Tropical Weather Update-2: Sandy Slower But More Intense, Projected Impacts Grow
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Oct 29, 2012, 3:50:09 PM10/29/12
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TROPICAL WEATHER OUTLOOK
Attention: This is your forecaster speaking. Hurricane Sandy is on final approach, and we will be seeing the worst of the impacts within 10 hours. Please batten down the hatches, secure any loose objects, and remain in your residences until the storm has safely passed, which should be within 24-30 hours. Thank you, and we hope you enjoy your trip through a hurricane, brought you you by...the WIDEnet Forcast System
Advisories: * High Wind Warning in effect NOW-8PM Tue * Flood Warning in effect NOW-Until 9PM EDT, extension likely * Coastal Flood Warning in effect 12AM Tue-8PM Wend * Flood Watch in effect NOW-Until 8PM Tuesday * Coastal Flood Advisory in effect NOW-12AM Tue. For more comprehensive information regarding these threats, please see the impact section below
Nowcast: More than two inches of rain have already fallen around Washington DC, with more to the east and less to the west. Winds have already gusted past 40 mph around the area, and average sustained winds are ticking past 25-30 mph. On radar, the heaviest band of rain from the storm is already well to the west of DC, but additional moderate showers are continuing to stream in from the east, and significant additional rainfall is expected. Until tomorrow morning, its all downhill from here...or at least weather conditions will be headed in that direction.
Timing: (+/- 6 hours)
Monday Afternoon: Moderate rain will continue, and will be heavy at times in some areas, especially to the north of DC. Winds will continue to steadily increase, with gusts around 45 mph by 4PM, causing some smaller branches to fall and perhaps some power flickers and isolated outages (Just as I typed this, the lights obligingly flickered once). Not a good time to be outside or driving, but get it done by 4PM if you have to.
Monday Evening: Winds continue to pick up, with gusts nearing 60 mph and sustained winds around 40 mph by this time, causing scattered power outages and felling limbs and potentially even entire trees, as well as knocking out power to considerable swaths of the region. Please stay indoors, away from windows, and on the lowest floor of your residence. Rain will continue steadily.
Monday Overnight: The strongest winds will occur, with gusts potentially past 70 mph--hurricane force--and sustained winds potentially near 60 mph. Many trees could come down, especially older or weaker specimens, so try to sleep on the lowest level of your home or in a location furthest from tall trees. Power is very likely to go out at this time, and light to moderate rain will continue.
Tuesday Morning: Strong winds with gusts potentially past 55-60 mph will likely continue to occur through noon, causing additional tree, power, and communication damage and making transportation very hazardous, even without the accumulated damage from the previous night. Rain will begin to taper off, but we could continue to see moderate showers, especially in the morning hours.
Tuesday Afternoon/Evening: Peak winds should lessen by the afternoon, but gusts will likely stay above 45 mph until around nightfall and getting around will still be difficult. Rain tapes off with a few light to moderate showers sticking around. If power has not yet gone out, it should likely stay on, although I expect that to be a moot point for the great majority of area residents.
Tuesday Overnight: Rain ends and winds continue to diminish, although it will still be blustery, with gusts in the 30s.
Wednesday: Clearing will be evident throughout the day, although we could see a few last gasps from Sandy as the day remains breezy. It will be relatively cool as well, a trend that should continue for most of the rest of the week.
Hazard Analysis: (In order of significance)
Wind Threat: My forecast of a high probability for 40 mph winds appears to be verifying, as tropical storm force winds (over 40 mph sustained) are a virtual certainty for anyone near DC. What is worse, sustained winds will probably top 55-60 mph, which imply gusts of 70-75 mph or perhaps even greater. Winds this strong would be almost as bad as Isabel, and take down numerous trees, block roads, knock out power and communications for days, and damage unsecured outdoor objects. The active threat will be largely over by noon tomorrow, but by then the accrued damage will be much more of a concern than present conditions. For a timeline on the threat, please see above.
Areal Flooding (Heavy Rain) Threat: Projected rain amount continue to increase, and I now project the DC area will receive an additional 4-5 or so inches of rain on top of the 2.5 in we have already received, brining our total to 6-7 inches around the metro area, with more to the north and east, and less to the south and west. While this will cause substantial pooling of water on roadways and low-lying areas making travel hazardous, the biggest threat will be with streams, creeks, and smaller rivers, as they will quickly rise out of their banks today and into tomorrow. Anyone living near a water feature should remain alert for rising water and be prepared to secure themselves and their property from flooding, and driving about the area today and tomorrow should be avoided, as even the smallest waterways can flood a road in these conditions.
Coastal/River Flooding (Storm Surge) Threat: We shouldn't see any more than minor tidal flooding today, but tomorrow could bring potentially moderate to significant flooding along the Alexandria waterfront and nearby localities as waters rise over two feet above normal during high tide Tuesday morning and evening. Residences and businesses within a block of the river should remain alert and take steps to protect their property in the event of rising waters. Perhaps an even greater threat comes later in the week in the Wednesday-Friday period, as the Potomac rises due to floodwaters and tides are still high due to the full moon. If this does pose a serious threat, I will send out a short statement later in the week, but impacts are more likely to occur on the upstream side of Alexandria and DC.
Tornadoes/Severe Weather: None.
UPDATE...At 6-7PM tonight if the situation changes and we still posses power. Due to likely power and comms being down for both affected members and the WIDEnet Operations Center, this will likely be the last update excepting extraordinary circumstances, as although we do have limited backup power, our backup internet link (128 kbps) is far too slow to reliably downlink the required products to make a forecast. Stay safe everyone, and should I fail to transmit a 7PM final update, see you all after the storm.
C. A. M. Gerlach
Attention: This is your forecaster speaking. Hurricane Sandy is on final approach, and we will be seeing the worst of the impacts within 10 hours. Please batten down the hatches, secure any loose objects, and remain in your residences until the storm has safely passed, which should be within 24-30 hours. Thank you, and we hope you enjoy your trip through a hurricane, brought you you by...the WIDEnet Forcast System
Advisories: * High Wind Warning in effect NOW-8PM Tue * Flood Warning in effect NOW-Until 9PM EDT, extension likely * Coastal Flood Warning in effect 12AM Tue-8PM Wend * Flood Watch in effect NOW-Until 8PM Tuesday * Coastal Flood Advisory in effect NOW-12AM Tue. For more comprehensive information regarding these threats, please see the impact section below
Nowcast: More than two inches of rain have already fallen around Washington DC, with more to the east and less to the west. Winds have already gusted past 40 mph around the area, and average sustained winds are ticking past 25-30 mph. On radar, the heaviest band of rain from the storm is already well to the west of DC, but additional moderate showers are continuing to stream in from the east, and significant additional rainfall is expected. Until tomorrow morning, its all downhill from here...or at least weather conditions will be headed in that direction.
Timing: (+/- 6 hours)
Monday Afternoon: Moderate rain will continue, and will be heavy at times in some areas, especially to the north of DC. Winds will continue to steadily increase, with gusts around 45 mph by 4PM, causing some smaller branches to fall and perhaps some power flickers and isolated outages (Just as I typed this, the lights obligingly flickered once). Not a good time to be outside or driving, but get it done by 4PM if you have to.
Monday Evening: Winds continue to pick up, with gusts nearing 60 mph and sustained winds around 40 mph by this time, causing scattered power outages and felling limbs and potentially even entire trees, as well as knocking out power to considerable swaths of the region. Please stay indoors, away from windows, and on the lowest floor of your residence. Rain will continue steadily.
Monday Overnight: The strongest winds will occur, with gusts potentially past 70 mph--hurricane force--and sustained winds potentially near 60 mph. Many trees could come down, especially older or weaker specimens, so try to sleep on the lowest level of your home or in a location furthest from tall trees. Power is very likely to go out at this time, and light to moderate rain will continue.
Tuesday Morning: Strong winds with gusts potentially past 55-60 mph will likely continue to occur through noon, causing additional tree, power, and communication damage and making transportation very hazardous, even without the accumulated damage from the previous night. Rain will begin to taper off, but we could continue to see moderate showers, especially in the morning hours.
Tuesday Afternoon/Evening: Peak winds should lessen by the afternoon, but gusts will likely stay above 45 mph until around nightfall and getting around will still be difficult. Rain tapes off with a few light to moderate showers sticking around. If power has not yet gone out, it should likely stay on, although I expect that to be a moot point for the great majority of area residents.
Tuesday Overnight: Rain ends and winds continue to diminish, although it will still be blustery, with gusts in the 30s.
Wednesday: Clearing will be evident throughout the day, although we could see a few last gasps from Sandy as the day remains breezy. It will be relatively cool as well, a trend that should continue for most of the rest of the week.
Hazard Analysis: (In order of significance)
Wind Threat: My forecast of a high probability for 40 mph winds appears to be verifying, as tropical storm force winds (over 40 mph sustained) are a virtual certainty for anyone near DC. What is worse, sustained winds will probably top 55-60 mph, which imply gusts of 70-75 mph or perhaps even greater. Winds this strong would be almost as bad as Isabel, and take down numerous trees, block roads, knock out power and communications for days, and damage unsecured outdoor objects. The active threat will be largely over by noon tomorrow, but by then the accrued damage will be much more of a concern than present conditions. For a timeline on the threat, please see above.
Areal Flooding (Heavy Rain) Threat: Projected rain amount continue to increase, and I now project the DC area will receive an additional 4-5 or so inches of rain on top of the 2.5 in we have already received, brining our total to 6-7 inches around the metro area, with more to the north and east, and less to the south and west. While this will cause substantial pooling of water on roadways and low-lying areas making travel hazardous, the biggest threat will be with streams, creeks, and smaller rivers, as they will quickly rise out of their banks today and into tomorrow. Anyone living near a water feature should remain alert for rising water and be prepared to secure themselves and their property from flooding, and driving about the area today and tomorrow should be avoided, as even the smallest waterways can flood a road in these conditions.
Coastal/River Flooding (Storm Surge) Threat: We shouldn't see any more than minor tidal flooding today, but tomorrow could bring potentially moderate to significant flooding along the Alexandria waterfront and nearby localities as waters rise over two feet above normal during high tide Tuesday morning and evening. Residences and businesses within a block of the river should remain alert and take steps to protect their property in the event of rising waters. Perhaps an even greater threat comes later in the week in the Wednesday-Friday period, as the Potomac rises due to floodwaters and tides are still high due to the full moon. If this does pose a serious threat, I will send out a short statement later in the week, but impacts are more likely to occur on the upstream side of Alexandria and DC.
Tornadoes/Severe Weather: None.
UPDATE...At 6-7PM tonight if the situation changes and we still posses power. Due to likely power and comms being down for both affected members and the WIDEnet Operations Center, this will likely be the last update excepting extraordinary circumstances, as although we do have limited backup power, our backup internet link (128 kbps) is far too slow to reliably downlink the required products to make a forecast. Stay safe everyone, and should I fail to transmit a 7PM final update, see you all after the storm.
C. A. M. Gerlach
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