HURRICANE IRMA 12 PM ET Sunday, September 10 2017 Prepared by: Keith Stellman / Kyle Thiem www.weather.gov/atlanta/briefings @NWSAtlanta www.weather.gov/atlanta
Situation Overview 11:10 AM EDT Sun Sep 10 Location: 25.0 N 81.5 W Moving: N at 9 mph Min pressure: 933 mb Max sustained: 130 mph Irma made landfall on Cudjoe Key in the lower Florida Keys at 9:10 AM as a Category 4 Hurricane. Irma is expected to move near or over the west coast of the Florida Peninsula later today through tonight. Irma should the move inland over northern Florida and southwestern Georgia Monday afternoon. IMPACTS to Georgia Sunday Night through Tuesday Time to FINISH PREPARING! Wind field has expanded and is very large. Hurricane Wind field = 100 miles wide, Tropical Storm Wind field = 360 miles wide
Watches and Warnings Expanded the TS Warning to the Northwest Added TS Watch to far North GA. The further South and West, the greater the impacts IMPACTS: Trees and powerlines with power outages common along with some flash flooding
Situation Overview Yesterday forecast Slight east adjustment with the 11 AM No significant change in the longer term for us Increases the risk for Wind Damage Flooding Tornadoes NOTE: Do not focus on the exact track. Impacts can occur well outside the area enclosed by the cone.
Possible Scenarios Model ensemble of 51 different runs Trend is to bring the storm up the Irma Tracks east side of this spread.could mean a tad weaker in S. GA *Still expect a large windfield
Wind Speed Probabilities Probabilities of Tropical Storm Force Winds slightly less for the state. Most of North GA 20-40% Extreme South Central GA 50-70%
Wind Speed Probabilities Hurricane Force Wind probabilities 5-10% far south GA Could see some slight flucations but would not expect a significant expansion northward Note: this is sustained wind probability
Time of Arrival Early/Most Likely
Worst of it comes first Model Loop Shown With precip/bands mostly on the North side of the Storm as it approaches Loop Ends at 11AM Tues Dry air coming in quickly on the southern Side clearing things out quickly as it passes
Maximum Sustained Wind 4 AM Monday 9 AM Monday
Maximum Sustained Wind 3 PM Monday 8 PM Monday
Maximum Sustained Wind 2 AM Tuesday 8 AM Tuesday
Maximum Wind Gusts (Monday) Monday 8 AM 2 PM 35-45 Highest across the South 45-55 Will be in the bands initially starting on Sunday PM in South GA 55-65 **Highly subject to change based on the speed of the storm north and the track 65-75 75+
Maximum Wind Gusts (Monday) 35-45 45-55 55-65 Monday 2 PM 8 PM Highest across the South Central GA Peak period getting into I-20 corridor **Highly subject to change based on the speed of the storm north and the track 65-75
Maximum Wind Gusts (Tuesday) Monday 8PM Tuesday 2 AM 35-45 Highest across the South Central GA 55-65 45-55 Peak period getting into I-20 corridor Increasing in North GA Mountains **Highly subject to change based on the speed of the storm north and the track
Maximum Wind Gusts (Monday) Tuesday 2 AM 8AM 30-40 Diminishing overall. Highest in the far western GA Counties 40-50 But diminishing through the morning **Highly subject to change based on the speed of the storm north and the track
Impacts Moderate Wind threat (power outages, trees downed) Flooding threat increasing Moderate/High Wind threat (power outages, trees downed) Flooding threat increasing NOTE: This is largely dependent on the track and still 2-3 days away Track through Western GA Yields max impacts from wind Highest Risk Zone Flooding/Wind (widespread trees/powerlines downed)
Expected Storm Total Rainfall Rain Mostly occurs between early Monday morning and Tuesday morning 2-3 3-5 5-7 Note: There will likely be locally higher amounts
Potential for River Flooding http://water.weather.gov/ahps2/index.php?wfo=ffc The River Forecast Center is including 72 hours of possible Rainfall in the river forecasts. Some locations go into flood as a result NOTE: These will be contingent upon the accuracy of the forecast rainfall. weather.gov/serfc We will not be issuing flood warnings based on this, but mention the flood watch.
Tornado Risk Tornado threat a little less across North GA due to stable airmass Risk greater in SE GA with bands off the coast
Comparison to Opal 4000-5000 trees downed in the Atlanta Metro ~1,200 power poles knocked down, ~5,000 snapped. ~410,000 without power at the peak 8 fatalities due to falling trees Flooding on many area rivers/creeks in NW GA
Summary Impacts could be as early as late Sunday across South/South Central GA Strong Gusty Winds in bands ahead of the main low pressure system. Downed Trees and powerlines power outages going to be the main issue Flash Flooding also possible
HURRICANE IRMA Please contact WFO Atlanta at 770-486-1133 ext 241 or through the ffcchat in NWSChat The Next Webinar Will Be: Sunday Sept 10 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