Although hurricane season officially begins on June 1st, we already have the 3rd named storm of the season with the arrival of Tropical Storm Colin, which formed yesterday at 21:30 UTC (4:30 pm CDT) in the southern Gulf of Mexico about 120 miles north of the Yucatan Peninsula. Colin originated from a wave of low pressure that propagated across the tropical Atlantic and northern coast of South America and into the southern Caribbean. As thunderstorm activity picked up, the wave slowly organized into an area of low pressure as it turned northward and passed over the Yucatan. After entering the extreme southern Gulf of Mexico, the low became sufficiently developed to become a tropical depression (TD #3). However, the circulation was not very well organized as it was under the influence of moderate southwesterly wind shear, causing most of the thunderstorm activity to be located well east of the center.
This overpass from the GPM core satellite was taken this morning at 07:53 UTC (3:53 am EDT) on 6 June 2016. The image shows DPR (radar) rain rates in the center of the swath and GMI (microwave) rain rates in the outer swath overlaid on enhanced IR data from GOES-East. GPM shows two large areas of rain associated with two areas of deep convection. The northernmost area contains areas of heavy rain rates of up to ~75 mm/hr (~3 inches per hour, shown in magenta) and shows some evidence of banding (curvature), indicating the presence of a cyclonic circulation. However, the National Hurricane Center (NHC) is reporting that Colin is poorly organized with multiple small-scale circulation centers: one near this area of convection and the other well to the west-northwest. At the time of this image, Colin was a minimal tropical storm with maximum sustained winds reported at 50 mph by NHC.

Colin is expected to strike the Big Bend area of the Florida Gulf Coast sometime during the overnight hours this evening. However, little change in intensity is forecast as Colin is still under the influence of moderate vertical wind shear and too disorganized to intensify significantly.