Tropical Storm Bertha finally forms, heading into Caribbean

August 1

Bertha, the second named storm of the 2014 hurricane season, formed east of the Lesser Antilles Thursday night.  Bertha is currently a tropical storm with 45 mph sustained winds. This is almost exactly when the second named storm forms climatologically, and the overall activity as measured by ACE (Accumulated Cyclone Energy) is almost exactly what the average is for this date.


Tropical Weather Dashboard
System type: Tropical Storm
Intensity: 50mph, 1007 mb (updated 2 p.m. EDT)
Location: 115 miles north-northwest of Barbados
Intensification potential: Low (confidence: medium)
Landfall potential: High (confidence: high)
Days from possible landfall: Less than one
Zones to watch for possible landfall: Lesser Antilles (confidence: high)
Will if affect VA/MD/DE beaches? No (confidence: high)
Will it affect D.C.? No (confidence: high)


 


Enhanced satellite image of Bertha from 8:15am EDT… low clouds show up as yellow, while high clouds show up as white. (NOAA)

Nearly a week after leaving the coast of Africa, the easterly wave that we’ve been tracking all week was upgraded to Tropical Storm Bertha at 11 p.m. ET Thursday(0300 UTC on Aug 1).  Two reconnaissance aircraft were flown into and around the disturbance yesterday afternoon; one to sample the storm’s environment and one to measure the storm’s central pressure and peak winds.  It was found to contain tropical storm force winds, but lacked the thunderstorm activity at the time to be classified as a tropical cyclone.  As soon as persistent thunderstorms fired up near the center yesterday evening, it was upgraded at the next advisory time.

As I mentioned in my blog yesterday morning, this timing was anticipated.  It needed to escape the dry air associated with the Saharan Air Layer, and I expected that it would escape its grip by Friday morning.  Judging from its appearance, it is in a somewhat moister environment now as it heads for the Lesser Antilles.  However, Tropical Storm Bertha is still not in an ideal environment – far from it: there is now fairly strong westerly wind shear and environmental dry air remains nearby, though not as dry as earlier this week.

Given the marginal conditions, Bertha is forecast to remain a 45-50 mph tropical storm through the next five days, and is not forecast to become a hurricane.  Tropical storm warnings are in effect for Barbados, the central Lesser Antilles, Puerto Rico, and the Virgin Islands.  The Dominican Republic should be added to the list later today.  It is extremely likely that Bertha will recurve out into the open Atlantic over the eastern Bahamas and not affect the mainland U.S..  The storm’s intensity when it’s north of Hispaniola will depend greatly on how well it fares as it passes over/near that very mountainous island.  I have a couple long radar loops available; one from Barbados and one from Martinique (Puerto Rico’s will be added tomorrow).

3-day track forecast from NHC as of 8am EDT. (NOAA)
3-day track forecast from NHC as of 8am EDT. (NOAA)

Once again, if I look through the records, there have been just a couple of storms during all of August that were tropical storms where Bertha is now and turned northward toward Puerto Rico.  The historical track that almost exactly matches Bertha’s forecast track is a major hurricane from 1893… you can probably pick it out on the map below:


Tracks of all August tropical cyclones that were at tropical storm intensity and within 100 miles of where Bertha is this morning (indicated by the gray circle). (NOAA)

 

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