DISCUSSION: The Atlantic hurricane season officially runs between 1 June and 30 November. Although, the past five years have seen at least one named system before 1 June including this year (Subtropical Storm Andrea). In general, relatively few storms form in the early part of the season (or before the start of the season) compared to later in the season (~September). Between 1851 and 2015, there have been 112 tropical storms (maximum sustained winds 34–64 kt) and 37 hurricanes (winds >64 kt) in May–June in the Atlantic compared to 578 tropical storms and 398 hurricanes in September. The source of energy for tropical cyclones is the evaporation of water from the ocean, and warmer water provides more energy for evaporation. In addition, water has an enormous heat capacity, so it takes a long time for water to warm up. Hence, the largest reason why there are usually relatively few storms early in the season is because the water has not had a chance to warm up yet where tropical cyclones typically form.
If a storm does form early in the season, an important question to ask is where in the basin is it most likely to form. Water tends to warm faster in the western part of the tropical Atlantic, so early season storms tend to form in the Gulf of Mexico, in the Western Caribbean, or near the east coast of the U.S. The graphic above shows the origin point (red dots) and tracks of all storms that have formed between 1 and 10 June during 1851–2015. All the storms in the Atlantic basin originated in the western part of the basin. The hurricane season in the east Pacific begins earlier (15 May) than that in the Atlantic, so there is also a cluster of storm formation in the East Pacific. The bottom line is that early storm formation in the Atlantic basin tends to occur where impacts on land are relatively likely.
Finally, another important question to ask is whether there is any correlation between early season and later season activity. In other words, can storm activity in May–June be used as a predictive tool for activity during the peak of the hurricane season? Unfortunately, there is very little correlation between activity in different parts of the hurricane season. Conditions could be conducive to storm formation for an extended portion of the hurricane season, or they could be especially active for a month or so and be especially hostile to storm formation the next month; it varies from season to season.
Despite usually fewer storm formations in the early part of the hurricane season, it is important to always be prepared if you live in a hurricane-prone region, especially considering early season storm formations tend to occur close to land in the western part of the basin. Remember it only takes one storm to be catastrophic.
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©2019 Meteorologist Dr. Ken Leppert II