Fred Update

Fred formed way in the east of the Atlantic. I believe it was already a hurricane going over the Cape Verde islands. I was shown pictures today of seas damaging a pier. I have not heard too much more about damage.

Six years ago, Fred formed around the same area a little further south, but did not intensify as fast. It did become a hurricane, then dissipated as it curled, for a short while was heading easterly, then got pushed back westward. By this time it had fallen apart and it did not get organised again, but the remnants of the storm tracked a good way across the Atlantic.

Looking at the discussion of Fred, it is likely to be pulled apart in the short term. Then the track forecasts give a range of possibilities, including heading westward.

Latest (5AM AST, 1st September) forecast discussion:

http://www.nhc.noaa.gov/text/refresh/MIATCDAT1+shtml/010849.shtml

These discussions tend to be very helpful in gauging how much confidence the forecasters about the forecasts.

These days, both track and intensity forecasts can be pretty accurate out to 24 hours or so.

This paragraph from the discussion has a lot of information in it:

Fred is expected to move between west-northwest and northwest for the next 72 hours as a mid-level ridge to the north of the cyclone gradually builds westward. After that time, a turn toward the north-northwest and north is forecast due to a deep-layer trough currently over eastern Canada that is expected to dig southeastward over the central Atlantic and erode the ridge. The NHC model guidance is in decent agreement on this developing pattern change. However, there are significant differences in the model solutions with the HWRF, GFS, and GFDL models keeping Fred stronger and making the northward turn sooner, whereas the weaker solution models like the UKMET and ECMWF take a weaker and more vertically shallow cyclone farther west before turning it northward. The official forecast track is a little south of the previous advisory track, mainly due to the more southerly initial position, and follows a blend of the weaker UKMET and ECMWF solutions.

At the end, we learn the current forecast track is further south than the previous advisory. The discussion notes this is mostly because Fred did not move as far north as expected over the previous period.

Disagreements in models are usually informative, often indicating there is more uncertainty in the forecast. Sometimes the forecasters have good understanding of why the models are disagreeing, different models have different strengths.