May and reduced trade wind strength in the eastern Atlantic Ocean coupled with lower sea surface pressures in the Caribbean imply "a very favorable thermodynamic environment for tropical cyclone formation and intensification in this area" during the most active part of the hurricane season. It also correlates, they say, with favourable wind conditions to help storms to maintain their strength.

Computer models

The current system is located about 1,025 miles south-west of the southern most Cape Verde Islands with a 1010mb low pressure centre estimated around 8 degrees north and 38 degrees west on Monday morning. 

That was about 1275 miles east of the southern Windward Islands. It is travelling westward at 10 to 15 miles per hour. Over the last 48 hours it has become better organised and the National Hurricane Centre in Miami says there was a "high chance" - about 60% - that it could become a tropical depression in 48 hours.

At this stage, computer models have no consensus on the path. Some are split between bringing the system straight through the central Caribbean later in the week while a few others take it into the open Atlantic.

The current environment favours continued strengthening up to the Windward Islands when the upper levels winds are expected to be hostile. They will either hinder further strengthening or will destroy the system altogether. 

However, these forecasts change daily as more oceanic-atmospheric data is fed into the equation.

The annual Atlantic hurricane season runs from June 1 to November 30 each year.