The National Hurricane Center has been threatening to name Tropical Storm Bertha for four days, and the system finally fulfills all the criteria for a tropical storm.
What Makes a Tropical Storm?
A weather system must meet certain criteria, in order to achieve ‘tropical storm’ status. Those criteria include:
- The system must have a closed low pressure center.
- The storm must have surface winds of 39 miles per hour or greater.
- There must be significant thunderstorm activity near the center of the system.
Bertha is of particular interest because it is on a track that storms which have impacted the US east coast have taken in the past. Bertha is currently forecast to curve out to sea, but a minor change in the forecast track could bring a landfall on the Carolina coast in the middle of next week. Fortunately, the probability of that is low.
However, Bertha will hit the Caribbean Islands with strong tropical storm winds and heavy rain.
The Cape Verde Season
Bertha marks the start of the Cape Verde hurricane season. Once waters in the eastern Atlantic become warm enough to support tropical cyclone activity (80 degrees), easterly waves coming off Africa have a whole ocean in which to develop. Like Bertha, many past Atlantic tropical systems could be followed from one end of the ocean to the other.
The Cape Verde season begins around the end of July and ramps up to a peak in early September.
Where’s Bertha Now, And Where’s She Going?
Bertha is currently close enough to Barbados for the island to feel the fringe effects: wind gusts up to 30 miles per hour. The storm will pass directly over Martinique tonight, with winds gusting over 60 miles per hour. Bertha will cross Porto Rico on Saturday and skirt the Bahamas on Sunday.
It will be disconcerting to residents of coastal North Carolina, recently impacted by Hurricane Arthur’s 100-mile per-hour winds, to see a strong tropical storm heading directly towards them. But the weather pattern should protect them from any impact except for some rough seas and rip currents.
The persistent trough that brought traffic-snarling snow and bitter cold to the central US last winter, but has provided delightfully cooler-than-normal temperatures during the summer, will probably save the east coast from any impact of Bertha. As the storm feels the effect of the jet stream, it will turn sharply to the right and head northeast out to sea.
Eventually, Bertha will transition into an extra-tropical cyclone. It could cross the ocean and impact Europe next week.
How Powerful Is Bertha?
Bertha’s top winds are now 50 miles per hour, and the National Hurricane Center’s official forecast has the storm retaining that strength until it has safely passed the mountainous and tropical-storm-debilitating island of Hispaniola. Moving along the Bahamas, the winds are forecast to increase, and with a brief crossing of the Gulf stream, Bertha could possibly reach hurricane status, though right now it looks like winds will top out around 65 miles per hour.
Bertha can be viewed as the little tropical storm that could. The system has been hampered by very dry air to its north, which kept it from developing into a tropical storm for much of its journey across the ocean. It has also encountered moderate vertical wind shear (change of wind with height) in the last couple of days, but this storm system has kept right on chugging.
Bertha Will Probably Be Considered A Blessing
As long as the winds are not too strong, Bertha will be more good than bad. The Caribbean has suffered from a long drought, and the storm will produce up to three inches of rain in the Lesser Antilles, possibly more in mountainous areas of Porto Rico.
What’s Next For The Tropical Atlantic?
The next named storm will be called Cristobal. He is not yet in sight; however, easterly waves will come off the African coast with regularity in August and September, and it’s only a matter of time. Now that the water has warmed and the dry air that inhibited Bertha has receded to the north, that time may be short.