From Dr. Jeff Masters' WunderBlog (www.wunderground.com)
As this record-breaking third busiest Atlantic hurricane season in history unfolded, I marveled that earthquake-ravaged Haiti managed to dodge significant rain-making tropical storms throughout the peak months of August, September, and October. Cruel fate will not allow Haiti to escape the entire season unscathed, though, as a late-season November storm already proven to be a killer--Tomas--takes aim at Haiti.
Tomas has struggled mightily over the past few days, and is now a tropical depression. However, even if it does not reach hurricane strength, Tomas is still likely to bring heavy rains capable of causing disastrous flooding in defenseless Haiti. It doesn't take much rain to cause a flooding disaster in Haiti--ordinary seasonal heavy rains have killed 23 people in southern Haiti over the past month, including twelve people in Port-au-Prince this past weekend.
According to the Associated Press, most of last weekend's deaths occurred when surging rivers burst through houses built in ravines. With the soils already saturated from last weekend's rains, the stage is set in Haiti for a significant flooding disaster capable of causing heavy loss of life.
I believe it is 30% likely that Tomas will stay far enough west of the Haiti earthquake zone so that rains will be limited to 1 - 4 inches to the region, causing only modest flooding problems and little or no loss of life. More likely (40% chance) is the possibility of major flooding due to 4 - 8 inches of rains. Finally, I expect a 30% chance that heavier rains of 5 - 20 inches over Haiti will cause catastrophic flooding like experienced in 2008's four hurricanes. Potential flooding disasters are not possible just in the earthquake zone, but also in northern Haiti and the southwestern peninsula of Haiti. So, keep praying for the people of Haiti, they need all the help they can get.