Dorian may be a candidate for a similar extreme rainfall to Harvey (2017) and Florence (2018) as blocking high pressure systems either side of Dorian cause a slow turn over Florida that could take up to 3 days to execute. The NOAA/WPC 7-day rainfall forecast already indicates a large swath of 15-20 in. of rain for much of eastern Florida.

Dorian may slow on approach to Puerto Rico today, lose some intensity tonight crossing the island then re-emerge north of Puerto Rico reaching hurricane strength in 2 days. Dorian turns more west-northwest due to steering guidance of a strengthening Bermuda High on the weekend. Tropical cyclone models indicate Dorian could become a major hurricane in the day 4 to 5 period while east of Florida.

The D1, D2 drought areas in southwest/southeast Brazil look to receive some beneficial rainfall during the medium-range period agreed upon by both the GFS and ECM. The wetter trend for these areas which desperately need the rain is a forecast change (from drier outlook late last week).