Tropical Wave 01: Where Did The Rainfall Go?

Tropical weather is a fickle thing and Tropical Wave 01 is just the latest example.

The atmosphere is a fluid environment as we try our best to capture the ever-changing situation with in situ observations and remote sensing.

On the ground, automated weather stations collect winds, temperature, humidity, and rainfall, usually at airports, and atmospheric soundings give us properties of a slice of the atmosphere at one time. High above Earth, satellites give us an abundance of data on the dynamic atmosphere. All of this data is then fed into supercomputers to produce numerical weather prediction models.

Even with all of that, the forecast can be busted. That’s what happened today. The forecast was wrong. We’re not happy about it either because we lose credibility, but it happens when you live in a tropical area. Why?

The atmosphere was just too stable (for now).

We’ve been monitoring this tropical wave for a few days and all indications (even until Tuesday night) showed periods of showers and isolated thunderstorms affecting T&T on Wednesday. Yet, we awoke to mostly sunny skies.

The Tropical Wave

A tropical wave has an axis, but it’s really a larger atmospheric feature that brings a myriad of weather – sunshine, showers, thunderstorms, and Saharan Dust may follow.

According to the National Hurricane Center, the axis of this wave moved across T&T overnight. However, based on the characteristic wind shifts (east, then east-northeast, then briefly east, then east-southeast to the southeast, returning to east) and satellite imagery, the axis of this wave finally moved across the Lesser Antilles this morning.

Ahead of a tropical wave, atmospheric moisture surges but the overall atmosphere is not optimal for shower or thunderstorm development. Following the wave axis, the active weather follows.

Fighting Wind Shear

Over the last 24 hours, wind shear across the Eastern Caribbean has been strong, above 60 knots, the highest in the Caribbean Region. This westerly wind shear kept showers east of the Lesser Antilles even as the wave axis moves westward.

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