Comment Unusually warm and moist air is returning to the Mid-Atlantic ahead of the remnants of Tropical Storm Nicole, which will move through the region on Friday. While Thursday is calm, there will be a chance of rain on Friday that will increase from the morning, with intermittent showers throughout the day. The main impacts in the DC area will include on and off periods of heavy rainfall that could lead to isolated flash flooding and gusty winds from the south and southeast. Given several atmospheric rotations associated with the remnants of Nicole, a tornado threat may also develop. Torsion chances are somewhat higher south and southeast of Washington, toward southern Maryland, Richmond, and the Virginia Tidewater. Tropical Storm Nicole is hitting Florida, which will flood the eastern US The National Weather Service’s Storm Prediction Center has placed the D.C. area at a 1 out of 5 tornado risk level, while areas to the south are in a 2 out of 5 risk zone. Increasing cloud today with showers from the south tonight. Scattered showers overnight-Fri. A.M. with a quiet afternoon. Additional showers & isolated strong thunderstorms Fri eve. Potential hazards: damaging winds, isolated tornado and localized flooding. #VAwx #MDwx #WVwx #DCwx pic.twitter.com/bOVc28gKXD — NWS Baltimore-Washington (@NWS_BaltWash) November 10, 2022 In addition, the Weather Service has placed the area in a Level 1 out of 4 risk for excessive rainfall. Chances for heavy precipitation will increase to the west and northwest of the DC area. Synchronization: Rain chances increase Friday morning, particularly southwest of the area, and become possible after sunrise. Additional waves of rain move through during the day. The rain should end late Friday night. Cover: Showers are expected to come in waves and maybe some thunder. Rains will be quick but can be quite heavy at times. Risks: The main concerns are heavy rain, gusty winds and the risk of an isolated tornado or damaging wind gusts. The chance of flooding is quite low because the area has been rather dry lately. Rainfall Forecasts: A widespread 1 to 1.5 inches is most likely. Towards the mountains, 2 to 3 inches could fall. Southern Maryland and the Delmarva Peninsula see possibly a half inch to an inch.
How will Nicole affect the region? By Friday morning, the center of Nicole’s weakening will be over central Georgia, as shown below, with rain moving north through the Mid-Atlantic. The storm is characterized by very high wind circulation. The retreat of high pressure to the north will help tighten the pressure gradient across the Mid-Atlantic, thus keeping wind speeds high. Expect winds to frequently gust 20 to 30 mph Friday and possibly higher in any storms. As Nicole transitions from a tropical to a midlatitude storm, a warm front will form (red lines above) that may be the focus for any tornado activity. Meanwhile, a strong cold front and deep dive in the jet stream will approach the East Coast from the Ohio Valley. The center of Nicole’s remnants will join this front, perhaps near the spine of the Appalachians, as a plume of deep tropical moisture moves north to the east of the storm. Strong lifting on the western side of Nicole’s remnants will interact with tropical moisture to create a band of potentially very heavy rain over the Appalachians, with more rain to the east. By Friday night, the remnants of Nicole will quickly exit to the northeast and skies may begin to clear by midnight.
Because strong winds and tornadoes are a danger While the fuel for the types of storms that could produce tornadoes will be limited in the DC region, wind shear (change in wind direction and or speed with altitude) will be significant. This combination of components can create the basis for low-top rotating storms. These cells, in turn, may bring damaging wind gusts (50-60 mph) to the surface in some places, as well as create brief tornadoes. Inland tornadoes spawned from tropical remnants tend to be short-lived and weak, but these characteristics also make them difficult to detect with radar, thus preventing early warnings. At this point, the Storm Prediction Center feels the highest tornado threat will be just south of DC, however, we caution that this zone could extend further north if the atmospheric mass remains unstable through the late afternoon and early afternoon . Rainfall totals will depend heavily on the track. As of now, about an inch total in Washington seems reasonable. A shift of the forecast track further east would bring higher totals closer to the region. The area has been quite dry recently, so the threshold of rain causing flash flooding locally is high. Overall, the projected track of Nicole’s remnants has shifted west, somewhat reducing possible rainfall in the immediate area. Here are the amounts displayed by different models:
European (ECMWF): 0.50-1 inch+ US (GFS): 0.75-1.5 inches American (NAM): 0.50-1 inch Canadian (GEM): 0.75-1.5 inches ICON: 0.75-1.5 inches
Additional track changes are possible, which will affect the precipitation forecast. But we don’t expect big changes now that we’re a day into the event.
