As of 2100 GMT today Joaquin is still a Category 1 hurricane of 70 knots, racing east-northeastwards towards cooler waters below the 26 °C threshold. These cooler waters and increased shear should cause Joaquin to lose tropical characteristics during Wednesday and become an extratropical depression as it passes near to the Azores Friday and continues towards mainland Europe. The question is, where in Europe will it end up, if at all? The signals are still very mixed!
The latest official forecast from the National Hurricane Center (NHC) in Miami has the remnants of Joaquin as a 35-knot depression at 49N 10W (about 250 km due south of the southwest Kerry coast) by 1800 GMT on Sunday 11th. This is their best estimate, based on all available data at present. This would give some stiff southeasterly to easterly winds and bands of rain over Ireland, southwest England and northwest France.
This is just one solution, put together by both man and machine working together. The problem with the “machine” is that different machines (computer models) are giving very different forecasts at the moment, so trying to decide which is right and which is wrong requires the input of the human. These guys have vast experience with these systems, and it at times like this that this experience is put into action.
But let’s take a look at the different models, starting with the one that has by far performed the best during Joaquin, the European ECMWF. Today’s midday run shows the remnants actually splitting in two and heading off in totally different directions, one to Iceland and the other to Spain! Ireland is sitting pretty there in the middle, with a ridge of high pressure bringing settled conditions. As I said, this model has been the best of late, and one that the NHC have favoured, however on this occasion they seem to be discounting it.
The American model, the GFS, has a totally different solution, with a deep depression right over Ireland. This would bring strong southerly winds and heavy rain during Saturday night and Sunday, in vast contrast to the settled conditions hinted by the ECMWF. The ECMWF tends to be better because it ingests more observational data than the GFS, however the NHC forecast is more in line with the GFS in this case.
The UK Met Office FAX chart (produced by human forecasters) shows a 975 hPa low centred at 54N 18W, or about 300 km due west of Galway. Their own model (UKMO) shows nothing of the sort, with the depression heading through Biscay and northern Spain as it fills during Saturday night and Sunday. This would mean the Met Office are disregarding their own model and are going for something different to the other two as well.
The other models; the German ICON, Canadian GEM, Japanese JMA and US NAVGEM, all show a similar picture of the low ending up somewhere around northwest Iberia by Sunday, much like the UKMO and the southerly breakaway of the ECMWF. This would hint at some consistency and agreement between most of the models, however the forecasting agencies themselves see varyingly different outcomes, and these don’t tend to agree with one another!
What I’m trying to say is no-one really knows what exactly will become of ex Joaquin. It is pretty sure to bring some strong winds to the Azores on Friday, but after that opinions vary. What we do know is that no amount of speculation by me or anyone else is going to affect the many physical processes at play in the atmosphere that will ultimately determine where Joaquin will see out his days. They say a butterfly flapping its wings in Brazil can cause a rainstorm in New York, but fingers tapping on a laptop keyboard usually only generate a lot of hot air, especially when the laptop belongs to a tabloid journalist!