The east Pacific hurricane season does not officially begin until May 15 and the Atlantic season not until June 1. However, that does not mean that the tropics will wait until those dates to start producing interesting weather.
Many of the global computer models are hinting at tropical cyclone development in the southeast Pacific and possibly in the western Caribbean over the next week to 10 days. Water temps are warm enough, no question about that. But will upper level winds and other factors such as dry air be pro or con for development? Let’s take a look.
May 10-20 Points of Origin Map (graphic 1)
First, how about climatology. If we look at the points of origin for tropical cyclones from May 10-20 (graphic 1) we see that both basins have almost the same number of developments 9 for the Pacific, 8 for the Atlantic. So it is possible to see development in both regions during this upcoming time period. This also makes me wonder why the east Pacific starts on May 15 and the Atlantic does not. They both seem to have the same chances for development from this date forward. Interesting, but not for me to decide.
Caribbean Sea Vertical Instability Graph
Next, let’s look at the vertical instability for the Caribbean right now. Granted this is the current pattern, but it will give us an idea of whether or not the mid-levels of the atmosphere are too dry. As we can see, the vertical instability is currently running just a tad above climatological levels, meaning that the air is nice and buoyant or unstable. This is important because a stable, drier environment, like we saw for almost the entire hurricane season last year in this region, will not allow for tropical cyclone formation or at least keep it weak and disorganized. This is a marked change from last season and something we’ll need to monitor throughout the upcoming season.
GFS 168 Hour 200mb Forecast
Next, upper level winds. The GFS forecasts a fairly nice area of high pressure at the 200mb level in a week. I won’t look beyond a week since too many variables come in to play. But right now, the latest operational run of the GFS shows an area of favorable upper level winds developing over the western Caribbean Sea, extending from the southeast Pacific actually. All we need now is a disturbance of lowering of the surface pressures to set off tropical convection. Will that happen? The various models suggest that it might. I would bet more on the east Pacific than the Caribbean right now, but do not discount entirely the chance of a named storm in the east Pacific followed by the chance of one forming in the western Caribbean Sea before June 1. It’s rare, but it does happen and the region we’ll be watching, according to the climo map in graphic 1, shows that we’re looking in the right place.
So for now, just something to monitor and nothing to be concerned about, not in the least. As things develop, or not, I’ll post more info here and via our Twitter and Facebook pages. Not following us there yet? Click either of the two icons above to join the social media side of HurricaneTrack.