By now, the majority of you have probably heard about the possibility of a tropical/sub-tropical system developing off the East Coast next week. It’s not uncommon to have a pre-season tropical system to develop, and it doesn’t necessarily mean that pre-season activity is a sign that the upcoming season is going to be active. However, just because a tropical or sub-tropical system develops early doesn’t mean it can’t bring heavy rain, higher surf, and strong winds just like during the normal Atlantic hurricane season (June 1st – November 30th).
A frontal boundary pushed past Florida the other day, bringing the area heavy rainfall, and now this old boundary has stalled below the state across the western Atlantic. You’ve heard me talk a lot about the active sub-tropical jet stream over the past few months, which is a column of strong winds in the upper-levels of the atmosphere and has been responsible for transporting a lot of moisture into parts of the United States this spring. That’s why many of you have been inundated with heavy rain this season.
In fact, this active jet stream is currently stretching across the entire Atlantic and into Europe, bringing many areas around the world wetter conditions. This sub-tropical jet stream is going to carry over a piece of energy across the Gulf that will eventually be responsible for triggering the development of a surface low pressure system along that stalled front in the western Atlantic/along the southern East Coast. This is the system to watch!
It’s difficult to determine if this system will be fully tropical or sub-tropical, but the overall impacts should be about the same regardless. A sub-tropical system has the characteristics of a tropical system (e.g. tropical storm, hurricane) and a mid-latitude cyclone (e.g. a low pressure system with an associated cold front, warm front, etc.). I’m not going to take the time to get into any more detail on the differences between the two.
Once this low pressure system develops, it could strengthen as it slowly moves northward along the southern East Coast. A trough is currently moving off the East Coast (which has been responsible for the nicer/cooler weather for many), and a ridge (blocking high pressure) is going to build over much of the United States in its place. Since this is going to happen, our storm is not going to be able to go anywhere and will be suppressed to the south. This means it will likely meander off or along the coast for several days until it gets pulled farther north.
The sea surface temperatures in the Gulf of Mexico and along the East Coast are above average, and there is a tongue of warmer waters along the East Coast being pulled up from the Gulf stream. This could give this system the needed fuel to strengthen into the first named storm of the Atlantic hurricane season. That’s very uncertain at this point though.
What To Expect:
This storm needs to track fairly close to the coast to have a decent chance of strengthening. The areas that will most likely be impacted with heavy rainfall and gusty winds will be from the Florida east coast up through South Carolina/North Carolina. Again, this storm will probably just sit along or over these regions for several days next week, and eventually a trough should move far enough east (maybe next weekend) to pull the storm farther up the coast, bringing heavy rain farther north along the coast.
As always, have a plan in place just in case. Although it’s early in the year, rapid strengthening can occur, and it’s definitely not impossible. Right now, it’s much too early for me to try to forecast actual strength, but I wouldn’t be surprised if this ends up being a decent tropical/sub-tropical system, which would be named Ana. Remember that forecasting the strength and exact track of a tropical system is difficult in meteorology, which is why you should always be prepared.
I’ll continue to keep everyone updated in the coming days.