Tropical Weather Outlook: Hurricane Sandy to Impact Region, Winds Main Threat
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Oct 27, 2012, 7:33:42 PM10/27/12
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ANNOUNCEMENT
I realize the WIDEnet has been down for quite some time, and I have been hearing more than a few complaints from members lately that they are missing their weather forecasts. Truth is, my schedule has been busy with school and all, but I can do better in terms of managing my time so more WIDEnet updates go out. I can't say at this point whether I will be pushing weekly forecasts on a regular basis, but I will certainly be covering this and other extreme weather events--the purpose the WIDEnet was designed for. Without further ado:
TROPICAL WEATHER OUTLOOK
As the first clouds from Sandy's outer bands are push through from the southeast, I want to first remind everyone that while this storm is a 600 mile wide swirl of atmospheric energy, this is not going to be the next Katrina, or even Isabel, at least for us. It looks to be more like something along the lines of Irene--disruptive, surely, but not deadly, as long as people observe proper precautions and remain inside a sturdy building during the storm. In evaluating its potential impacts, I will attempt to quantify them as much as possible by comparing them with Irene or other known quantities, to provide perspective on the real scope of the threat.
Advisories: The National Hurricane Center will not be issuing tropical watches/warnings north of Cape Hatteras, but the Potomac and the Chesapeake are under Gale- and Storm Warnings respectively, which are essentially the equivalent products to Tropical Storm Warnings (winds over 40 mph likely will occur). We currently under a Flood Watch, which means that heavy rains may cause significant flooding of rivers and low-lying areas. We are also under a Coastal Flood Watch, which means that high water may cause minor to moderate flooding along the Potomac river, and a High Wind Watch, for the winds greater than 40 mph which may occur during the storm. For more information about these hazards, please see below.
Timing: (+/- 6-12 hours)
Now (Saturday Afternoon/Evening): Clouds from Sandy continue to roll in, but we won't see any rain outside of perhaps a light sprinkle or two off the the far west/southeast of DC.
Tonight: Areas especially south and east of DC could see some showers, but the main bands of Hurricane Sandy should remain off to the southeast during the night. Winds still light
Sunday Morning/Afternoon: Showers push into the area early from SE to NW Sunday AM through Sunday afternoon, with much of the area waking up to light-moderate rain. We will begin to feel the first few light gusts from the storm during the AM hours, and sustained winds will slowly pick up into the high teens by late afternoon, but not pose any real threat. By afternoon, some eastern areas could see some heavier rain.
Sunday Evening/Overnight: Heavier rain moves in from the SE, with more intense precipitation to the east and less to the west of DC. Winds continue to pick up, but should not reach significant levels until the morning hours.
Monday Morning/Afternoon: The heaviest rain is expected to fall during this time, and winds will continue to increase past 30mph, near the level where trees begin to fall.
Monday Evening/Overnight: The worst of the storm's winds look to occur during this time, with sustained winds near 40mph and gusts potentially as high as 60. The rain should begin to slowly decrease, but looks to remain steady and relatively heavy.
Tuesday Morning/Afternoon: Strong winds should continue to occur, although peak winds will lessen by the afternoon. Rain continues to decrease, although light to moderate showers will likely continue.
Tuesday Evening/Overnight: Winds will diminish from south to north, although caution when driving is still advised. Rain should taper off to light showers as the storm pulls out.
Wednesday Morning: The threat will finally be over as the wind and rain pulls out, although winds will likely remain breezy and skies cloudy for at least some time during the day.
Hazard Analysis: (In order of threat)
Wind Threat: I expect at 50/50 chance of tropical storm force (40+ mph) sustained winds, but no matter whether the anemometer passes that mark, the wind danger will likely be the most significant hazard Sandy has in store--likely worse than during Irene, although not as bad as Isabel. I expect winds in the 35-45 mph range with gusts up to 55-60 mph to overspread the area by Monday morning, and hang around until later on Tuesday. This could cause significant damage to tree limbs and branches, and take down older or vulnerable trees, causing scattered to widespread utility, communications, and possibly transportation outages. Secure all outdoor objects, prune trees, and remain indoors and as low as possible during this period of high winds.
River/Flash Flooding (Heavy Rain) Threat: We have the potential to receive anywhere from three to eight inches of rain with this system, but at the moment, I'd say 5-6 inches is most likely. Due to the soil being significantly dryer than usual, at least 2-3 inches of rain within a six hour period is needed for the urban/suburban areas in the vicinity of Washington DC to flood, so we will likely see some low-lying or vulnerable areas flooding but not a major or widespread event. For the further-out suburbs, the main threat would be creeks and streams cresting their banks, as much more rain would be needed for areal flooding then we will likely get. In all, the heavy rain threat should be somewhat less than Irene but still present, and greatest on Monday. Depending on the track of the storm, we could also get river flooding further on in the week, so interests along waterways will need to pay close attention to that.
Coastal Flooding (Storm Surge) Threat: Although a Coastal Flood Watch is out for areas along the bay and the Potomac up to DC, I doubt we'll see water levels more than a foot or so above normal high tide levels. This could produce some minor flooding right along the river but is not the cause for much concern at this time--less so than Irene.
Tornadoes/Severe Weather: The chance for thunderstorms with Sandy is virtually nil, and the tornado threat effectively nonexistent, so no worries here.
The bottom line? Stay indoors (Monday and maybe Tuesday), and you'll be fine. And of course, a very happy hurricane to you all--just don't get spooked out about it!
UPDATE...Tomorrow morning or early tomorrow afternoon, and a brief update perhaps later tomorrow evening. See you all then...on the WIDEnet.
C. A. M. Gerlach
I realize the WIDEnet has been down for quite some time, and I have been hearing more than a few complaints from members lately that they are missing their weather forecasts. Truth is, my schedule has been busy with school and all, but I can do better in terms of managing my time so more WIDEnet updates go out. I can't say at this point whether I will be pushing weekly forecasts on a regular basis, but I will certainly be covering this and other extreme weather events--the purpose the WIDEnet was designed for. Without further ado:
TROPICAL WEATHER OUTLOOK
As the first clouds from Sandy's outer bands are push through from the southeast, I want to first remind everyone that while this storm is a 600 mile wide swirl of atmospheric energy, this is not going to be the next Katrina, or even Isabel, at least for us. It looks to be more like something along the lines of Irene--disruptive, surely, but not deadly, as long as people observe proper precautions and remain inside a sturdy building during the storm. In evaluating its potential impacts, I will attempt to quantify them as much as possible by comparing them with Irene or other known quantities, to provide perspective on the real scope of the threat.
Advisories: The National Hurricane Center will not be issuing tropical watches/warnings north of Cape Hatteras, but the Potomac and the Chesapeake are under Gale- and Storm Warnings respectively, which are essentially the equivalent products to Tropical Storm Warnings (winds over 40 mph likely will occur). We currently under a Flood Watch, which means that heavy rains may cause significant flooding of rivers and low-lying areas. We are also under a Coastal Flood Watch, which means that high water may cause minor to moderate flooding along the Potomac river, and a High Wind Watch, for the winds greater than 40 mph which may occur during the storm. For more information about these hazards, please see below.
Timing: (+/- 6-12 hours)
Now (Saturday Afternoon/Evening): Clouds from Sandy continue to roll in, but we won't see any rain outside of perhaps a light sprinkle or two off the the far west/southeast of DC.
Tonight: Areas especially south and east of DC could see some showers, but the main bands of Hurricane Sandy should remain off to the southeast during the night. Winds still light
Sunday Morning/Afternoon: Showers push into the area early from SE to NW Sunday AM through Sunday afternoon, with much of the area waking up to light-moderate rain. We will begin to feel the first few light gusts from the storm during the AM hours, and sustained winds will slowly pick up into the high teens by late afternoon, but not pose any real threat. By afternoon, some eastern areas could see some heavier rain.
Sunday Evening/Overnight: Heavier rain moves in from the SE, with more intense precipitation to the east and less to the west of DC. Winds continue to pick up, but should not reach significant levels until the morning hours.
Monday Morning/Afternoon: The heaviest rain is expected to fall during this time, and winds will continue to increase past 30mph, near the level where trees begin to fall.
Monday Evening/Overnight: The worst of the storm's winds look to occur during this time, with sustained winds near 40mph and gusts potentially as high as 60. The rain should begin to slowly decrease, but looks to remain steady and relatively heavy.
Tuesday Morning/Afternoon: Strong winds should continue to occur, although peak winds will lessen by the afternoon. Rain continues to decrease, although light to moderate showers will likely continue.
Tuesday Evening/Overnight: Winds will diminish from south to north, although caution when driving is still advised. Rain should taper off to light showers as the storm pulls out.
Wednesday Morning: The threat will finally be over as the wind and rain pulls out, although winds will likely remain breezy and skies cloudy for at least some time during the day.
Hazard Analysis: (In order of threat)
Wind Threat: I expect at 50/50 chance of tropical storm force (40+ mph) sustained winds, but no matter whether the anemometer passes that mark, the wind danger will likely be the most significant hazard Sandy has in store--likely worse than during Irene, although not as bad as Isabel. I expect winds in the 35-45 mph range with gusts up to 55-60 mph to overspread the area by Monday morning, and hang around until later on Tuesday. This could cause significant damage to tree limbs and branches, and take down older or vulnerable trees, causing scattered to widespread utility, communications, and possibly transportation outages. Secure all outdoor objects, prune trees, and remain indoors and as low as possible during this period of high winds.
River/Flash Flooding (Heavy Rain) Threat: We have the potential to receive anywhere from three to eight inches of rain with this system, but at the moment, I'd say 5-6 inches is most likely. Due to the soil being significantly dryer than usual, at least 2-3 inches of rain within a six hour period is needed for the urban/suburban areas in the vicinity of Washington DC to flood, so we will likely see some low-lying or vulnerable areas flooding but not a major or widespread event. For the further-out suburbs, the main threat would be creeks and streams cresting their banks, as much more rain would be needed for areal flooding then we will likely get. In all, the heavy rain threat should be somewhat less than Irene but still present, and greatest on Monday. Depending on the track of the storm, we could also get river flooding further on in the week, so interests along waterways will need to pay close attention to that.
Coastal Flooding (Storm Surge) Threat: Although a Coastal Flood Watch is out for areas along the bay and the Potomac up to DC, I doubt we'll see water levels more than a foot or so above normal high tide levels. This could produce some minor flooding right along the river but is not the cause for much concern at this time--less so than Irene.
Tornadoes/Severe Weather: The chance for thunderstorms with Sandy is virtually nil, and the tornado threat effectively nonexistent, so no worries here.
The bottom line? Stay indoors (Monday and maybe Tuesday), and you'll be fine. And of course, a very happy hurricane to you all--just don't get spooked out about it!
UPDATE...Tomorrow morning or early tomorrow afternoon, and a brief update perhaps later tomorrow evening. See you all then...on the WIDEnet.
C. A. M. Gerlach
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