Before I get to the longer-range forecast and its implications for the rest of July, let's look over the details of the shorter-range forecast, and what it means for the next several days.
First and foremost, the Bermuda high is "attempting" to push westward from the Western Atlantic on to the East Coast. At the same time, this Bermuda high is pumping extremely warm and moist tropical air into a large portion of the Eastern United States. Because of this warm, moist, and at times, unstable flow, the mundane pattern of warmth and humidity will continue for at least the next 3-5 days, with the possibility of daily thunderstorm activity in the tropical air mass.
The Bermuda high is being forced westward because of the breakdown of the "split" trough that has been sitting over parts of the East and Midwest for days, bringing heavy showers and thunderstorms at times. This pattern will end soon, giving way to diurnally-driven showers and thunderstorms, and then to a drier pattern in the long-range.
As for now, expect increasing humidity and day-time temperatures in the coming week, with high temperatures averaging around 85-90 with dew points in the low to mid 70's. This will allow for isolated thunderstorms to develop each day in the unstable air mass.
As for the long-range, there is some model disagreement, but the overall consensus is as follows:
1.) The Bermuda High begins to shift back east, and causes the height pattern at 500 millibars to flatten out across the United States.
2.) At the same time, a shortwave ejects from the main Alaskan vortex [which is trying to hold together], and flattens the Western ridge, while sending a surge of warmth eastward [about mid-late next week; possibly allowing temperatures to hit 90].
3.) The shortwave then deepens weak troughing in the far East along Maritime Canada and the East Coast. This causes a re-amplification of the upper level pattern, and causes the ridge out West to strengthen.
4.) By late next week, and the weekend, a secondary stronger wave ejecting from the main Alaskan vortex [and subsequently weakening it as well] will force the ridge to move eastward, and amplify. This will cause mid-level subsidence to strengthen, with compressional heating, daytime clearing, and thus much warmer air temperatures.
At the same time, ridge heights may build as high as 5940 meters or more according to the ECMWF, which could allow 90+ surface temperatures. Even then, the humidity levels will linger, with dew points well above 70 likely.
Even in this case, we still have model disagreement. Some of the ensemble members have a much flatter height pattern in the long-range, and thus, not as warm of surface conditions [but still rather warm]. I will continue to monitor this to see how the models change their forecast in coming days, but I do think its becoming apparent that a much warmer pattern is headed our way for many areas west of the Appalachians.
First and foremost, the Bermuda high is "attempting" to push westward from the Western Atlantic on to the East Coast. At the same time, this Bermuda high is pumping extremely warm and moist tropical air into a large portion of the Eastern United States. Because of this warm, moist, and at times, unstable flow, the mundane pattern of warmth and humidity will continue for at least the next 3-5 days, with the possibility of daily thunderstorm activity in the tropical air mass.
The Bermuda high is being forced westward because of the breakdown of the "split" trough that has been sitting over parts of the East and Midwest for days, bringing heavy showers and thunderstorms at times. This pattern will end soon, giving way to diurnally-driven showers and thunderstorms, and then to a drier pattern in the long-range.
As for now, expect increasing humidity and day-time temperatures in the coming week, with high temperatures averaging around 85-90 with dew points in the low to mid 70's. This will allow for isolated thunderstorms to develop each day in the unstable air mass.
As for the long-range, there is some model disagreement, but the overall consensus is as follows:
1.) The Bermuda High begins to shift back east, and causes the height pattern at 500 millibars to flatten out across the United States.
2.) At the same time, a shortwave ejects from the main Alaskan vortex [which is trying to hold together], and flattens the Western ridge, while sending a surge of warmth eastward [about mid-late next week; possibly allowing temperatures to hit 90].
3.) The shortwave then deepens weak troughing in the far East along Maritime Canada and the East Coast. This causes a re-amplification of the upper level pattern, and causes the ridge out West to strengthen.
4.) By late next week, and the weekend, a secondary stronger wave ejecting from the main Alaskan vortex [and subsequently weakening it as well] will force the ridge to move eastward, and amplify. This will cause mid-level subsidence to strengthen, with compressional heating, daytime clearing, and thus much warmer air temperatures.
At the same time, ridge heights may build as high as 5940 meters or more according to the ECMWF, which could allow 90+ surface temperatures. Even then, the humidity levels will linger, with dew points well above 70 likely.
Even in this case, we still have model disagreement. Some of the ensemble members have a much flatter height pattern in the long-range, and thus, not as warm of surface conditions [but still rather warm]. I will continue to monitor this to see how the models change their forecast in coming days, but I do think its becoming apparent that a much warmer pattern is headed our way for many areas west of the Appalachians.
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| The trend in the PNA index indicates that a warmer pattern is a possibility later next week. |
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