Coastal storm this week, possibly Joaquin?

Good evening.

It’s been fairly quiet weather-wise in the Northeast recently, but that is about to change. A new weak coastal low, which has been tagged as Invest 97L, is currently located off the Carolina coast, with a pressure of about 1010 mb. There is a chance it may develop into a tropical or subtropical cyclone, which would be named Joaquin if it reaches storm status. The NHC has the probability at only 10% presently, but given the warm water, baroclinic assistance and deep convection, I would estimate the chance to be greater. The conditions are marginal for development, but many systems have developed in that region with similar setups. Regardless of development, it will be a weather maker for days to come.

Track and Synoptic Forecast

Given the relatively static weather pattern in place in the region with a ridge of high pressure to the north, most likely this low is not going very far in the short term. It looks to meander off the east coast as it is trapped between ridge axes, with only a very weak trough into the eastern Gulf of Mexico providing any backing. The ridge will only strengthen in the days ahead, which will prevent any northward movement. Only by the weekend or early next week will the low be able to move out of the region, as the ridge slowly weakens and a new trough is expected to push into the region. Given the fact the system has nowhere to go but slowly westward or meander (it may make landfall, most likely in North Carolina, during that time) the track confidence is High.

Atmosphere profile at the 500 mb level. Notice the ridge to the north and east, likely to act to block the system.

Atmosphere profile at the 500 mb level. Notice the ridge to the north and east, likely to act to block the system.

gfs_mslpa_us_10

Surface pressure forecast as of Thursday night. Notice the anomalous ridge to the north.

Conditions are marginal for intensification, and no model develops the low into more than a weak subtropical or tropical storm. Many models even dissipate the low center, leaving a disorganized trough axis the entire week. Wind shear is fairly high, but the trough axis may act as a shield and create some baroclinic influence. Even if this system develops, it would most likely be a subtropical or hybrid system with some extratropical characteristics. One possible analog might be Tropical Storm Danielle of 1992. Confidence in the intensity is Moderate.

Northeast Impacts

The ridge to the north should keep impacts to a relative minimum in the northeast, at least on land. Heavy rain is likely at times in the coastal Carolinas (the Outer Banks could see 6 to 9 inches of rain by the weekend), but little or no rain is expected in the Northeast until early next week, and even then only showers are likely. Winds may be breezy (or locally gusty depending on the strength of the pressure gradient) but nothing too serious. Overall, this system is not expected to be a significant issue inland.

It is a different story at sea, though. Look at the tweet posted this afternoon – by the weekend, south of New England could see wave heights as high as 15 to 25 feet as the system continues to stir up the ocean. Some coastal erosion is certainly possible, especially from Long Island southward to the Delmarva coast. Those looking for a weekend getaway to the beaches might seriously want to think twice about their plans.

Conclusion

While it may be an El Nino year and the tropics have been quiet for the most part, this is a reminder that hurricane season is still at its peak. There is some chance that this might become a named storm (Joaquin) but regardless, the impacts will be the same. It shouldn’t be much of a problem on land, but the beaches and at sea it is a completely different story. Given the weak steering currents, this will be with us for a while to come too.

Forecaster Craig Ceecee

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