Hurricane Zeta?

The Hurricane Season of 2005 refuses to quit. Tropical Storm Zeta has not changed much since yesterday, but the forecast for its future has changed considerably. Zeta may become a hurricane by tomorrow. The upper-level trough approaching Zeta is splitting in two, leaving a area of low wind shear just in front of the storm. Wind shear analysis from the University of Wisconsin shows that Zeta's westward motion is carrying the storm into an area of low wind shear less than 10 knots, and this reduced wind shear has the potential to allow Zeta to intensify into a hurricane, something the GFDL model has been consistently predicting for three days.

The reduced wind shear also means that Zeta will hang around much longer than previously thought. A trough of low pressure just to Zeta's west is expected to turn the storm northwards tomorrow, but this trough will probably not be strong enough to completely recurve the storm. Zeta will have to wait for the next trough late in the week before finally recurving and dissipating. During that period, Zeta may reach hurricane intensity for a day or so before increasing shear knocks it back down to a tropical storm.

Long-term tropical storm outlook for January
Today's model runs are now suggesting that a non-tropical low pressure system will form off the coast of Africa on Sunday, in a location similar but a little farther east of where Delta, Epsilon, and Zeta all formed. It is possible that this low could make the transition to a tropical storm early next week. However, the cooler water temperatures in this low's more easterly location will probably keep it from forming into a tropical storm.


Figure 1. Tropical Storm Zeta as seen by the polar-orbiting Terra satellite. Image courtesy of the Navy Research Lab.

Tomorrow: More on Zeta, and the Texas/Oklahoma drought.

Jeff Masters