An unsettled Friday I got up around 2 AM Friday morning to start my day, which is typical when storms are around. As the coffee was brewing, one thought entered my mind: active tropical systems never sleep. The southeast has received its fill of Debby, a storm that will be long remembered there. While the impacts on Maine appear to be minor in comparison, the dynamics here aren’t anything to dismiss.  Friday 6 AM to 6 PM - A warm front moves into the region during the day. The rain shield ahead of it pushes northward, raising dew point temperatures in the wake. By late afternoon, much of the state will be sitting in the warm sector. Steadier rainfall early tapers to isolated showers later. With the unstable convective conditions aloft, I can’t rule out an afternoon thunderstorm.  Overall, the day won’t be a washout, but it won’t be pleasant. Expect areas of fog around, along with patchy drizzle. Cloud cover is expected to hold over the region, but pokes of sun may work in, which if that happens, it increases the risk for a shower or storm to develop. The main concern is overnight into Saturday This “energy helicity index” model prog deserves definition. In a nutshell, helicity is the corkscrew low-level spin in the atmosphere. When tornadoes are discussed, the terms “updraft” and “inflow” are tossed around, which is more or less what helicity is. The energy part of this equation is fueled by convective available potential energy (CAPE). That element is part of the dynamics with tropical systems or tropically infused frontal boundaries. Around here, our convection (thunderstorm / heavy rain shower development) is usually sun-driven. In this situation, a sharp cold front is working up against tropically warm, unstable energy. Given the timing, this poses a nocturnal threat, something we do not ordinarily experience.  Our best chance for severe storms comes overnight into early Saturday morning as the cold front sweeps through to push the storm out. While damaging wind is the likelier threat, the amount of spin being picked up by radar could trigger a tornado warning. That should be taken seriously in case there is an actual tornado. Be prepared for it.  Friday 6 PM to Saturday Noon — The frontal boundary moves swiftly through the region overnight, with rain ending soon after sunrise over the south and west and exiting DownEast by midday. I can’t rule out an isolated shower, as the air column dries out in the afternoon, with the best chance for that over the higher elevations over the interior. Expect a breezy Saturday with increasing sun, warm temperatures, and falling dew points.  The short term model ideas hint at training and back building of showers and storms. This is where the flash flood threat is likely to occur. With the heavy rain passing through overnight, travel impacts due to low visibility from torrential rainfall, fog, ponding on roadways, and the potential risk of a flooded roadway, especially in the mountains. Remember to turn around, don’t drown. Small rivers, brooks, and streams are likely to rise quickly. Trail and dirt road washouts are possible. For those camping out, you may want to find a motel to stay in given the situation. Another potential tropical storm in the pipeline to watch 'Tis the season. Click on the image to find out how |
Mike Haggett
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