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Question: Will Falls Lake Dam need to have water released like after Fran and Floyd, which will then prolong the flooding and misery down east in Goldsboro and especially Kinston? — Tanja
Answer: The Corps of Engineers reported that they cut releases from falls lake to minimum levels several days before Matthew's arrival, and since the storm they maintained minimum release flows from the reservoir, which resulted in holding back over 34 billion gallons of water that would otherwise have progressed down the Neuse basin. They planned, in coordination with municipalities downstream that were impacted by serious flooding in Matthew's wake, to delay any increase in releases from the reservoir until Monday October 17th and to manage release rates at lower than typical values so as not to return downstream flows and water levels to flood stage or above. The Corps has been posting updates on the situation at www.facebook.com/FallsLakeNC/.
Oct. 22, 2016 | Tags: flooding, water resources
Question: Could you please tell me how much rainfall there was in Spring Lake from the hurricane? — Diane
Answer: We couldn't find a specific gauge report from Spring Lake, but did turn up several sites nearby that showed a range of rainfall totals from the hurricane, together with the frontal boundary that brought some light rain the day before it arrived, that ranged from around 9 inches to as much as almost 15. Some examples include 8.6 inches at Pope Field, 9.8 inches at Simmons AAF, 10.7 and 14.7 inches at volunteer observer sites just southwest and just north of Fayetteville, and 14.9 inches at the Fayetteville airport. Anyone who'd like to check totals at other locations can find reports from official airport sensors through the "Almanac" page on our web site by using the "get historical data" function and then changing from the default RDU location to other sites, and you can also find numerous reports from the volunteer network called the Community Collaborative Rain, Hail and Snow network (CoCoRaHS) at www.cocorahs.org.
Oct. 21, 2016 | Tags: hurricanes, past weather, rain
Question: I placed a five gallon sheetrock bucket in the back yard in a open place Friday evening as Matthew approached and accumulated 10.25 inches of rain. Would that be an accurate measurement? — Bruce
Answer: That seems like a reasonably good measurement, assuming the bucket has a flat bottom and the sides are vertical (perpendicular to the bottom). It's also important that the bucket was sitting level and was not in an area where it would be affected by nearby trees or buildings that can affect the reading, by either blocking some of the rain, or by concentrating rain that runs off the side of a roof or some branches of a tree, etc). You did note an "open area," and your number does run pretty close to other radar and gauge estimates from nearby locations.
Oct. 20, 2016 | Tags: hurricanes, instruments, rain
Question: How many miles did Matthew travel once it formed in the Atlantic as a TS until it became sub-tropical? Is this unusually impressive? — David
Answer: We haven't seen an official wrap-up that includes a precision measurement of Matthew's path length. However, we used some path-length tools and a roughly drawn path of the storm to come up with an "order of magnitude" rough number of somewhere around 3300 miles or so. That's a long track, but not inordinately so for storms that form over the south or east Atlantic. When compared to the longest distance on record for an Atlantic tropical cyclone, it pales in comparison to Hurricane Faith from 1966, which started southwest of the Cape Verde Islands and proceeded on a 6870-mile journey as a tropical system, across the Atlantic to north of the Bahamas and well east of NC, then off to the northwest and eventually crossing the North Sea in the vicinity of the Faroe Islands before becoming extratropical. The tropical cyclone having the longest recorded path length was in the Pacific (crossing two tropical basins) in 1994, as Hurricane John (later referred to as Typhoon John when it crossed into the northwest Pacific) traveled about 7115 miles over the course of 31 days.
Oct. 19, 2016 | Tags: hurricanes, records/extremes
Question: I noticed just as Matthew arrived in the Carolinas the storm was greatly "deformed" and only precipitated on land areas while earlier it was well defined. Why is that/what interacted with it to cause such rainfall so far from the center? — Raed
Answer: When tropical cyclones are well at sea and/or rather far south in the tropics, they are often far from other significant weather systems or features and have more of a "classic" tropical organizational structure, involving a near-symmetric shape and precipitation that largely occurs along a number of curved inflow bands and within an eyewall that encloses the center of circulation. This structure often changes as the systems move north and begin to interact with continental land surfaces and other weather features associated with the more northerly positioned jet stream and polar front. In the case of Matthew, as it moved north along the GA/SC coast, it interacted with a stationary front in the lower atmosphere that had been developing for several days off the coast, eventually driving that front a couple counties or so inland, which set up a scenario in which low level air west of the front was a little cooler and had lower dew points, making it less dense than the warmer and moister tropical air east and southeast of the boundary. This created a tendency for th tropical air to glide upward sharply as it followed in over the cooler slab of air, creating strong upward motion that translated into very heavy rain over an extended area and for extended periods, while to the east of the front there was some heavy precipitation, but it remained in a more typically tropical banded orientation that made rain along the coast more off/on and kept overall totals lower there. In addition, as Matthew neared the southern coast of our state, an upper level trough to the west and a cold front also approached and interacted with the storm, helping to increase the "hybrid" structure you noticed, and eventually absorbing the system as a post-tropical, weakening circulation.
Oct. 18, 2016 | Tags: hurricanes, past weather
Question: What happened to result in Matthew not exiting to the east along the NC coast and taking the loop south that we were expecting to take place? — Neena Fortune
Answer: Matthew was subject to a pretty complex interaction of a number of mid-level features that affected the steering flow that moved it along, with a ridge of high pressure to its east that was pushing it north and northwest for a while and was, at one point, expected to break down rapidly as another pair of high pressure ridges aloft intensified, one to the south of the storm and another to its west (all that as an upper level trough also moved in from the west and brushed by north of the storm). For a couple of days mid-week prior to landfall, observed data taken with balloons, surface observations and aircraft largely led to computer projections that caused the high south of the storm and the approaching upper trough to turn it eastward somewhere around the GA/SC border area and then for the high pressure ridge to the west to sharpen, capturing the storm in a northerly flow that would push it southward. As it eventually turned out, the first ridge east of the storm was a little slower to break down than initially forecast, which kept the storm moving north and northeastward for a longer period near the coast, and the ridge to the west never extended as sharply to the north as had been projected, which allowed the storm to track eastward as it moved away from NC. While this happened, a cold front and upper trough caught up with and absorbed the storm so that it no longer remained a distinct entity, but instead pulled away northeast as a weakening non-tropical low. In some of these cases, the difference between the projected positions and intensities of surrounding features and how they eventually developed really weren't all that large, which illustrates how sensitive a tropical cyclone track can be to these kinds of influences. Of course, in terms of impacts, fairly small changes in the track and the way the storm interacts with other features in the vicinity can lead to large changes in wind speeds, rainfall amounts and storm surges for specific locations.
Oct. 17, 2016 | Tags: hurricanes, past weather
Question: Often, there is a significant delay between the intense part of a heavy storm like Matthew and the onset of the worst flooding. I believe this was true of Katrina. What accounts for the fact that flooding can be at its most severe long after the rain has stopped? — Jay Exum
Answer: Two types of flooding that can somewhat overlap but can also be rather distinct can occur with situations like we saw with Matthew's passage, and as you mentioned, in Katrina back in 2005. In that storm, a number of levees and large pumps in the New Orleans area initially held up to the heavy rains and high winds associated with the storm, but eventually failed and allowed very substantial flooding to develop rapidly on a delayed basis.
In our area with Matthew, the very heavy and sustained downpours that occurred later Friday night into Saturday evening resulted in many initial reports of flash flooding as small creeks and streams quickly filled up and overflowed, and many drainage systems in urban or semi-urban areas simply could not keep up with the rapid runoff, especially where debris from gusty winds clogged entry points. In the longer term, the water that fell onto larger watersheds gradually collects from all of those small streams to larger tributaries, some running off across the surface, some soaking into the ground but still flowing slowly toward those streams, and eventually emptying into main stem rivers like the Tar, Neuse, Cape Fear and Roanoke, along with some smaller rivers within those watershed basins. This process gradually concentrates water from a very large area into much smaller ones in a slow surge that travels down those drainage basins toward the coast, and can result in days of elevated water levels at locations successively downstream. Hence, we've seen increasing flood problems on a delay of a couple of days in places like Rocky Mount, Tarboro and Greenville along the Tar River; Smithfield, Goldsboro and Kinston along the Neuse; and Lumberton along the Lumber, among a number of other locations and waterways, some of these requiring evacuations and rescues by means of high-clearance vehicles, boats or helicopters.
Oct. 16, 2016 | Tags: flooding, rain
Question: Re-phrasing an earlier question: What's the latest date that Raleigh reached a low in the 40s? — Randy Yelverton
Question: I have heard that the last major hurricane (cat 3 or higher) to make landfall in the US was Rita in 2005. Does "make landfall" mean the actual eye comes ashore? I ask because I'm wondering if Matthew "made landfall" before dropping to a cat 1 or 2. — Anonymous
Answer: Actually, Hurricane Wilma made landfall in Florida as a category 3 storm in 2005, and was the last such storm at landfall in the U.S. - Matthew was a major hurricane for part of its history, of course, but when it technically made landfall near Mclellanville, SC, it had weakened to a Category 1 system.
Oct. 14, 2016 | Tags: hurricanes, past weather
Question: Regarding probability of precipitation, does this reflect the chance that there will be any precipitation within some time period such as an hour, or is it just that at a given point in time the probability that it will be raining? — Jack Wolf
Answer: Technically, it does include both a location and a span of time, and also a threshold amount of precipitation. For example, the most typical chance of precipitation is the probability that .01-inch of precipitation (the amount considered "measurable") will occur within a 12-hour period. One can also calculate probabilities that, for example, 1-inch of rain will occur in a 6-hour period, one-quarter inch will fall within 3-hours, measurable precipitation will fall in one hour, and so on.
Oct. 13, 2016 | Tags: general meteorology, maps & codes
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Published: 2007-10-09 14:40:00
Updated: 2014-06-24 16:06:51