July 17: T-storm & Heat Discussion

Jonathan Carr
By Jonathan Carr July 17, 2019 12:16

July 17: T-storm & Heat Discussion

Discussion: The first order of business is tonight’s thunderstorm potential. So yes this is remnant energy leftover from Barry that dissipated over the N Gulf Coast and made it’s way through Arkansas, parts of Missouri, Kentucky, etc. and will now move through NJ tonight. We’re not “getting hit by Barry” though. That seems like a click-bait stretch headline. It’s just remnant energy that functions and behaves like other atmospheric lifting, condensation and dynamics.

I’ve been looking at the instability and wind shear profiles on soundings and I’m not seeing anything crazy. What’s jumping out at me are the very high surface dew point temperatures and a trigger. The dews are self-explanatory. It feels like someone slapped you in the face with a steaming towel when you walk outside. Because of this moisture-rich environment PWAT values are near 2 inches. That’s a lot of potential rain that can fall. This hot and moist surface setup is pure thunderstorm fuel by itself but you still need ignition via lifting. Instability isn’t lift though. Instability is the result of hotter surface air producing negative buoyancy. Hotter air is thinner and moves easier than colder air—therefore it rises easier. Shear can provide lift if enough rolling occurs from different winds at different altitudes. With the upper-jet being so far northward we’re not dealing with alarming shear. I’d say the shear is just marginally sufficient to possibly aid in the sustainment of thunderstorms not the development of.

Again, it’s the trigger that is jumping out at me in conjuction with the dew points. The trigger in this case is a weak low pressure center that should move through NJ between about 8pm and midnight tonight. This low is the result of colliding air, under the Barry remnant lifting, caught up in the coriolis effect. The lifting from this trigger is enough to hoist the ridiculous humidity high enough for condensation and thunderstorm development. It’s also enough to elevate shear at the mesoscale/microscale level enough for tornado formation. Therefore I see strong-to-severe thunderstorms tonight in that 8pm-midnight period moving from WNJ to ENJ. At this point in time NNJ/CNJ look to get hit harder than SNJ but that’s just model guidance. Let’s use our heads and realize that there is thunderstorm fuel statewide with a passing trigger that could drift N or S of the expected CNJ bulls eye. Everything should clear out after midnight tonight. Tomorrow we should see an okay day (not too-too hot) but then the worst of the heat begins for Friday through Sunday possibly into Monday.

The upper-jet is way to our N through Canada (we know that). Between Friday and Monday the upper-level ridge will flex over the Mid-Atlantic and NorthEast US. It’s a relatively flat ridge but it will flex enough to produce likely the hottest conditions of the year. All of NJ, with the exception of the highest NNJ elevations and immediate SENJ coast, should flirt with breaking 100 degrees on each day of the heat wave. Dew points should be 70+ for most areas making it feel like 110+. NNJ elevations and immediate coastal areas might hang in the 90s and cool off quicker for evening hours (especially with any sea breeze front mechanism creation). The sea breeze front is very possible given the upper-level westerly flow that could assist the sea breeze front cycle (rising air inland…sinking air offshore…all assisting E flow at the surface). I doubt any relief will make it much further inland than the barrier island regions however.

The most important aspect of the heat this weekend is safety! Make sure you stay as hydrated and cool as possible. A recommendation is at least 64-80 ounces of water per day. If you have to work outside then take breaks in the shade. Please consider checking on your pets and elders more frequently during this heat wave. Know the difference between heat exhaustion vs heat stroke. By Monday-Tuesday we should have a cold front (possibly stormy) roll through and cool things off at least temporarily. I’ll cover all this more in tomorrow evening’s weekend outlook.

In English: Strong to severe thunderstorms are possible tonight. Storm action should approach WNJ around 8PM and clear ENJ by midnight-ish. Expect heavy rainfall (flash flooding possible), frequent lightning and possibly damaging winds and maybe even some tornadic activity (we’ll see). The NNJ/CNJ border area (near I-78) is currently targeted for the strongest thunderstorm action with extreme NWNJ and SENJ a little less favored. Let’s all have our guards up just in-case. After all there’s thunderstorm fuel everywhere today and we all know the best dynamics can drift slightly N or S. As for the heat it will be hazy hot and humid Friday through Sunday possibly into Monday. We’re talking life-threatening heat especially along the urban I-95 corridor and surrounding areas rich in concrete/pavement. Please stay as hydrated and cool as possible and check on your elders and pets. Everyone have a great rest of your Wednesday. I’ll check in tonight when the thunderstorms are approaching. Be safe! JC

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Jonathan Carr
By Jonathan Carr July 17, 2019 12:16