What is a Tropical wave and where do they come from?
Normally a tropical wave starts off as a sand storm in the Sahara Desert. Especially in the summer months there is a significant temperature gradient between the hot desert and the cooler waters along the Gulf of Guinea Coast. So this hot, dust and sand filled wind starts moving west and developing into a trough of low. The wave, now bow shaped, is now being transported by the African Eastern Jet which moves east west across the Atlantic.
A new tropical wave departs western North Africa about every 2-4 days between April and November, with about 60-65 waves per year, on average.
In the Atlantic 85% of all their major hurricanes have their origins traceable to these African waves and about 60% of all tropical storm and cat 1-2 hurricanes are spawned by these waves.
Those that make it across the Atlantic and the Caribbean without tropical development (a tropical storm or hurricane) normally cross Central America and end up in the Eastern Pacific basin where they looking for a low to stimulate in the waters warmer than 80 degrees.
Shown below is the daily SST or Sea Surface Temperature chart. Storms like to be in waters around 26.2 celsius or around 80 degrees ferenheight
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In our tropical kitchen this morning that low that is west of Zihuatanejo, parked on the ITCZ, Monsoon Trough, has now been designated 93 Echo. Not much has changed in the forecast with only a minimal chance of developing into anything topical.
Off in the Atlantic there are 3 tropical waves in transit with one just entering the jungles of Central America this morning.