Before Irene even reached hurricane status, a NASA satellite saw heavy rainfall and hot towering thunderstorm clouds around the storm's center this weekend. That heavy rainfall is expected as Irene continues to track through the Caribbean today. The Tropical Rainfall Measuring Mission (TRMM) satellite passed over Irene when it was a tropical storm on August 21, 2011 at 0024 UTC (8:24 p.m. EDT August 20). Data collected with this orbit showed that Irene contained numerous powerful thunderstorms with TRMM's Precipitation Radar revealing that some thunderstorm towers near the center of the storm were reaching to heights above 15 km (~9.3 miles).
Those "hot towers" are called "hot" because they rise to such altitude due to the large amount of latent heat. Water vapor releases this latent heat as it condenses into liquid. Back in 2004, researchers Owen Kelley and John Stout of NASA's Goddard Space Flight Center, Greenbelt, Md., found that a tropical cyclone with a hot tower in its eyewall was twice as likely to intensify within the next six hours than a cyclone that lacked a tower. Irene had those hot towers and did intensify into a hurricane.
The National Hurricane Center noted on August 22 that Irene is expected to produce total rainfall accumulations of 5 to 10 inches across Puerto Rico, The Virgin Islands, the Dominican Republic, Haiti, the Southeastern Bahamas and The Turks and Caicos Islands. Isolated maximum amounts of rainfall may reach up to 20 inches.