Tropical Storm Debby: Debby made landfall during the overnight hours of last night about 25 miles to the northeast of Charleston.
It is expected that Debby will travel across Virginia, Maryland and central Pennsylvania as we get into tonight and Friday morning. By Friday night, the remnants of Debby will travel across central and northeastern New York State before moving into eastern Canada by Saturday.
The risk for heavy rain with flash flooding is expected to continue in an area from north-central North Carolina through central Virginia the rest of today into Friday. This heavy rain and flood threat will then spread into an area from northern Virginia through central Pennsylvania, central and northeast New York State and northern Vermont during Friday and Friday night.
In addition to the heavy rain, a risk for severe weather with isolated tornadoes will continue to be a threat through tonight across the Mid-Atlantic states. This severe weather threat with isolated tornadoes will then spread northward during Friday and Friday night into eastern Pennsylvania, a large part of New Jersey, eastern and southeastern New York State and western parts of Southern New England.
This will be the last update on Debby.
Area Of Disturbed Weather Over The Eastern Tropical Atlantic: An area of disturbed weather now located over the eastern Tropical Atlantic near about 33 West Longitude has a really high chance of developing by early next week as it’s approaching the area around the northeastern Caribbean.
Over the next few days, the environmental conditions are going to be marginally favorable, at best, for development. This is mainly due to quite a bit in the way of dry air present over the central and eastern Tropical Atlantic. Because of this, slow to very slow development seems likely right through this weekend and in fact, it may not be until Sunday or more likely Monday when we may start seeing development from this disturbance.
By early next week, this disturbance looks to find itself in a more favorable environment and because of this development looks to occur as its moving over the Leeward Islands into the northeastern Caribbean. Because of this, I urge interests in the Leeward Islands, Virgin Islands, Puerto Rico and Hispaniola to closely monitor the progress of this disturbance as at the minimum it could bring you very squally weather Monday and Tuesday.
Beyond this, the forecast becomes very uncertain due to the evolving upper level weather pattern. An upper level trough of low pressure is expected to be in place near the northeastern United States with an upper level high pressure system located from eastern Canada to near Bermuda. The question then becomes where exactly this upper level trough be and how strong will it be.
On one hand, a stronger upper level trough would probably pull this system sufficiently to the north and guide it safely east of the Bahamas and the US coastline, although, Bermuda could be threatened.
On the other hand, if that upper level high pressure beats back that upper level trough or even undercuts the trough, it could lead to a very different scenario including a track that takes this system into the Bahamas and then either right up the US East Coast or even into the Gulf of Mexico.
Here Are My Thoughts: I don’t think that we’re going to see this disturbance track safely away and I do think that it’ll probably try to fight its way westward towards the Bahamas and some portion of the US coastline around the August 16-18 time frame.
The steering setup for the middle and later parts of next week are going to be very similar to what we just saw with Debby when it approached the southeastern Bahamas. If you remember, model guidance initially had Debby moving east of the United States too and I suspect we might be seeing the same model bias with this disturbance.
This opens up two equally as possible scenarios:
The first is for this disturbance to be a hurricane as it rides up the entire US East Coast between August 16 and August 18. In this first scenario, the further up the East Coast you are, the higher the chance there is for a direct impact given the ridge/trough setup.
A second scenario is for that high pressure ridge to undercut the trough causing this system to be steered westward similar to Debby taking it into the eastern Gulf of Mexico and towards the northern Gulf Coast around August 18-19 or so.
Needless to say, this is a disturbance that definitely needs to be watched very closely in the coming days.
Looking beyond this disturbance, the model guidance are now strongly signaling a definite increase in activity with some guidance pointing towards the possibility of 2 to 3 more areas to really watch by late next week. It definitely looks like we are now starting the very active part of the season and the light switch is now being flipped on for about the next 8 weeks or so.
The next tropical weather discussion will be issued on Saturday.