A number of people have been asking me if the start of November this year was hotter than other years. After all, it’s only in the last few weeks that it has cooled down enough for me to venture outdoors in sunlight. In the first week of this month, I decided to go for a walk in Aspire Park. Let’s just say that was a mistake! I arrived at 9am, and it was already too hot. I only managed to last 45 minutes before scurrying back to the comfort of my air-conditioned car.
It’s not just our imagination; this year has been hotter than most years, although it wasn’t only the temperature which made things feel so stifling. The oppressive weather was due to a combination of temperature and humidity. The fresher feel to the weather arrived on November 8, when a keen wind forced the humidity out of the city. The maximum daytime temperature didn’t actually change, it was exactly the same on November 7th as it was on 8th, namely 31C. However, the humidity dropped from a maximum of 89% to 61%. This, together with the keen wind, was enough to make 31C change from hot to pleasant.
As well as a late relief to the heat, rain has also been rather late to make an appearance. You may remember back in August, we nearly saw some rain in Doha when a thunderstorm crossed the country. Other parts of Qatar saw some heavy downpours, but the thunderstorm collapsed as it tracked towards the capital and in Doha it wasn’t rain but a dramatic sandstorm that engulfed the city. In an instant the visibility dropped to nearly nothing and an angry wind raged. The wind picked up my friend’s bench and tossed it into his swimming pool.
The duststorm was clearly a dramatic scene, but one which didn’t bring any rain. Only one other year in the last ten have we had to wait longer for rain, and that was in 2009, when the rain didn’t arrive until November 29. Often the rain can arrive months earlier than this; last year for instance, the first downpour after the summer arrived on September 11.
Whilst it was strangely hot and dry in Doha, it was also unusually warm and dry in much of North America. The temperature difference in North America, however, was far more pronounced than it was in Qatar. In Doha, if the temperature is higher than usual, it’s usually only a few degrees above the norm. However, in Calgary, for the first two week of this month, the temperature was around 15C above normal. In fact on November 8, the temperature was 22C above the average. The maximum temperature should be around freezing, but people were walking around in shorts and t-shirts.
As well as being warm, the weather across North America was also strangely benign. The only significant rain was in the northwest of the US and the western parts of Canada. Seattle had the wettest October in its history, and its wet spell spilled over into November.
The reason behind the warm, settled weather over North America is thought to be due to a change in the Pacific Ocean. At the beginning of this year, the temperature of the Pacific was much warmer than usual, but now it’s slightly cooler than usual. The warming is known as El Nino and the cooling is the lesser-known La Nina.
Like El Nino, La Nina usually disrupts the usual weather patterns around the globe. When the Pacific is cooler than usual, there is often enhanced rainfall over Southeast Asia, a colder winter in Japan, and the northwest of North America is usually exceptionally wet. La Nina is also being blamed for the warm, but calm weather seen across the rest of North America.
Obviously we are seeing the expected impacts of La Nina in North America, but how many other of the ‘typical’ impacts of La Nina we will see is rather up in the air, as this is certainly not a run-of-the-mill La Nina.
During a La Nina event, the cold waters in the Pacific don’t cover the entire ocean. Instead, scientists focus on a small part of the Pacific, situated near the equator. Different meteorological agencies have different criteria for La Nina, but it is the ocean temperature in a relatively small region which is important.
This specific region of the Pacific is certainly cooler than usual at the moment, but this area is dwarfed by the huge area of warmer-than-usual water which is just to its north. What impacts this will have on the global weather is unknown.
Those people living in parts of the world where the weather is often disrupted during a La Nina event will be closely monitoring the weather over the coming weeks and months. However, with the strange temperature set-up in the Pacific, there are likely to be other parts of the globe which also experience some extreme weather, and it is the unexpected weather which is often the most dangerous.