Tag Archives: Precipitable Water


Composite satellite view on 23 September 2010 at 1345 EST showing water vapor in the atmosphere. Tropical depression #15, the remnants of Tropical Storm JULIA and now Tropical Depression LISA are identified.

Three days ago in our posting “The Last Days of Summer 2010” we identified several tropical waves in the larger Atlantic basin including one approaching the Lesser Antilles, subsequently we questioned the potential for further development of the same tropical wave as it straddled the Lesser Antilles and started to penetrate the eastern Caribbean. What was significant about this tropical wave then was its enormous size; here we had a system that was more than 1,100 miles long by more than 800 miles wide, quite large indeed!

Today as if to mark the end of summer and arrival of fall this tropical wave got better organized and stronger as it became Tropical Depression #15 of the 2010 Atlantic hurricane season. As of 1400 EST the system’s “center” was located at LAT 13.9N LONG 76.2W moving toward the west with 35 mph sustained winds, placing it some 500 miles to the east/southeast of Cape “Gracias a Dios” at the border between Nicaragua and Honduras, and approximately 1,400 miles from Chetumal, capital of the state of Quintana Roo in Mexico’ Yucatan peninsula.

Visible light satellite view of Tropical Depression #15 on 23 September 2010 at 1445 EST.
Map based on satellite remote-sensing observations showing sea surface temperatures. Notice how most of the Caribbean has the warmest surface waters. The position of Tropical Depression #15 is identified by the yellow icon and name.

Tropical depression #15 continues to be quite a large  system, which is moving over the warmest waters of the Caribbean into an environment with large amounts of moisture (precipitable water) in the atmosphere over an area than encompasses the Caribbean, the Antilles, all of Central America, northern Colombia and Venezuela, the eastern Pacific off the coasts of Mexico and Central America and peripheral areas. It is clear that between the warm sea surface waters, the large amount of moisture in the atmosphere, and the numerous thunderstorms and cells of disturbed weather in its immediate environment, Tropical Depression #15 has the potential for further development in the next day or so and the capacity for affecting quite a large area around the Caribbean basin  GOES satellite view of the larger Caribbean basin on 23 September 2010 showing the large amount of water vapor and precipitable water in the atmosphere over a large region around Tropical Depression #15, which is identified by the solid yellow outline.and beyond.

With the prospect for this cyclone to be a rain-maker, interests in Central America and the Yucatan Peninsula in Mexico, which recently suffered extreme rain and flooding with the passage of Hurricane KARL, and previously tropical Storm HERMINE, may be in for a repeat in the next one to three days. This is a reminder that WIND and WATER are the main damage components of a hurricane, and even when the wind does not cause much damage, extreme rain, and storm surge may lead to flash flooding in coastal regions generating large amounts of damage.

Tropical weather outlook for the Gulf, Caribbean and Atlantic region posted by the National Hurricane center on 23 september 2010 at 1400 EST.

  Currently, on 23 September 2010 at 1700 EST, Tropical Depression #15 is tracking west at a rapid pace of 15 mph with sustained winds of 35 mph. It if continues along this track taking into account the degree of uncertainty, the margin of error in predicting the future path of the system, it is clear than Nicaragua, Honduras, Guatemala, Belize and Quintana Roo, Mexico need to consider this hazard a direct threat to its Caribbean coastal regions. However all countries surrounding the Caribbean basin should brace for the possibility of extreme rain events over the next couple of days.

Keep visiting this site for updates and additional commentary on tropical depression #15’s future development and progress.


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.

Worldwide satellite view of Earth identifying all active tropical cyclones on 20 September 2010 at 0740 EST.

 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.

Composite satellite view showing precipitable water in the atmosphere on 20 September 2010 at 0740 EST. The band of color ranging from yellows to orange and dark brown represents the highest concentrations of precipitable water in the atmosphere, with the darker browns depicting potential precipitation in the range of 70-80 mm (3.1+ inches) per hour.

 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.

Global mosaic showing a satellite view of Earth from the eastern Pacific, through the Caribbean, Atlantic and equatorial Africa to the Indian ocean on 20 September 2010. Solid yellow outlines identify hurricane IGOR and tropical storm JULIA as they move over the open waters of the Atlantic toward the northeast. Several tropical waves or cells of disturbed weather, which could potentially generate tropical cyclones, are shown within dotted yellow outlines. The tropical wave just to the west of the Cape Verde Islands appears to be getting better organized and stronger with a high probability for further development within the next few hours.

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!!!