Our team watched with intrigue as Tropical Storm Danny was completely absorbed by a storm developing off the coast of North Carolina early Saturday morning, verifying the forecast for a hybrid storm to explode over the Gulf Stream and churn northward. That spun heavy tropical rain into the region from south to north, resulting in localized flooding, and by the time the rain ends, we expect to find some amounts of half a foot!

In this image, the colors indicate temperature as measured by the infrared satellite, where colder temperatures indicate taller, stronger clouds, often associated with thunderstorms. Notice the white coloring at the center of the mass of thunderstorms from 9 AM Saturday…that white coloring is at the end of the temperature scale, indicating -80 degrees Celsius. In other words, the tops of the thunderstorm clouds when Danny became a strong hybrid storm were -112 degrees Farenheit!! This was an impressive development of a mass of thunderstorms that would all move north to douse eastern and central parts of Southern New England with substantial rainfall. In fact, visible satellite imagery shows little bumps in the center of the thunderstorm mass as Danny neared New England…these represent “overshooting tops” - thunderstorm clouds that grew so tall and vigorous that they broke through the atmospheric cap where clouds shouldn’t even develop! This was all evidence of a very impressive display of a rapidly blooming hybrid storm.

As of midday, rainfall totals have crossed two inches for most Southern New England communities, and will continue climbing until rain shuts down during the late afternoon.

As for wind associated with this hybrid storm, radar indicated a rotating center elevated from the ground, and wind in excess of 60 mph just a few thousand feet above the surface. I actually issued this post at 2:35 PM and admitted defeat on damaging wind for the Cape, having received no reports at that time, and explaining how seriously we take it when the forecast doesn’t pan out. I’m updating this post at 4:35, after the core of damaging wind DID move through, and verified the forecast for 60+ mph gusts when Horseshoe Shoals, Nantucket, gusted to 61 mph! Trees have been downed and power knocked out. Those who took action to tie down boats and bring in patio furniture undoubtedly have saved damage from being done. Up and down the coastline, winds have been approaching or exceeding Tropical Storm force gusts of 39 mph, with isolated to widely scattered tree and power line damage elsewhere. The wind will slowly subside Saturday evening.

The storm center will zip by Saturday evening with rain and wind ending last on the Outer Cape and Downeast Maine, then drier air aloft will allow for sunshine and temperatures rising to near 80 on Sunday. An upper level disturbance and weak surface cold front may touch off a shower or thunderstorm for some communities.

Drier and comfortable weather is expected to begin the week.

Matt