HURRICANE IRMA 12 PM ET Saturday, September 9 2017 Prepared by: Kyle Thiem / Sid King www.weather.gov/atlanta/briefings @NWSAtlanta www.weather.gov/atlanta
Situation Overview 11:00 AM EDT Sat Sep 9 Location: 22.8 N 79.8 W Moving: W at 9 mph Min pressure: 941 mb Max sustained: 110 mph Irma has weakened as it has passed over Cuba. Expected to re-intensify before landfall Continued WNW motion expected to continue over next 6-18 hours before it turns North IMPACTS to Georgia Sunday Night through Tuesday Time to FINISH PREPARING! Wind field has expanded and is very large. Hurricane Wind field = 70 miles across, Tropical Storm Wind field = 200 miles
Situation Overview Yesterday forecast Trend has been to shift west in the latter part of the forecast Keeps much of North and North/ North Central GA on the dirty side of the storm Increases the risk for Wind Damage Flooding NOTE: Do not focus on the exact track. Impacts can occur well outside the area enclosed by the cone. Tornadoes
Possible Scenarios Model ensemble of 51 different runs More confidence in a NW turn through GA Irma Tracks Does it traverse the state of FL or stay offshore longer are key factors in its intensity for N GA??
Wind Speed Probabilities Probabilities of Tropical Storm Force Winds are still increasing for the state. Most of North and North Central GA are now 30-40%... South Central GA now up to 60-90% chance of Tropical Storm Force Winds
Wind Speed Probabilities Hurricane force wind probability is confined to south GA with chances <40% Could still see some gusts approaching hurricane force well inland.
Time of Arrival earliest chance
Time of Arrival most likely
Maximum Wind Gusts (Monday) Monday 8 AM 8 PM Highest across the South Will be in the bands initially starting on Sunday PM in South GA
Maximum Wind Gusts (Overnight) Monday 8 PM Tuesday 8 AM Tropical Storm Force Wind gusts in most of GA Strongest near and NE of the eye and in rain bands Will be higher in higher elevations
Maximum Wind Gusts (Tuesday) Tuesday 8 AM Tuesday 8 PM Tropical Storm Force Wind gusts in most of GA Strongest near and NE of the eye and in rain bands Will be higher in higher elevations
Impacts Moderate Wind threat (power outages, trees downed) Flooding threat increasing Stronger winds at higher elevations Wind (some trees downed, some power outages) isolated flooding NOTE: This is largely dependent on the track and still 2-4 days away Likely bend back to the NW means greater impacts further inland Highest Risk Zone Flooding/Wind/Tornadoes (widespread trees /powerlines downed) Depending on when the westward bend occurs surge risk at the coast changes and more/less of GA at risk
Expected Storm Total Rainfall Rain Mostly occurs Mon-Wed Based on forecast Track through GA 2-3 3-5 5-8 Note: There will likely be locally higher amounts
Potential for River Flooding http://water.weather.gov/ahps2/index.php?wfo=ffc Starting later today, the River Forecast Center will include 72 hours of possible Rainfall in the river forecasts. You may start to see locations going into flood as a result NOTE: These will be contingent upon the accuracy of the forecast rainfall. We will not be issuing flood warnings based on this, but will mention in any flood watch issued.
Tornado Risk Risk for tornadoes increase in bands along and east of the track Tornadoes would be coming from East or Southeast (typically from west or southwest) Would likely be very fast moving and rain wrapped
Summary Impacts could be as early as late Sunday across South/South Central GA Impacts could extend well inland (Late Monday-> Tuesday) A Track over land is a better scenario for surge on the GA Coast, but still going to be an issue with onshore flow Increasing Tornado Risk east of the track
HURRICANE IRMA Please contact WFO Atlanta at 770-486-1133 ext 241 or through the ffcchat in NWSChat The Next Webinar Will Be: Saturday Sept 9 2017 at 8:30 PM EDT We are now giving briefings at 12 PM and 8:30 PM. Email update will be sent tonight/overnight @NWSAtlanta www.weather.gov/atlanta