Tropical Depression Ten (2007): brief Gulf Coast system

Formation and development

The disturbance began as a subtropical feature on September 21, classified initially as a subtropical depression. Its genesis was the result of interaction among a tropical wave, the trailing end of a cold front, and an existing low pressure system over the northeastern Gulf of Mexico. Early observations noted a rather disorganized circulation and scattered thunderstorm activity, but over a short period the convective activity became better concentrated around the center, allowing the system to be reclassified as a tropical depression once sustained convection persisted near the low-level circulation.

Track, landfall and dissipation

The depression tracked generally northwestward toward the Florida panhandle. It made landfall near Fort Walton Beach early on September 22 and weakened quickly over land, degenerating into a remnant low and dissipating over southeastern Alabama later the same day. Because of its brief life span and limited organization, the system did not attain tropical storm strength.

Impacts

Impacts along the coast and inland were modest. Rainfall associated with the depression was generally light, and reported structural or wind damage was limited. However, the broader weather system that spawned the depression produced at least one notable severe weather event: a damaging tornado struck the area around Eustis, Florida, illustrating that even weak tropical or subtropical cyclones can be accompanied by localized severe storms.

Characteristics and distinctions

Some characteristics of Tropical Depression Ten that are useful for understanding similar systems include its subtropical origin, rapid tropical transition, and quick inland decay. Subtropical depressions typically have a broader wind field and less centralized deep convection than purely tropical depressions, but processes such as increased central convection can convert a subtropical system into a tropical one. Short-lived Gulf-origin depressions often pose forecasting challenges because small changes in organization or track determine whether they remain at sea or make landfall.

Quick facts

• Designation: Tenth tropical cyclone of the 2007 season.
• Initial classification: Subtropical depression on September 21.
• Key contributors to genesis: tropical wave, cold front, and an existing low pressure system.
• Landfall: near Fort Walton Beach, moved northwestward into southeastern Alabama.
• Associated hazards: light coastal rainfall, localized severe weather including a tornado in Eustis.

Though minor compared with named storms, Tropical Depression Ten (2007) is an example of how rapidly evolving low-pressure systems in the Gulf can affect coastal and inland areas. Meteorologists monitoring similar disturbances use satellite imagery, surface observations and convection trends to assess whether a subtropical feature may acquire enough organization to be classified as a tropical depression or storm, and to evaluate associated threats of rain, wind, and tornadoes.