12:45 PM | *Severe storm threat later today/tonight and it’ll continue into Friday when much cooler air arrives…the latest on a more active Atlantic Basin tropical scene*
Paul Dorian
A much cooler air mass arrives in the Mid-Atlantic region on Friday and temperatures should remain below-normal on Saturday and Sunday as well; courtesy NOAA, tropicaltidbits.com
Overview
There is a much cooler air mass headed this way for Friday, Saturday and Sunday and it’ll be an active stretch of weather in the Mid-Atlantic as we make that transition from today’s heat and humidity to the weekend comfort. There is a threat for strong-to-severe thunderstorms later today and tonight in the Mid-Atlantic region and northeast US as a surface low pressure trough will combine with high humidity and upper-level energy to destabilize the atmosphere later in the day. The threat for showers and thunderstorms will continue from Thursday/Thursday night into Friday as a strong cool front only slowly grinds its way through the region. Elsewhere, a minimal tropical storm (Chantal) has formed out over the open Atlantic Ocean and is no threat to the US; however, another system now near the Bahamas will have to be closely monitored in the coming week or so.
A wave of energy aloft will combine with a surface low pressure trough to destabilize the atmosphere later today and this should result in scattered showers and storms some of which can become strong-to-severe; courtesy NOAA, tropicaltidbits.com
Storm threat and transition to much cooler conditions
There is a chance for some strong-to-severe thunderstorm activity to form later today in the NE US and Mid-Atlantic region; especially, north of the PA/MD border as a wave of energy aloft combines with surface low pressure and high humidity to destabilize the atmosphere. As in recent days, the showers and thunderstorms that form are likely to be scattered, but any one of these can produce heavy rainfall and potentially result in damaging wind gusts and hail. As a strong cool front advances our way on Thursday, the threat for showers and thunderstorms will continue as will the very warm and humid conditions - but just for one last day. Any shower or storm that forms later tomorrow and tomorrow night can again result in heavy rainfall.
Some instability may continue early this weekend in the Mid-Atlantic as upper-level energy swings through the region; courtesy NOAA, tropicaltidbits.com
Much cooler air will arrive in the I-95 corridor on Friday and high temperatures could actually be confined to the 70’s in places such as the Philly and NYC metro regions. It will, however, also remain quite unsettled as the surface cool front will be slow to push through the area and this will result in a continuing threat of showers and thunderstorms. In fact, with more upper-level energy aloft on Saturday, a few more showers and thunderstorms cannot be ruled out in the Mid-Atlantic region to start the weekend, but temperatures and humidity levels will be quite comfortable. Those comfortable conditions will continue on Sunday and Monday as well and the chances for rain will diminish on those days as strong high pressure builds into New England.
The latest infrared satellite image of the Atlantic Basin showers a weak tropical storm (Chantal) and an area of interest near the Bahamas (circled, lower left). TS Chantal is no threat to the US, but the disturbance near the Bahamas will have to be monitored in coming days as it meanders over very warm waters. Image courtesy NOAA, CIMSS/University of Wisconsin
Tropical Update
The quiet stretch of weather in the tropical Atlantic that extended from mid-July to yesterday was the first such with zero named storms since 1982…that quite stretch has ended with the naming (Chantal) of a (weak) tropical storm out in the open waters of the North Atlantic. This system is no threat to the US and is moving fairly rapidly to the east into an area of cooler water.
Warmer-than-normal conditions prevail in the western Atlantic Ocean and this is favorable for tropical storm formation and intensification; map courtesy NOAA, tropicaltidbits.com
There is, however, an area of interest currently near the Bahamas that bears watching over the next week or so. This area of showers and thunderstorms will slowly meander off the east coast in coming days in an area where sea surface temperatures are generally warmer-than-normal. In addition to the warm waters off the east coast, another favorable factor for development may be strong high pressure that builds into New England/southeastern Canada during the next week or so as this is quite often a harbinger of more tropical activity in the western Atlantic.
Stay tuned.
Meteorologist Paul Dorian
Perspecta, Inc.
perspectaweather.com
Video discussion which focuses on today’s strong-to-severe thunderstorm threat and the more active tropical scene in the Atlantic Basin :