Excerpts from Jim Conrad's
from the September 11, 2011 Newsletter
issued from Mayan Beach Garden
Inn 20 kms north of Mahahual, Quintana Roo, México
Here on the peninsula's eastern coast prevailing winds blow from off the ocean in the east, so those interior storms that form to our west just drift farther westward. During the interior's rainy afternoons, storms don't form over us or the water because it's much cooler on and beside the ocean, and for storms to form you need stark temperature differences. You need warm surface air to bubble up through cooler air, to high altitudes.
For the last two or three months, even as afternoon rains drenched the interior, for the most part it's stayed dry here on the coast. Rains mostly came when tropical depressions or "areas of disturbed weather" formed in the Caribbean, then wandered over us, sometimes dumping several inches of rain over a period of days.
Lately a new trend has begun and Marcia says it'll develop more fully until things really get soggy in October. That is, right before dawn, storms or showers form out over the water and drift over us. What's happening is that during the night air over the water cools dramatically, but the ocean water remains warm - - about 86°F (30°C) off our coast.
Therefore, right before dawn, air immediately over the warm water starts bubbling up through the night-cooled air above it, until it reaches an altitude where condensation occurs. Then rain falls as the cloud drifts over us, sometimes lots of rain, with lightning and thunder, just about when I'm jogging.