National Weather ServicePhiladelphia/Mt. Holly
Weather BriefingPotential Impacts of
Hurricane Irene August 27th-August 28th, 2011
Prepared 345 PM EDT – Wednesday August 24, 2011Gary Szatkowski
NOAA’s National Weather ServicePhiladelphia/Mt. Holly NJ Forecast office
Weather.gov/phi
National Weather ServicePhiladelphia/Mt. Holly
Purpose of briefing
• Briefing #3 for event• Promote situational
awareness for emergency management community & partners
• Provide guidance for planning efforts
• Briefing applies to Mount Holly service area – shaded in green on map
National Weather ServicePhiladelphia/Mt. Holly
Changes from previous briefing
• The main time for hurricane impacts starts Saturday night, August 27th and ends during Sunday night, August 28th.
• The National Hurricane Center path forecasts have trended slightly to the right (east) compared to 24 hours ago, though there was not much change to the path forecast over the past 6 hours.
National Weather ServicePhiladelphia/Mt. Holly
Executive Summary• Hurricane Irene will likely be a threat to our forecast area later this week. • The most likely time to feel its effects are Saturday night August 27th into Sunday night, August 28th
• Given how much recent rainfall we have experienced, additional significant rainfall carries a very high risk of major flooding• The threat from winds and coastal flooding depends on the final track of the storm• Remember, at this time range, average errors for storm location are roughly 200 miles. Use this information to assess risk, not to make specific track and timing forecasts.• See the following slides for additional information.• Next briefing package will be issued Thursday afternoon, August 24th• Maintain situational awareness by monitoring our website at:
http://weather.gov/phi• Contact information
Gary Szatkowski – 609-261-6602, ext. 222
National Weather ServicePhiladelphia/Mt. Holly
Things to keep in mind
• It appears less likely that the storm will track well inland over our region. Since the storm will track more over water, this enhances the threat of strong winds and coastal flooding, but may help reduce the threat of inland heavy rainfall & flooding.
• We always encourage you NOT to focus on the ‘skinny black line’ of the path forecast, since you should keep in mind forecast uncertainty.
• But we also say this because a hurricane is not a point; it covers an area. Irene is a larger than average hurricane, and that is expected to continue. This means a larger than average area of wind and rain.
National Weather ServicePhiladelphia/Mt. Holly
Hurricane Irene
• Maintain situational awareness of the latest National Hurricane Center forecast for the Hurricane at:– www.nhc.noaa.gov
National Weather ServicePhiladelphia/Mt. Holly
Our forecasts now have more detail
• Now that we are closer to the event, our forecasts have more detail– Keep in mind that it is based on the current hurricane
track forecast; as that changes, so will our forecast
• Additional details on the following slides for– Graphical forecast images
– Quick forecast
– Rainfall
– Hydrology
National Weather ServicePhiladelphia/Mt. Holly
Graphical forecast images
• The image on the left is the wind speed and direction forecast for 800 AM Sunday morning.
• You can get these and much more by going to the “Graphical Forecast Image’ selection on our web page, under the main map
• The link ishttp://www.weather.gov/forecasts/wfo/sectors/phi.php
National Weather ServicePhiladelphia/Mt. Holly
Quick Forecast – A wealth of detailThis example is for Atlantic City, NJ - Data is available for all locations
Go to the ‘Quick Forecast’ selection on our webpage Link - http://forecast.weather.gov/afm/graphical.php?site=phi
National Weather ServicePhiladelphia/Mt. Holly
Rainfall totals – we now have detailed forecast maps covering the upcoming event
• Two event total rainfall maps, side-by-side
• The one on the left was issued Tuesday evening; the one on the right was issued Wednesday morning.
• Notice the eastward shift of the heavy precipitation band, reflecting the eastward shift of the hurricane track forecast
• Red is 2+ inches; Orange 4+; Yellow is 8+, Green is 10+ inches
National Weather ServicePhiladelphia/Mt. Holly
Hydrology
• Our forecast tools which predict river response are starting to react to the expected rainfall.
• Website with this information:
http://www.erh.noaa.gov/mmefs
National Weather ServicePhiladelphia/Mt. Holly
Coastal flooding
• Coastal flooding threat will be determined by the final track and strength of the storm. There is still considerable uncertainty this far in advance.
• We will start to provide potential surge values in tomorrow’s briefing
• Regarding the astronomical tide, we are approaching the new moon on August 28th. This means the ‘normal’ high tide will be running high, worsening the potential for coastal flooding.
National Weather ServicePhiladelphia/Mt. Holly
Questions?
• If you have any questions, please contact us.
• Office 609-261-6602 x222
• Cell 609-320-7205
