10:46 a.m. update: The National Hurricane Center has upgraded Bertha to a hurricane.  Maximum sustained winds are estimated at 80 mph, with a minimum pressure of 998 mb.

Original post from 10:25 a.m.

Since Friday morning, Bertha crossed the Leeward Islands, slid just south of Puerto Rico, clipped the eastern tip of the Dominican Republic, passed over the extreme eastern Bahamas, and is now centered 400 miles east of West Palm Beach, Florida.  During much of that journey, it was a weak and disorganized tropical storm, but is now nearing hurricane intensity.

Tropical Weather Dashboard (updated at 10:46 a.m.)
System type: Hurricane
Intensity: 80 mph, 998 mb (updated 10:46 a.m. EDT)
Location: 400 miles east of West Palm Beach, FL
Intensification potential: Medium (confidence: high)
Landfall potential: Medium (confidence: medium)
Days from possible landfall: 3.5 – 4
Zones to watch for possible landfall: Newfoundland, Canada (confidence: medium)
Will if affect VA/MD/DE beaches? Indirectly… increased surf on Tue. pm – Wed. am (confidence: high)
Will it affect D.C.? No (confidence: high)

Infrared satellite image of Bertha from 9am EDT. (NASA)

Having a weak tropical cyclone pass over the eastern Greater Antilles was generally a good thing, as many of those islands have been suffering from a drought.  The strongest wind gusts in Puerto Rico were in the 30-40 mph range, and rainfall totals were generally in the 1-4 inches range with some isolated reports of 10 inches in the highest terrain.  A buoy near the U.S Virgin Islands reported a gust to 72 mph.  It did cause some power outages and flash flooding in Puerto Rico and the Dominican Republic, but overall, just a short-term nuisance that should help the drought situation.

Rainfall map of Puerto Rico and the U.S. Virgin Islands from Tropical Storm Bertha. (NOAA)

Conditions are favorable for further intensification, and it is forecast to become a minimal hurricane later today or tomorrow.  If Bertha does become a hurricane, it will be the earliest second hurricane since Dolly in 2008! Also, the last time both the A and B storms became hurricanes was in 1992: Andrew and Bonnie.  At 8:30 a.m. this morning, a NOAA aircraft reconaissance flight reported a partial eyewall was present, so it is certainly becoming an organized system for the first time.  The track forecast keeps Bertha away from the U.S., but close enough to stir up some enhanced surf along much of the East Coast.

Probability of tropical storm force winds over the next five days. (NOAA)

Bertha now has about two more days left as a tropical entity.  It will remain a fairly strong storm after that, but transitioning to an extratropical cyclone as wind shear jumps up to 60+ mph and ocean temperatures plummet to sub-70°F.  It will likely bring stormy conditions to Newfoundland on Thursday, and high seas to the northern Atlantic after that.  Otherwise, the Atlantic basin is quiet, and no new storms are expected to form this week.