Powerful Typhoon Lekima threatens Taiwan as it recovers from a 5.9 magnitude earthquake. The category 4-level storm is probably impacting parts of Taiwan as I write this and is expected to pass north of the island en route to mainland China. Typhoon Krosa is also being watched as it meanders near Japan and other parts of the region. While the western Pacific typhoon season is in full swing, Where are the hurricanes in the Atlantic?
Typhoon Lekima and Krosa threaten Asia
The Atlantic hurricane season started on June 1st and for many people that ominous date can be misleading. As the Earth makes its tilted journey around the Sun, the seasonal cycle brings the Northern Hemisphere in alignment with more direct solar energy. The atmosphere starts to warm up. However, the ocean water takes a bit longer (more on that later). If I think about a roller coaster, August is like the coaster car just starting to creep up that first hill before the plunge. As a meteorologist, I make it a habit to check the National Hurricane Center page daily at this time of the year. The graphic below illustrates that the Atlantic basin is fairly quiet.
Tropical weather outlook in the Atlantic basin as of August 8th.
If you look at the Tropical Weather Outlook posted by the National Hurricane Center on August 8th it says, "For the North Atlantic...Caribbean Sea and the Gulf of Mexico: Tropical cyclone formation is not expected during the next 5 days." Candidly, there is nothing particularly unusual about this, and the question posed earlier is a bit misleading. August is really the transition month for hurricane activity in the Atlantic basin. The graphic below is a very good tutorial. It clearly reveals that hurricane activity is possible in months prior to August, but the climatological peak is around September 10th. The first week of August is still in the "ramp up" phase.
Why is this? It is related to simple physics. According to NOAA, hurricanes require ocean waters to be "at least 79 degrees F (26.5 degrees C) over a depth of 50 meters." An early season trip to the beach can help with my illustration. The water in the ocean at Tybee Island, Georgia is probably pretty cold on a hot and sunny day in May. However, the sand on the beach may be fairly warm. As I have previously written in Forbes:
"Oceans (water) have great heat capacity than land masses because of something called specific heat. Specific heat is defined as the amount of heat for some given unit mass that is required to increase temperature by 1 degree C. Because of its higher specific heat, it takes water longer to heat up or cool down than dry soil (land)."
The peak of the Atlantic basin hurricane season
As we get into August and September, the water is warm enough to support tropical cyclone development. However, the ocean heat content can certainly be sufficient for development in earlier months, and there are signs that ocean temperatures, on average, are becoming warm enough earlier in the season.
If tropical development does happen in August, where is it most likely to be? In a previous series of Forbes articles this season, I discussed where hurricanes are expected to form in June and July, respectively. The graphic provides the answer for August. The season normally starts to transition for "origin" points in the Caribbean Sea or Gulf of Mexico to the central Atlantic. This is what I consider the transition month to the "Cape Verde" hurricane season. The Cape Verde islands sit just west of Africa. By late August and September, much of the tropical cyclone activity originates in this region. In fact, my meteorological "eye" notices a cluster of clouds near that region in the second satellite image in this article.
We'll keep an eye on it.
Where hurricanes are likely to form in August and September in the Atlantic basin.
