EC145
Flight Crew Last 90 Days 100; Flight Crew Total 3000; Flight Crew Type 500
Time Pressure; Workload; Human-Machine Interface; Situational Awareness; Distraction
Deviation / Discrepancy - Procedural Published Material / Policy
General None Reported / Taken
Environment - Non Weather Related; Human Factors; Weather; Procedure
While waiting on hospital roof for patient and medical crew; I noticed visibility decreasing with storms to the north and south of our route of flight; both moving East.  I texted the crew still in the hospital that 'we need to get going.'  Admittedly; I was in a hurry.  I used the rotor brake on shut down; staying in the cockpit for NVG security.  Once the crew arrived I started the run up; I did not brighten the CAD as I normally do; missing the Rotor Brake Caution warning.  I ran the throttles to FLY and didn't notice the warning until my before take off check.  TOO LATE!  I learned several lessons.  Always use the check list especially in a dark cockpit.  Don't let weather/patient status get me in a rush.  Leave my hand on the rotor brake lever until returning it to the down position. Brighten the CAD (as I usually do) BEFORE any other step. No excuses; just stupidity and being human I guess.
EC145 pilot; concerned about weather and the need to expedite departure; failed to note that the main rotor brake was engaged until after the throttles had been advanced for takeoff.