We’re watching a tropical disturbance in the Atlantic this week, which could become the season’s fourth tropical storm if it strengthens. If so, it would acquire the name Don. It would also be about seven weeks ahead of average for the fourth storm of the season.

On Wednesday morning, the National Hurricane Center was giving it a 70 percent probability of becoming a tropical depression or a tropical storm by the end of the week as it tracks west-northwest.


(NOAA)

The Colorado State University department of atmospheric science also increased its hurricane outlook Wednesday. It is now predicting 15 named storms, eight of which the department believes will become hurricanes. This is higher than normal — the average per season is 12 named storms and six hurricanes.

The system currently in the Atlantic doesn’t pose a risk of becoming a hurricane anytime soon. The area of thunderstorms is disorganized, and the ocean water temperature beneath it is only marginally warm for tropical cyclone development.

Over the next several days, models are in fairly good agreement on the west-northwest trajectory, though some are unable to track it after just a couple days.


Track forecasts from a selection of 7 global and regional models. (UAlbany)

However, as is typical for this time of year, it will encounter a large patch of dry air and stronger vertical wind shear, which should limit any significant intensification. No model is forecasting this to become much more than a minimal tropical storm.

If this forms, it would be the second system to do so east of the Lesser Antilles in the deep tropics — it is unusual to have such a level of activity in that region so early in the season. Like Bret a couple weeks ago, it may just be a harbinger of an active African wave season once conditions become less hostile to these fledgling cyclones.


Two-day forecast of mid-level relative humidity from the GFS model. Brown shading indicates air that is generally too dry for tropical cyclones. (tropicaltidbits.com)