Invest 91 not expected to develop; wild June weather continues

A tropical wave approaching the coast of South America near the southernmost Lesser Antilles Islands has developed some spin and a bit a heavy thunderstorm activity. This disturbance has been labeled Invest 91 by NHC this morning, but does not appear to be a threat to develop into a tropical depression. Water temperatures are warm enough and shear is low enough to allow some development, but dry air on the west side of the disturbance is limiting its thunderstorm activity. The disturbance should move ashore over South America by Thursday before a tropical depression can form.

Wind shear is very high over the Caribbean, and is expected to remain high for the coming week. None of the computer models are forecasting tropical development in the coming week. However, wind shear is forecast to be low along the northern coast of South America and in the waters offshore of Panama and Coast Rica. We will need to watch this area for development early next week when the moisture from Invest 91 arrives.

Wild June weather across the U.S.
It's good to be back blogging again! I had a great week of relaxing and recharging in the Bitteroot Mountains of Montana the past week. It was pretty nuts to go for a hike yesterday--35° with heavy snow and driving wind--then come back to the sweltering east with the vegetation going bonkers from all the heavy rain of the past week. An unusually pronounced kink in the jet stream is responsible, which allows cold air to spill southward over the Western U.S., while at the same time pumping plenty of hot, moist air northwards into the Eastern U.S. The latest 2-week forecast from the GFS model indicates a continuation of a more active than usual jet stream the remainder of June, so expect plenty more wild weather this month. The main action today will be in Iowa, Nebraska, and eastern Kansas, which the Storm Prediction Center has placed at "Moderate" risk of severe weather.

Jeff Masters