As the Earth’s axis tilts while orbiting the Sun, we are approaching the date when the Sun will be directly above the equator and one of two times during the year when day and night will have equal duration. This time, which will take place this coming Wednesday, September 23, 2010 at 11:09 EST, marks the autumnal equinox and the start of the fall season of 2010.
So, we are seeing the last days of summer 2010 and as we take a look at Earth’s oceans and atmosphere we see plenty of actual and potential tropical cyclone activity worldwide. Most of the activity is in the larger Atlantic basin where we have hurricane IGOR and tropical storm JULIA moving toward the southeast over open ocean waters, and a large tropical wave just west of the Cape Verde Islands that appears on the verge of becoming a tropical cyclone, plus several other waves in the Caribbean, near the windward Islands and the eastern Atlantic. There is also a typhoon and a tropical depression in the western Pacific and another tropical wave in the eastern Pacific. Additionally there are several tropical waves and cells of stormy weather over equatorial Africa and the Indian Ocean all moving westward toward the still quite warm waters of the Atlantic.
2010 is shaping-up to be somewhat different than your typical year with respect to tropical cyclone activity. The eastern Pacific basin, which usually averages 50% – 60% more tropical cyclones than the greater Atlantic basin has been somewhat quiet so far, with only five named storms versus eleven already in the Atlantic. The central Pacific region has also been extremely quiet with no named storms so far in 2010. However the southern Pacific and Indian oceans have see plenty of activity so far. It is clear that several factors including the La Nina event now under way off the Pacific coast of Peru, the position of the Bermuda high and water temperatures over the Atlantic, the direction of the Julian-Madden oscillation and the water content in the atmosphere are all contributing to shaping up the 2010 worldwide hurricane season.
On a worldwide basis we continue to see high levels of moisture in the atmosphere particularly near the equator. In fact satellite observations today show large quantities of precipitable water in the atmosphere, which in some regions is up to 70-80 mm/hr. This high moisture content in the atmosphere creates an environment conducive to wet hurricanes, meaning storms that generate large amounts of rain regardless of the intensity of the cyclone itself. Recent reports from the passage of Hurricane Karl through the Yucatan peninsula as a category 1 hurricane refer to large amounts of intense rain, as the most damaging component of the storm. Other recent storms have also generated vast quantities of rain causing flash flooding and mudslides in affected communities.
Over in the Atlantic conditions appear favorable for continued tropical cyclone activity as the number of tropical waves riding along ‘Hurricane alley” and the ‘assembly line’ over equatorial Africa appears to have no end in sight at least for the next 2 – 3 weeks. Only time will show if all these waves are able to generate tropical cyclones, but for the time being all interests around the greater Atlantic basin, including island nations and countries bordering on the Caribbean and Gulf and USA Atlantic coastal regions must closely monitor all of this activity. We must all pay attention! Be prepared!! And above all always practice MITIGATION!!!
Three tropical cyclones are active in the Atlantic and Caribbean basins: IGOR, JULIA and KARL. Julia became the 11th named storm of the 2010 Atlantic hurricane season as it entered the period that historically has been the peak of the annual season, so there is more to come.
We have known this trio of storms for quite some time as they were mere tropical waves or areas of disturbed weather, emerging from equatorial Africa over the warm waters of the Atlantic to ride on Hurricane Alley as Igor and Julia have done or crossing into the Caribbean as just a blob of bad weather generating plenty of rain over the Virgin Islands and Puerto Rico and Hispaniola as what is now Tropical Storm Karl did. You can actually follow this storms from genesis to current stage through earlier postings on this site. All of these storms have been part of the “belt” of tropical activity we have highlighted and illustrated on this blog.
As we look eastward toward the Cape Verde Islands, the eastern Atlantic and equatorial Africa, there are more tropical waves being generated above the hot and humid tropical forests in Africa and moving west toward the Atlantic, which continues to be quite warm. What is noticeable already is how these tropical waves are being generated farther south and closer to the equator than say six weeks ago, a sign of the approaching change in seasons; as summer winds down and fall approaches the warmest Atlantic waters and coupled atmosphere are shifting southward.