The Atlantic’s first “Invest” – short for area of investigation – was designated early Sunday morning. Invest 90L is currently producing disorganized shower activity well east of the Bahamas, but a narrow window for potential tropical or subtropical development exists between late Monday and Tuesday. If 90L becomes a tropical or subtropical storm, it will be named Andrea.

As of 00:00 UTC Monday, Invest 90L was centered near 26.0°N 66.8°W. Maximum sustained winds were 20 knots (25 mph), with an estimated minimum pressure of 1012 mb. The National Hurricane Center (NHC) gives 90L a 50 percent chance of development, both within 48 hours and five days. An Air Force Hurricane Hunter aircraft is scheduled to investigate 90L tomorrow, if deemed necessary. If 90L does not organize significantly, it is possible the flight may be canceled tomorrow morning.

90L has become slightly better organized today, but still has a long ways to go before being classified as a tropical or subtropical cyclone. Sea surface temperatures are expected to be marginal for tropical cyclogenesis for the next 36 hours or so (above 24°C/75.2°F), and although the vertical wind shear analyzed over the system is estimated to be over 30 knots (35 mph), the shear is highly divergent, which has less of a suppressing effect on cyclogenesis. The mid-level atmosphere is fairly moist but not overwhelmingly so, with the mid-level relative humidity values expected to remain near 60 percent for the next 36 hours or so. After 36 hours, sea surface temperatures cool, and the wind shear increases significantly, making conditions very hostile for further development. If 90L does develop into a subtropical or tropical cyclone, it will be weak and short-lived. If it develops and acquires maximum sustained winds of at least 34 knots (39 mph), it will be named Andrea. Interests in Bermuda should continue monitoring the progress of this system, though I do not think any significant effects are likely at this time.

In the eastern Pacific, Invest 91E has become less organized today, and NHC has lowered the development chances within 48 hours to near zero percent and the five-day chances to 20 percent. NHC has also stopped, at least temporarily, issuing automated tropical cyclone forecast (ATCF) system updates on 91E. Global models have also backed off any development of 91E in the short term. If 91E becomes a tropical storm it will be named Alvin.