Watching For Potential Tropical Cyclone

Written by on May 7, 2015 in Tropics

Update: NHC plans to name Invest 90L, Ana at 11:00 PM EDT.

We are still a ways out from Hurricane Season and we are already beginning to see the first tropical system of the year. Over the past couple of days, we have been watching low pressure off the southeast coast become a little more organized and now shows signs that it may be transitioning to a subtropical storm over the next 48 hours. If this becomes a subtropical storm (or, less likely, a tropical storm) it will be named Ana.

Visible satellite image of Invest 90L as of Thurday afternoon.

Visible satellite image of Invest 90L as of Thurday afternoon.

Right now it’s designated name prior to being upgraded is Invest 90L.

I said it would be classified as a subtropical storm as opposed to a tropical storm. There are slight differences between the two classifications but both share in terms of impact.

Elongated circulation depicted here is consistent with a subtropical system and a closed circulation meaning this could be close to upgrading.

Elongated circulation depicted here is consistent with a subtropical system and a closed circulation meaning this could be close to upgrading.

Satellite imagery shows an elongated circulation which is consistent with subtropical systems and tropical storm force winds extending far from the circulation center. Areas along the North Carolina and South Carolina coasts have reported winds around 20 mph.

Forecast track for Invest 90L

Late cycle forecast models show a broad forecast track which is not surprising from a storm that will be relatively stationary over the next couple of days.

Late cycle forecast models show a broad forecast track which is not surprising from a storm that will be relatively stationary over the next couple of days.

Right now all forecast model tracks are to be taken very carefully considering the stationary movement that will occur over the next couple of days. The general consensus of the potential track does keep it nearly stationary over the next couple of days drifting north or west. There is potential for the storm to make landfall along the South Carolina coast to the southern North Carolina coast.

A trough over the western CONUS will be slow to move eastward over the weekend with models bringing it close enough to the east coast by Monday to pick up the storm and turn it north then northeast as it accelerates away from the coast.

The deep trough over the western CONUS will keep Invest 90L in weak steering currents until the trough travels eastward enough to push it northeastward away from the area.

The deep trough over the western CONUS will keep Invest 90L in weak steering currents until the trough travels eastward enough to push it northeastward away from the area.

Right now we are in a wait and see where the erratic track winds up taking the storm.

Intensity

We do see some general consistency among the intensity forecast for this system.

Forecast intensity shows Invest 90L will most likely be a subtropical storm once it officially becomes a tropical cyclone.

Forecast intensity shows Invest 90L will most likely be a subtropical storm once it officially becomes a tropical cyclone.

The limiting factors for this storm is very dry air being entrained into the storm keeping the potential for intensifying into something major as it sits off the coast. The other limiting factor will be the water temperatures off the Carolina coast. Water temperatures at this time of year are cool compared to August/September which is one reason why tropical system rarely develop at this early stage of the season. As the storm approaches the mainland, weakening is very likely 3 days from now.

Dry air (orange) being drawn into the storm helping keep the storm from intensifying much.

Dry air (orange) being drawn into the storm helping keep the storm from intensifying much.

I will keep an eye on this storm but do not expect any major impacts on the area.

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