Narrative:

When we leveled off at FL370 and noticed an amber IAS indication. When we checked the airspeed indicators we noticed that the first officer's airspeed was indicating lower than mine and the standby airspeed indicator. As we accelerated there was no change in his airspeed indicator. Based on this I thought there was a blockage of pitot tube 2. The pm pulled out the QRH and it instructed us to do an air data computer (air data computer) reversion. This also required us to descend out of rvsm airspace. ATC assigned us FL270 and we began to descend. We descended with the autopilot on. As we descended we noticed the standby IAS and captain side no longer matched up. Captain side IAS was descending and acting like an altimeter. This caused some uncertainty initially as we were not sure which one to believe. We were asked to increase our descent by ATC so I increased the vs to 2000 fpm. Shortly after this the airplane did an uncommanded pitch down and we disconnected the autopilot. It was at this point smoke or water vapor came pouring in through the window seals. I wasn't sure which it was at first; but it made me worried about our pressurization and we were still at FL300 and hand flying. I checked the cabin pressure on the EICAS and it seemed normal. About at this point we also experienced a failure of both adcs as we got red xs across our instruments. I also saw an ic-600 failure message on the EICAS and the first officer reported seeing a presn auto fail message. We [advised ATC] and proceeded to ZZZ. We received radar vectors there. As we descended the systems came back online and by the time we were getting vectors to ILS all indications were normal again. At some point I turned the autopilot back on but it kicked off after we intercepted the localizer as the localizer was swaying back and forth. After that we landed uneventfully at ZZZ.bad weather; instrument failure; task saturation. The autopilot pitch down was caused by me leaving the autopilot on after I should have disconnected it. At the time I was busy and it did not occur to me that I should turn the autopilot off. At that time I was busy trying to decide which airspeed indication I could rely on and trying to figure out what was going on.

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Original NASA ASRS Text

Title: EMB145 flight crew reported an airspeed indication failure at FL370 in IMC with thunderstorms nearby. The flight diverted to the nearest suitable airport with airspeed returning to normal during the approach.

Narrative: When we leveled off at FL370 and noticed an amber IAS indication. When we checked the airspeed indicators we noticed that the FO's airspeed was indicating lower than mine and the standby airspeed indicator. As we accelerated there was no change in his airspeed indicator. Based on this I thought there was a blockage of pitot tube 2. The PM pulled out the QRH and it instructed us to do an ADC (Air Data Computer) reversion. This also required us to descend out of RVSM airspace. ATC assigned us FL270 and we began to descend. We descended with the autopilot on. As we descended we noticed the standby IAS and Captain side no longer matched up. Captain side IAS was descending and acting like an altimeter. This caused some uncertainty initially as we were not sure which one to believe. We were asked to increase our descent by ATC so I increased the VS to 2000 fpm. Shortly after this the airplane did an uncommanded pitch down and we disconnected the autopilot. It was at this point smoke or water vapor came pouring in through the window seals. I wasn't sure which it was at first; but it made me worried about our pressurization and we were still at FL300 and hand flying. I checked the cabin pressure on the EICAS and it seemed normal. About at this point we also experienced a failure of both ADCs as we got red Xs across our instruments. I also saw an IC-600 failure message on the EICAS and the first officer reported seeing a PRESN auto fail message. We [advised ATC] and proceeded to ZZZ. We received radar vectors there. As we descended the systems came back online and by the time we were getting vectors to ILS all indications were normal again. At some point I turned the autopilot back on but it kicked off after we intercepted the localizer as the localizer was swaying back and forth. After that we landed uneventfully at ZZZ.Bad weather; instrument failure; task saturation. The autopilot pitch down was caused by me leaving the autopilot on after I should have disconnected it. At the time I was busy and it did not occur to me that I should turn the autopilot off. At that time I was busy trying to decide which airspeed indication I could rely on and trying to figure out what was going on.

Data retrieved from NASA's ASRS site and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.