Monday, October 3, 2016

Hurricane Watch: "Matthew Slamming Hispaniola; Southeast U.S. Landfall a Growing Threat"

From Wunderblog:
Colossal amounts of rain are soaking Haiti and the Dominican Republic as Category 4 Hurricane Matthew heads for an encounter with the western end of Hispaniola. As of the National Hurricane Center’s update at 8:00 pm EDT Monday, Matthew was located about 200 miles south of Port-au-Prince, Haiti, moving just east of due north at 8 mph. Matthew’s top sustained winds were holding at 140 mph, solidly in the Category 4 range. Just before 8 PM EDT, a Hurricane Hunter flight found a minimum surface pressure of 934 millibars, down from the 940 mb reported in the 8 PM EDT advisory. However, surface winds measured by the SFMR instrument had not yet increased. Matthew may be completing an eyewall replacement cycle, with the original small eye decaying and a larger outer band taking over. Hurricane Hunters described the new eye as ragged, elliptical and kidney-shaped, about 17 by 30 miles across. Depending on how soon this cycle is completed, it’s possible that Matthew's winds could either increase or decrease by 5 - 10 mph prior to the storm making landfall in southwest Haiti around 8 am EDT Tuesday.

As of late Monday, Hurricane Warnings were in effect for Haiti, Cuba’s eastern provinces, and the southeastern and central Bahamas. Matthew’s center is likely to pass over or very near the western tip of Haiti. This will likely spare Jamaica from widespread winds above hurricane force, although very heavy rains can still be expected (see video embedded at bottom of this post). On the other hand, Matthew’s track is close to a worst-case scenario for the beleagured nation of Haiti, as it will bring the hurricane’s more dangerous right-hand side across Hispaniola. Far southwest Haiti may experience Matthew’s small core of intense hurricane-force winds, and a much larger area of powerful south winds slamming against tall mountainsides will lead to phenomenal rains over Haiti as well as much of the Dominican Republic (DR). The rains will likely be enhanced by moisture associated with a persistent band of showers and thunderstorms that has flanked Matthew’s east side for days (see this discussion of the mysterious “blob” from Marshall Shepherd). This feature’s rapid movement toward Hispaniola has actually led to heavier rains thus far in the Dominican Republic than in Haiti. A personal weather station in Cabo Rojo, on the southern coast of the Dominican Republic near the border with Haiti, recorded 22.91” of rain in thirteen hours between 3 am and 4 pm on Monday, including a remarkable 5.33" in the hour from 6 am to 7 am. While PWS data is often suspect, these are believable rainfall amounts based on the satellite presentation of Matthew. 

NHC warns that localized rainfall amounts could total 40” over southern Haiti and the southwestern DR, with widespread 15” - 25” amounts. Massive flooding and landslides are a virtual certainty, with the impacts especially severe on Haiti’s deforested landscape. As discussed in Jeff Masters’ post this morning on the hurricane history of Matthew’s targets, one of the few analogs for this northward-moving major hurricane is Hazel (1954), which killed more than 1000 people in Haiti....MUCH MORE
Hurricane Matthew