Being a Weather Observer

Sunday night, I was woken by lightning flashes to our south, illuminating the silhouettes of far off mountains and dissipating through clouds across a quarter of the sky. They were the manifestation of easterly waves, regions of low atmospheric pressure moving through the tropics. Since Costa Rica’s location near the equator prevents the formation of fronts like those that bring changes in the weather in the United States (the Coriolis effect is too weak at this latitude), easterly waves are one of the special features of this region that have brought us here. Although their relationship with thunderstorms was evident just by looking out my window, the exact connection is an area of active research and one of the primary objectives of the OTREC project.

The following morning brought a more quantitative perspective to the problem, as the Gulfstream-V jet sent back data in real time about conditions in the atmosphere to the southwest. Its course brought it into contact with some of the same storms I saw overnight. Our headquarters’ location on the northwest coast of Costa Rica means the two patterns the plane flies roughly bookend our position, allowing the onboard scientists to sometimes catch a glimpse of weather some time before it reaches those of us on the ground, then watch it move off into the east. Ground-based RADAR and satellite images might provide a similar perspective, but the pictures on this blog attest to the tangible connection to weather that only the plane provides. One doesn’t need to be an expert in dropsondes or plane-based RADAR to see the difference between watching the world from only 3 miles up versus more than 22,000 (about the altitude of a geostationary weather satellite).

As a first year graduate student, seeing these types of systems up close is an incredible opportunity for me to make the connection between the data that climate models produce and the real world. I’ve worked with satellite rainfall data and studied weather over the ocean from the comfort of an office, but I never could have pictured the scale of a fully-developed cumulonimbus or the drama of a convective storm backlit by the Pacific sunset, washed with shades of red and pink punctuated with all-consuming lightning flashes. It will be hard to forget those images when I get back to my desk.

A National Hurricane Center (NOAA) weather map from early in the morning on August 12. Though it displays a lot of information at once, the main point is that fronts (curving blue and red lines) are notably absent in the tropics, and in their place are easterly waves (marked here with short black lines labeled "TRPCL WAVE").