Date: 201812
Local time of day: 0001-0600
Location: ZZZ.Airport, US
Weather elements / visibility: Turbulence
Aircraft: B737-800
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Initial Climb; Takeoff / Launch
Airspace: Class B ZZZ
ATC / advisory: Tower ZZZ
Reporter organization: Air Carrier
Reporter function: Flight Attendant (On Duty)
Reporter qualification: Flight Attendant Current
Human factors: Situational Awareness; Confusion; Communication Breakdown
Second reporter function: Flight Attendant In Charge
Anomaly: Deviation / Discrepancy - Procedural Published Material / Policy; Flight Deck / Cabin / Aircraft Event Other / Unknown; Inflight Event / Encounter Weather / Turbulence
Detector: Person Flight Attendant
When detected: In-flight
Result: Flight Crew Became Reoriented; General Physical Injury / Incapacitation
Contributing factors: Human Factors; Weather
Primary problem: Weather

Narrative: Weather in ZZZ. 3 hour delay with mechanical issues and airport closed sporadically due to storms. Captain announced we would be at least 30 more mins before departure. Flight attendants used the delay kit and served water. Then Captain announced we were going to be released to go in 10 or 15 minutes. Flight Attendant 3 called cockpit to say we had a pax in the lav. [Flight attendants] #1;2;3 started a quick pickup of service items when all of a sudden we were taking off! [Flight attendants] #1;3 flew to try to get to their jump seats. [Flight Attendant] #2; me; was mid main cabin and heading aft when the pax exited the lav. With no clear path to my jumpseat; I sat down on the floor and told the pax to sit down on the floor as well and hang onto the armrest. We sat there for probably 5 mins and when there was a slight break in turbulence; we headed to the last row. Made it to the last row where we had a young unaccompanied minor who was frightened; so I sat down beside her. Gripping the armrest; we were bounced up and down and sideways in severe turbulence. We were actually lifted off of the seats. Passengers were screaming and praying out loud. Captain denied getting a phone call about the pax in the lav and no comment on the quick takeoff with no warning for the crew. He asked several times on the way to the hotel if we all had our stories straight....meaning were we and the cockpit going to tell the same story. It was severe cabin turbulence with articles flying and pax being lifted from their seats. Captain stated that in the cockpit it was moderate turbulence. It is my belief that we never should have been released for takeoff. The turbulence started the minute our wheels left the tarmac. Unsafe. Possible reasons - pilots were close to timing out and Captain commented that we were running low on the quantity of fuel needed for the flight to [destination airport] - stating this was the reason we shut down one engine while waiting. Captain appeared to be much more concerned about the takeoff and the Flight Attendant situation than he was about the turbulence.


Second narrative: After boarding started when the ramp was finally open and everyone was in their seats; the pilots informed us we had a maintenance issue and since the ramp just closed again; it was going to be a while till they showed up. After two long hours; we finally closed the door. We finally get pushed back and on our way to the runaway. The runway then closed and open and closed and open. I decided at the point to inform the pilot that we had to do the tarmac delay kit. At this point; people had been on this plane for 5 hours and it just wasn't fair to them. He says okay I will get back to you when the runway reopens try to do the delay kit quickly. Communication started heading south when the Captain called back and informed us that they had a very small window before 'Turning into pumpkins' and they were going to take the opening. At this point; we were done with the service and picking up; he came over the intercom and told us we were number three for take-off and it was going to be around 10 minutes. Literally no more than a minute later; were going full force down the runway about to take off. I didn't hear the prepare [announcement] and neither did the other 3 flight attendants. Not only was I running in to my jumpseat with the front wheels already off the ground; my number three was also in the aisle trying to make to her jumpseat. Finally after making [it] to my jumpseat; I looked in the aisle to see if everyone was okay only to notice a passenger on the ground in the aisle. I called to back and told the [Flight Attendant] 4 to tell the passenger to try to make it to any available seat near him and she informed me the Flight Attendant was on the ground with him.  At that moment I told the [Flight Attendant] 4 to try to get them in a seat immediately. They got to a seat then the extreme turbulence happened. People were bouncing around the like rag dolls swaying from left to right/ up and down. The three and I lifted from our seats anywhere from 3-5 inches off our jump seats. I could hear some people in First Class praying. Luckily; we had the harness on or we would have hit the ceiling no doubt. After all was said and done; he called to see if we were ok. I said I think so; only to find out the number 3 was injured. She can hardly move her head or lift her arms. She went to urgent care and is now off the trip. Better communication [is needed].


Synopsis: Three Flight Attendants reported severe turbulence on departure and an injury to one of the Flight Attendant.