Date: 201812
Local time of day: 0001-0600
Location: ZZZ.Airport, US
Flight conditions: IMC
Weather elements / visibility: Thunderstorm; Turbulence
Light: Night
Aircraft: EMB ERJ 145 ER/LR
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Landing
ATC / advisory: Tower ZZZ
Reporter organization: Air Carrier
Reporter function: First Officer; Pilot Flying
Reporter qualification: Flight Crew Multiengine; Flight Crew Air Transport Pilot (ATP); Flight Crew Instrument
Human factors: Situational Awareness; Workload
Anomaly: Ground Event / Encounter Loss Of Aircraft Control; Ground Excursion Runway; Inflight Event / Encounter Weather / Turbulence
Detector: Person Flight Crew
When detected: In-flight
Result: General None Reported / Taken
Contributing factors: Human Factors; Weather
Primary problem: Weather

Narrative: During descent for arrival and approach; we had high workload under degrading IMC night weather conditions with thunderstorms; heavy rain; and moderate turbulence; coupled with change in arrival; descending at non-published to published speeds; and 3 runways changes. The last runway change was given below 10000 feet; under heavy rain; and moderate turbulence. FO (First Officer) asked CA (Captain) to set up the cockpit and brief the approach since it was below 10000 feet; and PF had to guard the controls; especially with those weather conditions. During the briefing for the approach; CA and FO had good shared mental model on the aspects of the approach and agreed to use the gust factor; having approach speed at between 140 and 145 knots with flaps 22; with winds at 360/15G25. At about 2000 feet; we were hit by lightning; under moderate turbulence. Stabilized approach with crosswind and landing with crosswind correction; within touchdown zone and standing water. After nose touchdown; airplane hydroplaned; CA came on controls to try to keep it on centerline; and told FO to get off the brakes. FO went off the controls as CA already had control of the airplane. Airplane veered off to the right side of the runway. Excursion about 20 feet off the side of the runway; coming to a stop about 50-100 feet from the 3000 foot mark. No one was injured; passengers were all in good spirits; FA did an exceptional job taking care of the passengers. Firefighters were on the scene within a few minutes; helped deplaned passengers and transfer them to a bus. After passengers and their luggage were cared for and on their way to the terminal; CA and FO did a walk around and didn't find any apparent damage to the airplane. Degrading IMC night weather; with high workload and several ATC changes in arrival and runways; under 10000 feet; in moderate turbulence. Lighting strike on final; heavy rain; gusty winds; and ceilings; all way down to 500 feet. Standing water and strong gusty crosswinds were present during touchdown.Under expected high workload and night degrading IMC weather conditions; CA and FO had good shared mental model about this arrival; approach and landing. We believed we were well prepared. Company could use training with scenario incorporating standing water; night IMC; heavy rain; gusty crosswinds; lightning strike; changing in arrivals and runways - all the threats associated with this event.




Synopsis: EMB-145 First Officer reported the flight crew lost directional control on landing roll due to workload and weather; resulting in a runway excursion.