Subtropical Storm Melissa Develops off Northeast U.S. Coast

Subtropical Storm Melissa developed off the northeast coast of the U.S. on Friday.  At 11:00 a.m. EDT on Friday the center of Subtropical Storm Melissa was located at latitude 38.5°N and longitude 69.6°W which put it about 190 miles (300 km) south of Nantucket, Massachusetts.  Melissa was moving toward the south-southwest at 3 m.p.h. (5 km/h).  The maximum sustained wind speed was 65 m.p.h. (105 km/h) and there were wind gusts to 80 m.p.h. (130 km/h).  The minimum surface pressure was 995 mb.

More thunderstorms developed near the center of a large low pressure system off the northeast coast of the U.S. on Friday morning and the National Hurricane Center designated the system as Subtropical Storm Melissa.  Melissa initially began as an extratropical cyclone along a slow moving cold front off the east coast of the U.S earlier this week.  The cold front moved east of the surface low pressure system and the surface low stalled underneath an upper level trough.  More showers and thunderstorms began to develop in bands and the low pressure system started to look more subtropical.

The circulation around Melissa was characteristic of a subtropical storm.  There was a well defined center of circulation visible on satellite images.  However, many of the stronger thunderstorms were occurring in a band that wrapped around the northern portion of the circulation.  Bands in the other parts of the circulation consisted primarily of showers and lower clouds.  The circulation was drawing cooler, drier air into the western and southern parts of the subtropical storm.  The wind field around Subtropical Storm Melissa was large and asymmetrical.  Winds to tropical storm force extended out 350 miles (565 km) from the center in the northeastern part of Melissa.  Tropical storm force winds only extended out 100 miles (160 km) to the southeast of the center of circulation.

The intensity of Subtropical Storm Melissa may not change much during the next 12 to 24 hours.  Melissa will remain under the middle of the upper level trough during the rest of Friday.  The winds are weak in the middle of the trough and there will not be much vertical wind shear.  Subtropical Storm Melissa will be over water where the Sea Surface Temperature is near 24°C.  So, there will not be a lot of energy in the upper ocean to support intensification.  The upper level trough will move eastward on Saturday and westerly winds will blow toward the top of Melissa.  The westerly winds will cause significant vertical wind shear, which will start to weaken Subtropical Storm Melissa.

Since the winds are weak in the middle of the upper level trough, Subtropical Storm Melissa is unlikely to move much during the rest of Friday.  Stronger westerly winds will steer Melissa to the east during the weekend.  On its anticipated track Subtropical Storm Melissa is forecast to move away from the U.S. during the weekend.  The large circulation around Melissa will generate large waves which will affect the south coast of New England and the Mid-Atlantic states.  Coastal flooding could occur in some locations.