There are two disturbances that are being watched in the Atlantic that could gain some tropical characteristics and become subtropical depressions or storms. Neither feature are anywhere near developing a true warm-core structure from the surface to 500 MB, but a subtropical development with a warm core up to 850 MB is certainly possible over the next 24 to 66 hours.
The first disturbance is well to the east of Bermuda with convection attempting to form around a low-level center of circulation. The water vapor satellite clearly features dry air wrapping in from the southwest side of the upper-level structure with a modified Polar air mass, but there are indications of a low-level warm-core circulation as convection attempts to form around the low-level center. A strong cold front moving off the east coast by tomorrow will entrain this feature by Tuesday night with strong vertical wind shear increasing tonight. As a result, the amount of time left for this disturbance to develop is coming to a close.
The second disturbance is being monitored just north of Puerto Rico. This disturbance was actually a shortwave in the Subtropical jet stream over the Tennessee River Valley at the start of last week. Since then, the disturbance has drifted to the south of Hispaniola and now has lifted back north over Puerto Rico. The disturbance is currently an extratropical disturbance but could pick up some tropical characteristics as a Subtropical disturbance while drifting back towards the United States, specifically Florida. Overall this disturbance is expected to mature as a broad low-pressure system with a clear upper-level low-pressure system, but a warm core below 850 MB could develop while drifting over the Bahamas this week. The disturbance is expected to produce widespread rainfall initially over Florida by Wednesday and then be drawn northward into the Northern Mid-Atlantic by Friday night through Saturday morning.
