HURRICANE: Erika weakens to 40 mph

By Nathan McCollumnTROPICS — Airplane investigation over the last 12 hours indicate that Tropical Storm Erika is having problems.

The current National Hurricane Center forecast is the best estimate of where the actual center is located. Satellite imagery suggests that at least two other low pressure areas are contained within the mass of convection.

It is not unusual for a tropical cyclone to reform a stronger center when the system is disorganized. However, Erika has several areas trying to be the dominant surface low pressure. This greatly reduces the possibility of any strengthening until the center battle is over. Also, the shear area I discussed yesterday came early and is actually impacting the western and northern quadrants of Erika. This shear is likely the reason a new center is trying to form.

Basically, this is not a well organized system and (with the stronger wind shear areas ahead of Erika) this storm may not become a hurricane. The location of Tropical Storm Erika is Latitude 16.5 N – Longitude 60.4 W with sustained winds of 40 mph. The central pressure has risen to 1008 mb and Erika is moving west at 10 mph. Tropical storm force winds extend 105 miles from the estimated center.

The visible satellite picture shows the mass convection area to the east of the original surface low pressure. A burst of convection just to the east of the original center may be the new center forming. The infrared satellite picture shows an elongated type of convection with an absence of storm activity on the west and north side. This is the result of wind shear in the upper levels of the atmosphere. The attached water vapor picture shows the ridge in place and no signs of weakness for several days.

As discussed yesterday, disorganized storms such as Erika tend to keep moving in one direction and not be impacted by the ridge energy. The models have started to see this trend and have moved the forecast more to the south. The actual NHC five day forecast has moved more to the south and west than yesterday. While this seems to put Florida more in the path, Erika may not even survive the shear. Also, this is a low confidence forecast because the exact center will likely change over the next 24 hours and that will require model adjustments and forecast modifications.

So, this remains a slow moving tropical storm and we have plenty of time to monitor the progress of Erika. We will see how it does over the next 24 hours. The next advisory will be Thursday.

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