It's possible that the @NOAA_HurrHunter aircraft just measured the first solid evidence of vertical shear directly attacking the eyewall of Hurricane #Isaias. The last penetration measured an anomalous temperature spike at 750mb within the SW eyewall -—not within the eye—7C higher than the previously measured eye maximum. This might be evidence of a rapidly descending flow belt caused by shear laterally forcing external air into the eyewall region, leading to a massive subsidence inversion. This is often observed in high-resolution modeling (see HAFS sounding from this morning's 06Z run). The dewpoint also sharply decreased concurrent with the temperature spike measured by aircraft, supporting the possibility that this phenomenon was observed. This could foretell significant erosion of the southern eyewall in the near future, but time will tell. For now, Isaias remains as strong as ever according to the same aircraft data.

We are monitoring a tropical disturbance in the Bay of Campeche near the tail-end of a Gulf Coast cold front that could end up impacting Gulf states in a few days. While poorly organized right now, thunderstorm activity is increasing, and this system has a chance to develop into a tropical storm later this week. Environmental conditions won't be a slam dunk here. The cold front is associated with the upper-level jet stream, causing strong wind shear along the Gulf Coast that disfavors an organizing storm. However, the position of a series of shortwave troughs over Texas through ~Friday also facilitates strong upper-level divergence over the Gulf near a jet streak entrance region, which could help the disturbance fight off the wind shear a bit. Computer models are splitting into two broad camps: 1. Most AI-based models (see AIFS example) show the system moving northeast more quickly, prior to the Texas shortwave trough lifting out. This would place the storm in the most favorable position to intensify, and would bring it into the central or eastern Gulf Coast by the weekend. 2. Several physics-based models (see ECMWF example) are slower to lift the disturbance northward, allowing the Texas shortwave to exit and the favorable jet dynamics to subside, giving way to a more purely hostile environment for a potential tropical storm. The result is a weaker, messier storm that waits until next week to attempt a move toward the Gulf Coast, if ever. Significant uncertainty remains in this scenario, but this disturbance is one to watch this week. Even if a strong storm is avoided, heavy rains may stay in the forecast for portions of the Gulf Coast. Keep an eye on the forecast from the National Hurricane Center, which currently gives a 70% chance of a tropical cyclone forming.