Storm Surge TrainingStorm Surge Training

• Pre-generated 1. Parallel runs of Similar intensity storms2. Worst Case Scenario Maps

• Real-time SLOSH 3. Probabilistic storm surge (online for public)4. Real-Time SLOSH runs (NWS Only)

SLOSH Storm Surge ModelBehind the scenes

Winds 120 mphEye Diameter 25nmMoving NW 5 mph

Winds 120 mphEye Diameter 25nmMoving WNW 15 mph

• STRONGLY dependent on accurate track forecast!

• Very inaccurate more than a day in advance of landfall

• Use with extreme caution!

Realtime SLOSH Limitations

Hurricane Advisory – Approximately 12 hr. before landfall

NHC TRACK ERROR 12 hr. OUT

133 mph, 933 mb.

Rmax=25 mi(forecast)

Surge Based on NHC -12 hr. Advisory

Actual Hurricane Track 30 mi. E of -12 hr. Advisory Forecast Track

TRACK FORECAST

ACTUAL TRACK

133 mph, 933 mb.

Rmax=40 mi

Surge Based on NHC Storm Best Track

Uses an ensemble of SLOSH runs

• Intended to be used operationally so it is based on NHC’s official advisory

• Based on statistics of past performance of the advisories

• Based on size, intensity, of current and past storms rather than a random sampling

Probabilistic Storm Surge

Cross-Track Error

Other Parameters

Size: Small (30%), Medium (40%), Large (30%)

Forward Speed: Fast (30%), Medium (40%), Slow (30%)

Intensity: Strong (30%), Medium (40%), Weak (30%)

When is it Available?

• Initiated whenever a hurricane watch is issued!

• Available ~20-30 minutes after advisory release

Available Surge Products

ProbabilisticProbabilistic: This graphic shows the overall chance that storm surges will be greater than x feet above normal tide levels during the next 3 days.

Exceedance: Exceedance: This experimental graphic shows storm surge heights, in feet above normal tide level, which have a x percent chance of being exceeded during the next 3 days.

 

Rmax=25 mi(forecast)

Surge Based on NHC -12 hr. Advisory

Deterministic SLOSH run shows limited surge threat to Pensacola area

Actual storm caused highest surge in Pensacola area

Probabilistic product shows considerable surge threat to Pensacola area

Questions???