The Savannah scientist is in the middle of a seismic study of the Caribbean for an international relief agency and has long thought of Haiti's capital as one of the most vulnerable areas on earth for a powerful earthquake.
"Our big nightmare was Port-au-Prince, Haiti and the nightmare's come true," said Watson, a former NASA scientist who now serves as an advisor for the Caribbean Catastrophe Relief Insurance Facility. "What happened was a magnitude 7 earthquake. That's a major earthquake, particularly given the geology of that area. It's extremely dangerous. There are a lot of steep, deforested hillsides in Haiti. So there was a lot of what we call liquidation, soil starts vibrating and it essentially turns from a solid to a semi-liquid. Tremendous structure collapse, we think as many as 20,000 people may have been killed in this event."
Watson says that figure could double or even triple in the aftermath, when the country's already limited services are crippled.
And because of strong aftershocks, which could continue for days.
"They've already had aftershocks that have measured 5.6," said Watson. "It would not be surprising to see some more 5.6. And a 5.6 is a bad earthquake on its own. So you've already got structures that are damaged. The ones that have not collapsed are more likely to collapse in these aftershocks. However bad you can imagine, that's how bad it is."
And Watson didn't just imagine yesterday's earthquake in Haiti.
Armed with the information in his study, he expected it.
"We knew it was a generational thing," he says. "We knew we had 20 to 30 years of extreme vulnerability. And unfortunately, it happened right at the beginning of that window. Earthquakes are really nasty because we know where, we just don't know when."
And Watson is not alone now in saying there's no telling when Haiti may recover from this.