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Why is November So Wet in the Virgin Islands?

St. Thomas — Were the torrential rains we saw yesterday on all three islands normal? The rain was normal, the flooding wasn’t. Most of us remember last year after hurricanes Irma and Maria struck the territory, the following weeks of recovery were met with heavy rains. On some days, even hampering the operations of WAPA, Viya and government agencies conducting recovery efforts.

If you missed out on yesterday’s madness, the Consortium captured some of the crazy moments.


5 inches in 11 Hours

With the help of Dr. Kyzer, an instructor at the University of the Virgin Islands, I managed to track down rainfall recorded on St. Thomas. By 11 a.m. yesterday, 5.66 inches had fallen in St. Thomas — an overwhelming amount of rainfall for islands that have long suffered with drainage issues and runoff that is potentially hazardous to coral reefs and other fragile ecosystems.

Government offices territory-wide were closed and school was dismissed early. Waste Management Authority also noted that the sewage transport system on island could be disrupted as the infrastructure was overwhelmed by rain water.


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According to data sets provided by NOAA and other partner organizations, November, December and January have about 30 to 50 wet days on average in the Caribbean region. So the rain we saw yesterday is normal during this time of the year. What isn’t clear is if the territory is receiving above average rain this season compared to previous years.

Organizations like the St. Thomas Recovery Team began asking residents so send in pictures and videos or rainfall, mudslides and other storm related damage.


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NOAA meteorologist in Puerto Rico also noted that, the auto data feed has been problematic for some time and worse since storms last year. The buoy array in our territorial waters also does not collect precipitation data, that data is apparently land based.

Every year, North America endures blistering winters that sometimes affect the Caribbean archipelago. While the Caribbean remains significantly warmer, the chill in the air is enough to make locals wear sweaters until it warms up in early February.

Climates to Travel: Source

According to Climates to Travel, the northern slopes receive more rain than other parts of the island. The Bovoni area and much of the south side of St. Thomas are generally very dry areas, home to cactus and other plants that can survive under extremely dry conditions.


Unique Weather Patterns

St. John and some parts of the BVI create their own weather patterns because of their mountainous terrain. So, why do mountains — hills in our case — create rainfall? Like other places with dramatic peaks, winds carry moist air over the land on all three islands.

When air reaches a hill or slope, it rises because the mountains are in the way. As the air rises, it cools very quickly, and because cool air caries less moisture than warm air, there is usually visible signs of precipitation with fog or rain following.

Early morning clouds forming over St. John and the BVI

This is similar to the phenomena that produces volatile weather in the form of hail storms.

I started writing this article around 5:45 this morning while watching dark clouds tower (and grow) over St. John and Tortola. The sun is now up, the clouds have passed and those same clouds are dumping rain back into the ocean on the northside of St. Thomas.

This is why early morning showers on each island is so common. As the day progresses and warms, we generally have warmer, dryer days. If a cold front from the north moves in midday, the same weather pattern emerges, sometimes with increased intensity and heavier, longer periods of rainfall.


Unique Islands

Crown Mountain on St. Thomas is the highest peak on the three main islands, and it too creates its own weather patterns. Though not as dramatic as islands similar to St. John and Tortola when considering their topography and elevation.

Google: Source

St. Thomas has an elongated shape, with approximately 2 to 3 peaks that create significant fog and precipitation, St. John and other islands in the BVI have several dramatic peaks that form valleys, creating more dynamic landscape that often creates dramatic weather patterns.

Image of the Nadir Gut a year after a portion of it collapsed during Hurricane Irma, threatening multiple homes. The wall has continued to crumble away as water undermines it.

Take some time out of your day and watch our sister islands in the east and you’ll start to wonder why there are more clouds over St. John and the BVI and clear skies in St. Thomas and St. Croix.

For anyone that cares, I studied meteorology in college before I realized it wasn’t for me and switched to a teaching program. Who said you can’t teach people things with articles. 😉  Sorry St. Croix, I need to learn more about the weather patterns on island before I take a swipe at you.

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Images appeared first on The Virgin Islands Consortium