Published on 21 Aug 2012

Three tropical storms that need watching

After a sporadic spell of activity during recent weeks in the tropics, things seem to have suddenly sprung to life. In both the Atlantic and Pacific ocean basins, clusters of showers and thunderstorms are becoming more organised and forming named storms.

In order for a tropical cyclone (known as hurricanes in the Atlantic and typhoons in the Pacific) to form, there are a few favoured conditions that need to be present for development to take place.

What is needed for a tropical cyclone to form?

One of the most important factors is a source of warm, moist air with an ocean surface temperature of 27C or more.

The supply of heat and moisture effectively acts as fuel for any potential storms. This is why tropical cyclones die when they move over land, as their energy supply is cut off.

Winds at the surface also need to converge together. This forces the warm, moisture-laden air upwards where it subsequently condenses and forms stormy cumulonimbus clouds.

Another important balancing act is having winds that don’t change direction too much with increasing height in the atmosphere. This allows a potential storm to develop further without getting torn apart.

Finally, there needs to be some spin from the rotation of the earth to get storms to circulate. This is why they almost always form at least five degrees either side of the equator.

Typhoon Tembin

At the moment, typhoon Tembin is over the warm waters of the Philippine Sea, rapidly gaining strength and heading towards Taiwan.

The latest forecast slams this typhoon into Taiwan during Thursday local time as a very powerful storm with steady winds of 135mph and gusts of 165mph. Winds of this strength would result in major damage.

The wind won’t be the only concern, with copious amounts of rain likely to bring severe flooding and landslides, as well as a storm surge for coastal areas.

Image courtesy of CIMSS showing Tembin circled in red and Bolaven circled in orange

Tropical storm Bolaven

This storm is currently over open waters in the Pacific Ocean west of Guam. Whilst this storm poses no threat to land for at least the next five days, it is set to strengthen into a typhoon.

Some weather computer models are keen to steer Bolaven towards south east China early next week, but at this stage there is a lot of uncertainty as to exactly where this storm will end up going.

Tropical depression Nine

Currently located 645 miles east of the Leeward Islands, further development in the next 24 hours will see this cluster of thunderstorms getting even more organised and become tropical storm Isaac.

The latest forecast strengthens this storm to a hurricane later on Wednesday local time, which is subsequently expected to drift gradually westwards through the Caribbean.

Torrential rain and steady winds of around 110mph could affect the Dominican Republic, Haiti, Jamaica and Cuba later this week. However, there is some uncertainty with the exact track because if the storm hits the rugged mountains on some of the islands, it could get torn apart.

Image courtesy of NOAA showing Nine circled in yellow

I’ll be tweeting on the progress of these storms, so follow me on Twitter for updates – @liamdutton

Tweets by @liamdutton

3 reader comments

  1. Andrew Dundas says:

    Useful and well written blog!

    Could it be that the Pacific Ocean is some extra store of warmth? Might that greater warmth in the winter months sometimes drive Pacific winds up into the Arctic region, thus pushing Arctic winds down into the Atlantic areas?

    Might those north-bound Pacific winds also increase precipitation in the far north?

  2. Richard says:

    Tues 28th Aug. Over Royal Wootton Bassett, there were good optical phenomena. The 47-degree Upper Circumzenithal Arc, 22 degree haloe, and left hand Solar Parhelia

  3. suranga says:

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