Some Homegrown Tropical Problems?
All the focus recently has been on Hurricane, now Tropical Storm Bertha over the central Atlantic. It’s time to take a closer look at what has popped up not far off our coast this morning. A fairly well developed area of low pressure has spun up on the end of an old frontal boundary that has pushed offshore back at the end of the week. The low is clearly visible on satellite and QUIKSCAT images below. The QUIKSCAT image is a satellite derived product that allows the orbiting satellites to estimate the current surface wind speeds and directions…sort of like a really long range police radar. It can detect the speed and direction the clouds are moving. Cool stuff that is great during tropical season.

(Image 1 & 2: Visible Satellite/GOES Floater & QUIKSCAT - Courtesy NOAA)

The low, about 130 miles southeast of Charleston, is moving slowly parallel to the coastline. There is a chance that this low could slowly develop over the next few days. The main issue is right now how small it is. Smaller circulations have a more difficult time developing quickly than larger tropical lows. This low is also a “hybrid” low. It has to totally detach itself from the old front so it can become fully “warm core” and complete its tropical transition. There is very little chance of this posing a problem for us but it is something that we will watch closely as it moves northeast. A stronger trough of low pressure should move off the coast on Monday and help push it further away from us and whisk it off to the northeast. Needless to say, some of the forecast models do show this becoming a tropical depression by Tuesday. We will watch it closely for you.

New INVEST - 94L could threaten the Lesser Antilles:
A new tropical disturbance has developed over the far southwestern Atlantic between the Cape Verde islands and the Leeward Islands. The National Hurricane Center (NHC) has designated this area 94L, meaning that they will begin more close monitoring and forecasting of the disturbance. The area of circulation associated with 94L is very large and embedded within some deep tropical moisture, so all indications point to this area developing. All the tropical forecast models do bring 94L to depression strength by the middle of the week but differ in long term tracks.

(Image Courtesy: Colorado State University)

You can see on the initial forecast plots above, if 94L does develop it may very well impact the Lesser Antilles by the weekend.  Some of the more global models say that Bertha will pull 94L north of the islands while some do not develop it at all. We do anticipate that this will become a depression or Tropical Storm later this week. We will continue to watch the forecast guidance daily as it comes in. Too early to tell if it could eventually head toward the United States.

Bertha Hangs On: 

The latest visible picture of Bertha shows that the downgraded hurricane is now a Tropical Storm. The winds have fallen to around 65mph but the storm still has a very impressive circulation and still look somewhat healthy on all the data from satellite reconnaissance.  The U.S. Air Force Hurricane Hunters will investigate the storm later to day to get a better idea on the structure of Bertha. She has not been moving much over the last day or so and that has allowed the surface winds to churn up colder water under the center, which is called upwelling. This is slowly robbing Bertha of the fuel that she needs to keep going. Recent data does show a new slow movement to the northwest and if Bertha can get back over warmer water, she may very well re-gain some strength. As for Bermuda, a Tropical Storm Warning is in effect for the island and the outer bands are visible on radar from the Bermuda Weather Service.

(Image Courtesy: Bermuda Weather Service - Radar)

Bertha will gain the title of the longest lasting tropical cyclone in July (12 days) if it can hold on through Tuesday, which it will. All the forecast guidance agrees that Bertha passes very near Bermuda then is swept northeast over the cooler North Atlantic by the end of next week.

We will watch our coastal waters closely….stay with this week!

Chad Watson
Live 5 Meteorologist

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