El Niño Watch issued by NOAA; Western Caribbean development next week?
NOAA's Climate Prediction Center issued an El Niño Watch yesterday, saying "that conditions are favorable for a transition from neutral to El Niño conditions during June - August 2009". The pattern of changes in surface winds, upper-level winds, sea surface temperatures, and deeper water heat content are all consistent with what has been observed during previous developing El Niños. As I discussed in detail in last Friday's post, most of our more advanced El Niño computer models are predicting a weak El Niño event for the coming Atlantic hurricane season. If this indeed occurs, it is likely that Atlantic hurricane activity will be suppressed due to the strong upper-level winds an El Niño usually brings to the tropical Atlantic, creating high wind shear that tears hurricanes apart.
Figure 1. Departure from average of the heat content of the upper 300 meters of the ocean in the Equatorial Eastern Pacific. Much of this increase in heat content is due to a large area of waters 2 - 4°C warmer than average at the thermocline (a depth of 50 - 150 meters). The heat content of the ocean has been steadily increasing since January, consistent with a developing El Niño episode. Image credit: NOAA's Climate Prediciton Center.
Western Caribbean development possible next week
An area of disturbed weather has developed over Central America and the adjacent waters of the Eastern Pacific and Western Caribbean, associated with a tropical wave interacting with the Intertropical Convergence Zone (ITCZ) in the Eastern Pacific. This disturbance has generated 1 - 2 inches of rain over Costa Rica and western Panama over the past day, and is likely to bring 4 - 6 more inches of rain to those areas and Nicaragua over the next 3 - 4 days, as the storm drifts northwards into the Western Caribbean. The subtropical jet stream, which is currently bringing high wind shear to the Caribbean, is expected to shift northwards next week, bringing low wind shear to the region. The last few runs of several of our major dynamical computer weather forecast models have been pointing to the possible development of a tropical depression southwest of Jamaica by Thursday of next week. Heavy rains from the disturbance should spread into Jamaica and Cuba by Thursday and Friday, and may affect the Bahamas, Haiti, and South Florida 7 - 8 days from now.
Figure 2. Visible satellite image of the Central American disturbance expected to cross over into the Western Caribbean next week.
I'll have an update this weekend, probably on Sunday.