Puerto Rico

Weather Elements Limit Storms in Tropics

All is quiet in the Tropics and things may stay that way.

There has been some chatter recently that the remains of Tropical Depression No. 4 would redevelop north of Puerto Rico in the coming days. Thunderstorms have been developing.

The threat for further development has diminished today and there are several weather features preventing development. The storms are disorganized — they need to form a closed area of circulation — and also surrounded by dry air — they need warm, humid air to develop.

The storms are also battling some wind shear and running into a trough of low pressure. Computer models have also stopped further development.

The tropics overall are not very active. Nothing is really in place to trigger storm development.

There is an expansive area of dry air over the Atlantic Ocean helping to keep the tropics quiet. No tropical systems are forecasted to develop this week.

There are several things needed for a tropical storm or hurricane to form:
• Warm ocean temperatures, at least 80 degrees.
• Unstable atmosphere, to support thunderstorm development.
• Humid air.
• Low wind shear.

Right now water temperatures are warm, but the other ingredients are lacking.

You have most likely heard of the weather phenomena El Niño or La Niña which can dictate the weather pattern for a long period of time. The Madden-Julian Oscillation is similar. It can have an influence on tropical weather, but on a shorter time frame.

Every 30 to 60 days, the MJO, an area of thunderstorms near the Equator, can move around the globe. If those storms are strong enough and move into the right location they can increase tropical storm formation. Right now, the MJO is weak.

So far this Atlantic hurricane season, we have only seen three named storms. Still, the National Oceanic and Atmospheric Administration is predicting an above-normal season overall, with between 11 and 17 named storms.

Hurricane season runs through Nov. 1.

CORRECTION (July 11, 2017, 6:35 p.m.): An earlier version of this article said this hurricane season calls for a below-average number of storms. That was based on the prediction this spring by Colorado State University hurricane researchers. Their forecast has since been updated due to a lack of a significant El Niño developing. The official forecast from NOAA has and continues to call for an above-average season.

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