Diving in Thailand - Calendar of when to go where?

[jlevine]

I am considering planning a trip to Thailand but am not sure what month. I see a lot of posts in this forum asking what the weather is like during a given time of the year. Is there by chance a calendar that says "In January, this place is usually good while another place might not be good?" I realize that such statements would be generalizations and that conditions can vary from one year to the next. I'm just looking for a starting place.

Thanks!

[ayeshacantrell]

Generally speaking the gulf is best March to October and west coast the opposite.....

[idivethesea]

I agree as well, my favorite time is Jan/Feb in the Andaman Sea.

[aquamarin]

Similan & Surin Islands are open 1st November through 30th April - during that time, diving is awesome here at the west coast (apart from occasional "freak" weather of course. Diving is still very good at Phi Phi and Phuket May through October, but there is a risk of rain or a bit of swell Koh Tao is typically good April through October.

[lord khram]

Generally speaking the gulf is best March to October and west coast the opposite.....

Maybe true for Koh Tao, but for the Eastern Gulf around Koh Chang, this is exactly the time of year you do not want to be there.

Indeed most shops on the island close May to September.

[ayeshacantrell]

Sorry LK -

[Buadhai]

Maybe it helps to think of tropical weather in terms of the Inter-tropical Convergence Zone (ITCZ). This is the area near the equator where winds from the northern and southern hemispheres meet and form what sailors call 'the doldrums'. This is because most air movement in the doldroms is vertical (not good for sailors) rather than horizontal.

In the northern hemisphere, places north of the ITCZ generally experience dry (semi-dry?) trade winds out of the northeast. Almost all of Thailand is north of the ITCZ from about November through April, hence the dry season.

Places south of the ITCZ generally experience wet "monsoon" winds out of the southwest. Most of Thailand is south of the ITCZ from about May through October, hence the wet season.

On a weather satellite photo the ITCZ is the band of clouds that extends around the world near the equator.

The ITCZ moves north and south based on global temperatures. (It also meanders based on local surface temperatures.) As the northern hemisphere heats up in summer, the ITCZ moves north. It's position throughout the year is somewhat asymmetrical because the northern hemisphere has more land mass than the southern hemisphere.

Why then do Phuket and Koh Tao seem to have opposite diving seasons? During the wet season Phuket takes a direct hit from the monsoon winds while while the eastern gulf coast is somewhat shielded by the peninsular land mass. During the "dry" season the trade winds can pick up considerable moisture and energy from the Gulf of Thailand and cause foul weather in places like Koh Tao and Koh Samui.

You can get a fair idea when the seasons will change and what weather to expect by keeping your eye on where the ITCZ happens to be. Of course, predicting the weather is iffy at best and things like tropical storms and unusual high and low pressure zones can disrupt the ITCZ.

Real meteorologists are invited to step in and correct errors in the above.

[lord khram]

Sorry LK -

No need to appologise.
Just thought I should point it out as the summer weather in Koh Chang can quite often be inclement. Many of my friends that spend lengthy periods on the Island all leave during this period.
Also in the Gulf is Pattaya / Samae San where diving is possible all year round, but I think the less said about Pattaya diving the better.

For anyone that is interested the web page in the att'd link provide in my experience an accurate description of the conditions you can expect (Koh Chang ()

[Quero]

jlevine, some of the answer to "when is the best time to dive in Thailand" depends on what you are looking for. The consensus is that the very best diving we have to offer is in the Andaman via liveaboard to the Similans and Surins national parks, which include the islands themselves and the surrounding seas. So if that's what you're aiming at, you need to think about conditions on the west coast of the country.

As others have said, on the west coast we have generally great conditions between November and May, but as Buadhai says, there is some variation from one year to the next and it's best to check updated weather pattern maps to know what to expect. That doesn't help you plan, though, does it? What I generally tell people is that weather can still be changeable in the months of November and April, simply because we never really know ahead of time exactly when the winds will shift from the southwest monsoon (our wet season) to the northeast monsoon (our dry season). Some years we get perfectly dry and calm Novembers and in other years the entire month is still unsettled weatherwise. The same is true for April. So if you are looking for flat water, your best bet is sometime from December to April. If you want the clearest water, come earlier in the dry season. If you want the best chance for big pelagics like manta rays, come later in the season when the plankton levels are more pronounced. Mid-December to mid-January tend to see a lot of visiting Europeans (when the economy isn't keeping them home). Most of my American customers seem to come in November or February/March.

[Buadhai]

^Welcome back!