Alex formed over the Atlantic on 14 January, a very early date for an Atlantic hurricane.
By Jochen Kerkmann, Ian Mills, Mark Higgins and Neil Fletcher (EUMETSAT)
On 14 January a hurricane formed in the middle of the Atlantic, a very rare event for the winter season. Thus the hurricane, named Alex, became the first hurricane of the 2016 season.
With a central pressure of 973 hPa and winds over 140 km/h (77 knots) — estimates from AMSU measurements on 15 January at 5:04 UTC (source: CIMSS) — it moved towards the Azores where it was expected to hit the islands in the evening of 15 January. The Portuguese weather service (IPMA) issued red alerts for the central and eastern Azores for winds, high waves and heavy rain.
According to NOAA's historical hurricane tracker database no hurricane has been observed in January over the northern Atlantic in the last 60 years. In January 2006 Tropical Storm Zeta came close, when it formed in nearly the same position over the Atlantic, reaching 1-minute sustained winds speeds of 100 km/h (65 mph).
Zeta can be seen in this MSG Airmass RGB image, with a cold (white) Central Dense Overcast area and a marked upper level cirrus outflow.
The birth of Hurricane Alex, out of a cut-off low over the Atlantic, can be seen in the sequence of Airmass RGB images from 12, 13, 14 and 15 January (Figure 2) and in the animation, Meteosat-10, 09 January 201612:00 UTC–15 January 08:00 UTC (MP4, 15 MB).
More details of the convection around the centre of the developing hurricane can be seen in the Met-10 IR10.8 animation, 13 January 09:00 UTC–14 January 09:00 UTC (MP4, 8 MB).
Figure 3 shows the winds in the region of the storm — the centre of circulation can be seen clearly. This image is from 10:18 UTC on 15 January. The data are from RapidScat, a scatterometer temporarily mounted on the International Space Station. The data are processed by the Ocean and Sea Ice SAF team of KNMI, The blue wind arrows show the winds from the HIRLAM model.
The development of Alex is very typical for a subtropical hurricane: a slow-moving (stationary), cold-core, extra-tropical cyclone converts to a warm-core, tropical cyclone over an area with relatively high SSTs (but not necessarily 26 °C).
It should be noted that (so-called) Medicanes fall into the same category of subtropical hurricanes. One of the most spectacular Medicane cases is described in the 2011 case study Development of a tropical storm in the Mediterranean Sea.
An Atlantic Hurricane…in January (NOAA Earth Observatory)
Hurricane Alex (CIMSS Blog)
Hurricane Alex: earliest Atlantic hurricane since 1938 (Liam Dutton's C4 Weather Blog)
Rare January Hurricane Alex Hits The Azores; Hurricane Warnings Issued (The Weather Channel)
Previous case studies
Record-breaking hurricane Pali (12 Jan 2016)