All eyes have been on the Gulf this week with Francine now expected to make landfall in Louisiana Wednesday. The track over the last several days has been trending east! This means we will feel less impacts here on the clean side of the storm.
Why is Francine heading east? It’s because of a high pressure system in Florida! High pressure systems rotate clockwise in the Northern Hemisphere, where we live. These highs are large, synoptic scale features that influence the weather pattern across thousands of miles. Highs act as a blocking system, and lows (tropical systems) tend to travel in the path of least resistance. Often the high-pressure systems surrounding a hurricane determine where it will move, and if it can move.
In this case the high pressure system in Florida, it is turning Francine the right. The circulation is pulling it towards Louisiana.
High pressure systems also were the main influencer during Harvey. During Harvey there were several highs that blocked the hurricane from moving, which is why we saw a multi-day flood event. There was nowhere for the low pressure system to move due to highs being located over NW Texas, Michigan, and Coastal Florida.
The location of highs is so important to hurricane forecasts. This is actually what I wrote my senior thesis on during college. Thankfully for Francine the high pressure system is actually what helped keep us mostly dry.