Hurricane Alex: earliest Atlantic hurricane since 1938
A rare and impressive feat took place in the Atlantic Ocean today, as subtropical storm Alex turned fully tropical and became a hurricane.
According to the NOAA’s historical hurricane tracker database, Alex is the first Atlantic hurricane to form in January since 1938, as well as being just the second on record for the month of January.
This is remarkable because the Atlantic hurricane season runs from 1 June until 30 November, so to get a hurricane forming in January is significant.
Every so often, tropical storms or hurricanes form in December, just after the end of the season, but to see this in January is very unusual.
Hurricane Alex’s formation
Alex started off as a subtropical storm on Wednesday afternoon – exhibiting characteristics of both tropical and non-tropical systems.
According to NOAA, they normally include including a broad wind field, no cold or warm fronts, and generally low-topped thunderstorms displaced from the centre of the system.
However, on Thursday, Alex became a category one hurricane, with sustained winds of 85mph and stronger gusts.
Hurricane force winds extend 25 miles from its centre, with tropical storm force winds 150 miles from its centre.
Unusual formation conditions
What is particularly interesting about Hurricane Alex is that it has managed to form over ocean waters that are just 20C.
Normally, hurricanes need ocean waters that are 26C or above in order to form.
In this case, the anomaly has been that temperatures in the upper part of the troposphere – around 6 miles up – have been much colder than normal at -60C.
It’s contrasts in temperature, pressure and humidity, both vertically and horizontally, in the atmosphere that drive the weather on our planet.
So despite the ocean water temperatures being much colder than normally needed, the anomalously cold troposphere has generated enough instability for thunderstorms to thrive and allow a hurricane to form.
Hurricane warnings for the Azores
The Azores Meteorological Service has issued hurricane warnings for the Azores, covering the islands of Faial, Pico, Sao Jorge, Graciosa and Terceira.
Tropical Storm warnings are in force for the islands of Sao Miguel and Santa Maria.
As well as strong winds and a storm surge at the coast, potentially flooding rains are expected, with 3-5 inches possible widely, and as much as 7 inches over the higher hills and mountains.
Such large amounts of rain will have the ability to cause landslides, which may affect roads around the islands.
The latest forecast from the National Hurricane Center then takes the storm northwards across the mid-Atlantic Ocean well west of the UK, weakening significantly this weekend.
I’ll be keeping a close eye on the progress of Hurricane Alex and posting updates on Twitter – @liamdutton