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A weakened Tomas still a grave danger to Haiti

By: Dr. Jeff Masters, 1:38 PM GMT on November 03, 2010

As this record-breaking third busiest Atlantic hurricane season in history unfolded, I marveled that earthquake-ravaged Haiti managed to dodge significant rain-making tropical storms throughout the peak months of August, September, and October. Cruel fate will not allow Haiti to escape the entire season unscathed, though, as a late-season November storm already proven to be a killer--Tomas--takes aim at Haiti. Tomas has struggled mightily over the past few days, and is now a tropical depression. However, even if it does not reach hurricane strength, Tomas is still likely to bring heavy rains capable of causing disastrous flooding in defenseless Haiti. It doesn't take much rain to cause a flooding disaster in Haiti--ordinary seasonal heavy rains have killed 23 people in southern Haiti over the past month, including twelve people in Port-au-Prince this past weekend. According to the Associated Press, most of last weekend's deaths occurred when surging rivers burst through houses built in ravines. With the soils already saturated from last weekend's rains, the stage is set in Haiti for a significant flooding disaster capable of causing heavy loss of life. I believe it is 30% likely that Tomas will stay far enough west of the Haiti earthquake zone so that rains will be limited to 1 - 4 inches to the region, causing only modest flooding problems and little or no loss of life. More likely (40% chance) is the possibility of major flooding due to 4 - 8 inches of rains. Finally, I expect a 30% chance that heavier rains of 5 - 20 inches over Haiti will cause catastrophic flooding like experienced in 2008's four hurricanes. Potential flooding disasters are not possible just in the earthquake zone, but also in northern Haiti and the southwestern peninsula of Haiti. So, keep praying for the people of Haiti, they need all the help they can get.

Figure 1. Morning satellite image of Tomas.

Tomas struggling
Satellite loops of Tomas show a very disorganized tropical depression, with clumps of heavy thunderstorms scattered about the center in a vaguely cyclonic fashion. However, the thunderstorms are increasing in intensity and areal coverage this morning, and upper-level outflow is now well-established to the north. Given the highly favorable environment for intensification Tomas is in, the current satellite presentation suggests that Tomas is at the beginning of a period of steady intensification that will take it back to tropical storm strength by tonight, and to Category 1 hurricane strength by Friday. A hurricane hunter aircraft will have a better estimate of Tomas' strength by early this afternoon.

Track forecast for Tomas
The ridge of high pressure pushing Tomas to the west has weakened, allowing Tomas to slow down to a forward speed of 4 mph this morning. A trough of low pressure approaching the eastern U.S. has now begun to pull Tomas more to the west-northwest, and a sharper northward turn will develop today, and become a north-northeast motion by Friday. This motion should take Tomas just east of Jamaica and over western Haiti on Friday. NHC is giving Port-au-Prince, Haiti, a 46% chance of receiving tropical storm force winds, and a 5% chance of hurricane force winds. These odds are 45% and 4%, respectively for Kingston, Jamaica, and 19% and 2% for Santo Domingo in the Dominican Republic. Heavy rains from Tomas will begin affecting Jamaica and southwestern Haiti beginning on Thursday afternoon, and will spread to eastern Cuba, the Dominican Republic, and the rest of Haiti by Friday morning. Tomas will probably not be as bad for Jamaica as Tropical Storm Nicole in September, which killed 14 and did $245 million in damage. Nicole's rains lasted three days in Jamaica, and Tomas' rains should last at most 1 1/2 days on the island.

While all of the computer models agree on the motion of Tomas through Friday, there continue to be major differences in forecasts for what happens beginning on Saturday. The trough of low pressure pulling Tomas to the north is expected to lift out, leaving Tomas behind in an area of weak steering currents. The official NHC forecast follows the GFS and ECMWF models, which have been very consistent and reliable predicting the track of Tomas. These models forecast that Tomas will stall several hundred miles north of Haiti, then move slowly eastward. However, the GFDL model stalls Tomas just west of Port-au-Prince Haiti, predicting a days-long period of heavy rains for Haiti. The UKMET and NOGAPS model solutions are also unpleasant for Haiti; these models predict that Tomas will stall over the Turks and Caicos Islands, then drift south over eastern Cuba and western Haiti. The farther north Tomas gets, the higher wind shear will be, and the weaker the storm will get. However, if Tomas stays near the latitude of Hispaniola, wind shear will be low to moderate, and the storm will be able to maintain its strength if the center stays over water. Given recent model trends, I believe a multi-day period of heavy rains that could total twenty inches for eastern Cuba, Haiti, and the western Dominican Republic is at least 30% likely.

Intensity forecast for Tomas
Tomas' struggles to intensify over the past day are difficult to explain scientifically, as all the data we have suggests the storm should have strengthened. Our ability to forecast intensification is limited by the poor availability of data over the oceans, though, and there must be a layer of wind shear or dry air our sensors cannot pick out that is interfering with development. In the absence of any concrete evidence on what is causing Tomas' current troubles, I must continue to forecast intensification over the coming two days. Wind shear as diagnosed by the SHIPS model has dropped to the low range, 5 - 10, and is predicted to stay in the low range for the next three days. The atmosphere is very moist in the Caribbean, as seen on water vapor satellite imagery, and the models predict a very moist atmosphere will surround Tomas for the remainder of the week. With SSTs at a record warm 29.5°C and a very high ocean heat content, there is a substantial danger that Tomas will undergo a period of rapid intensification if has time to build an eyewall. Crucially, the storm has waited too long to begin this process, and it now appears unlikely that Tomas will have time to grow beyond Category 1 hurricane strength before landfall in Haiti on Friday. NHC is giving Tomas a 5% chance of reaching Category 3+ strength, which is a reasonable forecast. With the atmosphere expected to be very moist, it is likely that Tomas will dump very heavy rains of 4 - 8 inches over much of Haiti, even if Tomas strikes as a tropical storm. Rains of this magnitude are capable of causing heavy loss of life due to extreme floods running down Haiti's deforested mountain slopes. Portlight.org is preparing to send their mobile kitchen with enough food to feed 500 people per day, if the threat from Tomas materializes as forecast.

Haiti's hurricane history
In many ways, the hurricane season of 2008 was the cruelest ever experienced in Haiti. Four storms--Fay, Gustav, Hanna, and Ike--dumped heavy rains on the impoverished nation. The rugged hillsides, stripped bare of 98% of their forest cover thanks to deforestation, let flood waters rampage into large areas of the country. Particularly hard-hit was Gonaives, the fourth largest city. According to reliefweb.org, Haiti suffered 793 killed, with 310 missing and another 593 injured. The hurricanes destroyed 22,702 homes and damaged another 84,625. About 800,000 people were affected--8% of Haiti's total population. The flood wiped out 70% of Haiti's crops, resulting in dozens of deaths of children due to malnutrition in the months following the storms. Damage was estimated at over $1 billion, the costliest natural disaster in Haitian history, prior to the 2010 earthquake. The damage amounted to over 5% of the country's $17 billion GDP, a staggering blow for a nation so poor.

Figure 2. The flooded city of Gonaives after Hurricane Hanna, September 3, 2008. Image credit: Lambi Fund of Haiti.

Two thousand and eight was only one of many years hurricane have brought untold misery to Haiti. Hurricane Jeanne of 2004 passed just north of the country as a tropical storm, dumping 13 inches of rains on the nation's northern mountains. The resulting floods killed over 3000 people, mostly in the town of Gonaives. Jeanne ranks as the 12th deadliest hurricane of all time on the list of the 30 most deadly Atlantic hurricanes . Unfortunately for Haiti, its name appears several times on this list. Hurricane Flora killed over 8000 people in 1963, making it the 6th most deadly hurricane ever. An unnamed 1935 storm killed over 2000, and Hurricane Hazel killed over 1000 in 1954. More recently, Hurricane Gordon killed over 1000 Haitians in 1994, and in 1998, Hurricane Georges killed over 400 while destroying 80% of all the crops in the country.

Surprisingly, only six major Category 3 and stronger hurricanes have struck Haiti since 1851. The strongest hurricane to hit Haiti was Hurricane Cleo of 1964, which struck the southwestern peninsula as a Category 4 storm with 150 mph winds, killing 192 people. Haiti's only other Category 4 storm was Hurricane Flora of 1963, which had 145 mph winds when it struck the southwestern peninsula, killing 8000. No Category 5 hurricanes have hit Haiti since 1851. The most recent Category 3 hurricane to hit Haiti was Hurricane David of 1979, which crossed northern Haiti as a Category 3 hurricane with 115 mph winds after hitting the Dominican Republic as a Category 5 hurricane with 170 mph winds. David weakened quickly to a tropical storm after crossing into Haiti, as caused no deaths in the country. The other major hurricanes to strike Haiti were Hurricane Inez of 1966, which hit southern Haiti as a Category 3 hurricane with 115 mph winds, killing 480 people; Hurricane Katie of 1955, which hit near the Haiti/Dominican Republic border with 115 mph winds, killing 7; and Hurricane Five of 1873, which hit the southwestern peninsula with 115 mph winds.

Figure 3.Two of 2008's four tropical cyclones that ravaged Haiti: Tropical Storm Hanna (right) and Hurricane Gustav (left). Image taken at 10:40 am EDT September 1, 2008. Image credit: NASA/GSFC.

Why does Haiti suffer a seemingly disproportionate number of flooding disasters? The answer in that in large part, these are not natural disasters--they are human-caused disasters. Haiti is the poorest nation in the Western Hemisphere. With oil too expensive for the impoverished nation, charcoal from burnt trees has provided 85% or more of the energy in Haiti for decades. As a result, Haiti's 8 million poor have relentlessly hunted and chopped down huge amounts of forest, leaving denuded mountain slopes that rainwater washes down unimpeded. Back in 1980, Haiti still had 25% of its forests, allowing the nation to withstand heavy rain events like 1979's Category 3 Hurricane David without loss of life. But as of 2004, only 1.4% of Haiti's forests remained. Jeanne and Gordon were not even hurricanes--merely strong tropical storms--when they stuck Haiti, but the almost total lack of tree cover contributed to the devastating floods that killed thousands. And it doesn't even take a tropical storm to devastate Haiti--in May of 2004, three days of heavy rains from a tropical disturbance dumped more than 18 inches of rain in the mountains, triggering floods that killed over 2600 people.

What can be done to reduce these human-worsened natural disasters? Education and poverty eradication are critical to improving things. In addition, reforestation efforts and promotion of alternative fuels are needed.

In the past two decades, the U.S. Agency for International Development has planted some 60 million trees, while an estimated 10 to 20 million of these are cut down each year, according to the USAID director in Haiti, David Adams. If you're looking for a promising way to make a charitable donation to help Haitian flood victims, considering supporting the Lambi Fund of Haiti, which is very active in promoting reforestation efforts, use of alternative fuels, and infrastructure improvements at a grass-roots level to help avert future flood disasters.

Organizations Active in Haitian Relief Efforts:
Portlight disaster relief
Lambi Fund of Haiti
Haiti Hope Fund
Catholic Relief Services of Haiti

Next update
I'll have an update later today if there is a significant change with Tomas to report. Otherwise, expect the next update Thursday morning.

Note that the section on Haiti's hurricane history is now a permanent link in the "Articles of interest" section on our Tropical & Hurricane web page.

Jeff Masters


The views of the author are his/her own and do not necessarily represent the position of The Weather Company or its parent, IBM.