Double Dose of Tropical Action in the Atlantic?
Danny really got its act together this morning, forming an eye and strengthening into a hurricane well to the east of the Lesser Antilles. However, it is not the only game in town – there is a second low pressure area developing much closer to home. (There is also a third system in the far eastern Atlantic, but it will not be mentioned much here.) The second system, which will be explained below, is worth watching and is important in that it could also play a role in Danny’s future – if it survives long enough.
Non-tropical low near Bermuda
There is currently a developing upper-level low pressure area and a surface trough to the west of Bermuda and southeast of Cape Hatteras. It is expected to fully develop by Saturday at the latest, possibly as early as tomorrow, and likely combine with the remnants of a cold front moving across the Northeast and weakening. Most models show the low being “cut off” from the jet stream and possibly taking tropical or subtropical characteristics this weekend into early next week. The NHC has given it a 20% chance of such development in the next 48 hours (by Saturday afternoon) and a 60% chance within 5 days (by Tuesday). If it does develop, it would be named Erika, the next name on the list.
Mid-latitude cutoff lows in the summer tend to be notoriously erratic in track, and this would likely be no exception, as steering currents would likely be weak with the low cut off from the jet stream. Ultimately, most models rebuild the subtropical ridge to the south, while locking it in to the east. As a result, it should meander around the northwest Atlantic, possibly coming close to the Northeast coast. Model tendency is to keep it weak, given the marginal conditions. It is worth watching, however.
Confidence in track/genesis: Low to Moderate. Confidence in intensity: Very Low.
Much farther away, Danny is now a Category 1 hurricane, the first of the season, as it intensified quite significantly this morning. It is small enough with a strong circulation that it might be able to intensify more, but the dry air plaguing Danny has not disappeared. As a result, quick weakening is certainly a possibility as much as rapid intensification to a significant hurricane is also a possibility with convective bursts. Sustained winds are currently 75 mph.
Models are in good agreement that Danny is headed westward towards the Leeward Islands, and then either near or just north of Hispaniola and Puerto Rico. If it misses the large islands or survives that long, the track forecast becomes more uncertain and dependent on the Bermuda low. If it is still hanging around and the ridge does not rebuild, a window of opportunity for recurving will exist and Danny (or its remnants) could head out to sea. However, if the ridge rebuilds, the most likely path is westward, either towards Florida, into the Florida Straits or through the Greater Antilles. That is, however, several days away.
Intensity is also tricky. In the short term, convective bursts and dry air should dictate the intensity as long as the core remains intact. Periods of rapid weakening and rapid intensification are possible. By the weekend, shear is expected to increase, which should weaken Danny greatly as it nears and passes through the Leeward Islands. Most models weaken Danny to a weak tropical storm or even dissipate it over that time frame. Given its small size, quick dissipation is certainly not out of the question. Shear decreases north and northwest of the islands, but what kind of system would be left?
Confidence in track: Moderate to High. Confidence in intensity: Low to Moderate.
As you can see, a busy stretch is ongoing, and one of the systems might have a bearing on our weather. It is unlikely to be a major storm, but we should keep a close eye on the tropics regardless.
Forecaster Craig Ceecee (@EternalWeather1)