Hurricane Matthew – courtesy of Reuters and the Boston Globe.
I noticed an article in the September 2016 Weather magazine from the Royal Meteorological Society entitled “Understanding hurricanes” by Roger K. Smith and Michael T. Montgomery. It was very informative and it starts:
“Hurricanes are among the most fascinating of all atmospheric phenomena. Much of their intricate dynamics and thermodynamics can be explained within the realm of classical physics. However, some of their secrets are yet to be unlocked.”
I like the phrase “some of their secrets are yet to be unlocked“, secrets like how much will they intensify and where are they going next. It’s exemplified by the two tropical cyclones hurricane Matthew and tropical storm Nicole that are currently cruising the waters off the eastern seaboard of the United States. I’ve been reading the forecast discussion on each storm from the National Hurricane Centre [NHC] avidly as I have done for many years. I noticed that in past years many would be hurricanes never made it because of upper wind shear that stopped any further intensification and the storm ended up as a post tropical cyclone to be absorbed by a trough, or even a worst indignity of being gobbled up by an extratropical low. But this season has been a little odd.
Matthew developed into a category five hurricane on September 30th despite considerable wind shear, and against what more NWP models than you can shake a stick at were forecasting at the time. There is no doubt that Matthew was bound to be a hurricane, the early guidance suggested a category one or possibly two hurricane, but category 5 which is what it reached for a time was most unexpected. The track of Matthew has been quite well forecast up till now (6 October), but at the moment there is a lot of uncertainty and little agreement in all the various NWP models about where it will go next. Here’s a look at the Saffir-Simpson hurricane wind scale.
Courtesy of NHC
Theses are some extracts from the NHC forecast discussion about Matthew as it developed and intensified to category five status despite the wind shear that should have severely limited its development.
Now a category five hurricane after an early forecasts of a maximum category two event and despite all that shear.
Tropical Storm Nicole
Nicole seemed to spring out of nowhere on the 4th of October, as most tropical storms often do. The early discussions again talked about a strong wind shear which they thought would inhibit any further real development of the system. Here are a few more extracts from the NHC discussion this time about Nicole.
So despite early forecasts of Nicole fizzling out due to unfavourable conditions, it now looks quite likely that Nicole will reach at least category one hurricane status later today, not bad for a storm that should now be a subtropical depression or remnant low.
So what is going on this season in the Atlantic basin? Tropical storms seem to be doing what they want, totally ignoring the rules laid down in classical physics about tropical cyclone development. Despite all the satellite imagery and sophisticated NWP models we don’t seem to have that firm a grasp about why cyclones rapidly intensify as Matthew has done. Forecasting the track of a tropical cyclone, although good with Matthew and Nicole up to now, is far from perfect, and I’m sure that you’ll remember the “left hook” that hurricane Sandy gave to New York in 2012. But thanks to George Bernard Shaw there is one thing I do know about hurricanes, and that is that in Hertford, Hereford and Hampshire hurricanes hardly ever happen!
Finally I would like to thank the NHC and the forecast discussion they make public, I love the candour that you get from the forecasters there, it would be good to see Met Office show that same quality of openness in the thinking that went on behind their forecasting.
Last night Nicole was updated to Hurricane status despite early forecasts of a quick demise.