Jeff co-founded the Weather Underground in 1995 while working on his Ph.D. He flew with the NOAA Hurricane Hunters from 1986-1990.
By: Dr. Jeff Masters , 2:08 PM GMT on October 14, 2005
A broad 1006 mb low pressure area is centered just south of Jamaica this morning, and is a definite threat to develop into a tropical depression over the next few days. Some impressive thunderstorms have developed to the south of Jamaica this morning, and the general organization of this system has improved since yesterday. This is largely due to the fact that wind shear overhead has dropped from 15 knots yesterday to 10 knots today. No upper level outflow or low-level spiral banding is apparent on satellite imagery yet.
Global computer models forecast that the shear will continue to decrease over the area Saturday and Sunday, and I think it is 70% likely by Monday that a tropical depression will form. Steering currents are very weak, and the disturbance is expected to stay in the central or western Caribbean for at least the next five days. This is a set-up typical of what we've seen in the past for the formation of late-October hurricanes. It would be no surprise if this system ended up becoming a hurricane five to seven days from now. Water temperatures are still very high--up to 32 C near Jamaica--so the ocean can even support a major hurricane, although this is rare in late October.
The eventual track of any tropical storm or hurricane that forms is impossible to forecast with any reliability, since steering currents are very weak and a some erratic motion is likely. The various computer models either keep the storm in the Caribbean the next seven days, or move it northeast across Cuba and the Bahamas, or move it west or southwest across Central America or Mexico's Yucatan. In other words, anything can happen.
Figure 1. Current Sea Surface Temperatures compiled by NOAA's AOML.
Cape Verdes tropical disturbance
A tropical disturbance about 500 miles southwest of the Cape Verde Islands continues to slowly improve in organization. Visibile satellite imagery and QuikSCAT satellite winds suggest that a surface circulation may be forming here, and some modest upper-level outflow has developed to the north. The system is headed towards an area of low wind shear, which may allow some further development over the next few days as it tracks west-northwest over the open ocean. Tropical storms developing this far east in mid-October are very rarely a threat to the Caribbean or North America.
New England continues to suffer the onslaught of a very wet stream of tropical air from the southeast that has caused nine straight days of rain. The axis of moisture has shifted slightly eastwards today, finally giving New York City a break from the 6 - 8 inches of rain that has fallen the past two days alone. This tropical onslaught will continue moving northeast over the weekend before exiting northern Maine on Sunday.
Figure 2. Lots of rain in the Northeast the past week, but currently just a few areas of major river flooding, in New Jersey.
I'll have an update this afternoon around 3pm, and follow-up then on my post yesterday about Katrina's winds.
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