fmzip: That is a question that we face on a regular basis, for the simple reason that ALL popular "weather reports" for the Virgin Islands ALWAYS show that same and alarming forecast of "clouds/sun/rain" each and every day. You need to ignore those forecasts, as difficult as that sounds. They simply means that on island, somewhere, sometime, there is a chance for a brief and localized shower, but that nearly all of your day will be sunny, and most places on island will not see any rain at all that day. Clouds do pass by, though, and this is the tropics. If a large cloud is headed your way, and its base looks darkish rather than white, you may be in for a brief shower. If it lasts more than a minute or two, this can send folks on the beach scrambling for temporary shelter. We just head into the water, where you will also [spoiler alert] get wet. The sun then pops out again, usually for most of the day, and more often then not with a rainbow as your prize. So mission number one is to ignore the popular forecasts.
However, there is a qualifier. Twice a year, usually sometime in April-May, and again in November or even early December, there can be a period of a week or more with unsettled weather, and a number of mostly cloudy or overcast days in a row. These periods seem to align with shifts in the trade winds, from coming from a bit north of east in winter, to a bit south of east in summer. We have been in one of these phases for the last week, although that weather system finally seems to be about to leave the VI. Despite the normal trade winds coming from east to west, this pattern streams off Central or South America, and moves from west to east, higher up in the atmosphere (the lower level winds on island remain mostly east to west). It has been fairly rare over the last week to see a shadow, and the output of our solar electric panels has dropped a lot. So if you arrive just at the start of this pattern, you could face a mostly cloudy to overcast week, but still with infrequent showers. But you will be on St. John, and a cloudy day there is still a very fine thing. Also, you don't have to be as careful about setting up your beach chairs under the sea grapes, or using suntan lotion. In really unsettled weather, choose a beach with some picnic pavilions (Maho, Trunk, or Hawksnest), where you can shelter from the rain if and when needed.
One way to relieve yourself of this concern is to check the Spice Cam, especially in the days leading up to your arrival, and see how often those "rainy days" in the forecast have full sun and strong shadows:
www.stjohnspice.com/spicecam/
I just installed a weather station up on Gifft Hill, that provides a continuous record of air temperature, average wind speed and gusts, wind direction, rainfall, humidity/dew point, and barometric pressure; you can access that here:
http://www.wunderground.com/personal-we ... =ICRUZBAY5
If you switch the weather station from daily to weekly view, you will see that we got about an inch of rain over the last week, but that the actual duration of each rainstorm was very short, and that several took place at night. We love to hear heavy nighttime rains on our metal roofs, and our thirsty cisterns are also happy.
If you would like to read a serious weather forecast for the area, this "Scientific Forecaster Discussion" from the National Weather Service in Puerto Rico is updated daily, and is the real deal, entirely different from the popular "sun/rain/clouds" icon forecasts:
http://www.wunderground.com/DisplayDisc ... e=Cruz_Bay
Satellite weather images of the entire Caribbean and Atlantic are visible here, and can give you a pretty quick sense of basic weather patterns:
http://images.intellicast.com/WxImages/ ... e_anim.gif
For a somewhat closer look, try this link:
http://wwwghcc.msfc.nasa.gov/cgi-bin/ge ... mframes=11
For satellite weather zoomed in on the Virgin Islands, with commentary, try this site that I created:
http://www.vi-satweather.com
One more weather related item of interest is the ocean temperature. This varies with the season and the time of day, as well as by how sunny it is, and you can check this out via a great ocean temperature monitoring station at Lameshur Bay, here:
http://tidesandcurrents.noaa.gov/physoc ... id=9751381
This monitoring station is at VIERS in Lameshur Bay:
www.islands.org/viers.
They also publish tide levels and forecasts:
http://tidesandcurrents.noaa.gov/waterl ... id=9751381.
While St. John doesn't have enough shoreline to amplify tidal currents into large swings in water levels, these tidal currents can be substantial, especially in places with nearby islands, such as The Narrows between St. John and Great Thatch Island. Tidal currents reach peak flow four times a day, and their strength is modulated by the phase of the moon.
A final note on two other weather issues: We can and do experience tropical storms. These can pass by anytime from June to November, but mostly cluster into August and September. The ocean is vast, and both the eye of a storm and St. John are very small. The vast majority of these tropical storms pass by far away, and don't affect local weather at all. Once in a while, one comes close enough to do so, but these pass by very quickly, and typically only affect weather for a day. Once in 10 to 20 years, they can pass close enough to present much more serious issues, with very heavy rains and/or extreme winds. Those storms WILL affect or even cancel your vacation. The last item to mention is Sahara Dust, which arrived about a week ago, and comes and goes during the summer, generally clearing out for good by October. Here is a VIOL post that I wrote on this subject:
http://www.virgin-islands-on-line.com/v ... =1&t=27307
With one cloudy week already behind us in the April-May season, the odds of having great weather for your visit look pretty good. Enjoy your stay!
All the best,
Kevin
