BERTHA reaches hurricane force

General picture from west to east – Monday 4th August 2014
Disturbance fifteen is close to the east coast of Florida, but barely defined as it merges with an occluded front across the south east of the continental United States. What remains of this is very disorganised, but will still bring heavy rainfall along the south–eastern seaboard.

The big ticket today is BERTHA. A reconnaissance aircraft has buzzed the storm and reported that is has reached hurricane force with some lusty eyewall replacement taking place, but limited in altitude, which will almost certainly be the effect of wind shear from the west. The storm is centred around midway between the Bahamas and Bermuda and tracking north at 15 knots over fairly warm water, with measured wind speeds of 65 knots gusting 80. The current hurricane severity index rating is 6 out of a possible 50 points – 2 for size (windfield radius now 150 miles) and 4 for intensity - and expected to peak at 9 - 4 for size (windfield radius 220 miles) and 5 for intensity. BERTHA still has some warm water ahead so a little strengthening can be expected, but wind shear from the east is likely to cap this. BERTHA is very unlikely to progress beyond a category one.

The storm is northbound now but starting to wobble slightly to the east, to pass the south-east Newfoundland on Thursday but then disappear somewhere in the north Atlantic by the end of the week, perhaps retaining storm status but only bullying sailors and soaking the odd puffin. There is little if any chance of significant impact ashore until reaching Newfoundland, however will still put up a decent show.

Disturbance fourteen was on then off then on again. The nominal centre of this is about 600 miles north of the Amazon delta, but aerial imagery shows very little cloud, which would suggest that this has filled.

A weather watch – mainly for rain – along the south eastern seaboard and maybe a weather watch for Bermuda, otherwise stand easy.