The Latest on Newly Formed Tropical Storm Karen

Tropical Storm Karen developed this morning near the southern Windward Islands. Karen has maximum sustained winds of 40 mph and is moving WNW at 13 mph (see Fig. 1). 

Fig. 1: Latest update on Tropical Storm Karen (NHC)

Karen is relatively disorganized due to strong wind shear (see Fig. 2) thanks to an upper-level trough to the northeast of the storm. As Karen continues its WNW (& eventually NW motion), the wind shear is forecast to gradually lessen allowing the storm to increase in intensity as the storm moves toward Puerto Rico (see Fig. 3). The intensification is expected to be gradual, however, due to dry air continuing to plague this system through mid-week. Numerical guidance indicates dry air will be pulled into the center of the storm through mid-week, which should keep Karen below hurricane status as it approaches Puerto Rico. 

Fig. 2: Current wind shear (University of Wisconsin)

Fig. 3: Forecast track & intensity of Tropical Storm Karen (NHC)

The uncertainty in Karen ensues as we head into late week into the weekend. Numerical guidance is suggesting a ridge will start to build north of Karen by late week (see Fig. 4). Guidance indicates the ridge north of Karen will continue to build into the weekend (see Fig. 5). Depending on the strength/placement of the ridge & the location of Karen, will determine if Karen goes out to sea in the Atlantic or begins to curve toward the west (possibly posing a threat to the U.S. sometime during the first week of October).

Fig. 4: Late week 500 mb Heights (Tropical Tidbits)

Fig. 5: Late week 500 mb Heights (Tropical Tidbits)

It is too early to forecast what Karen will do once we head into next weekend with so much uncertainty in key variables that will help steer the storm, but there is a realistic chance Karen *could impact parts of the U.S.. Continue to check back for frequent updates throughout the week on Firsthand Weather.