B737-700
Flight Crew Air Transport Pilot (ATP); Flight Crew Instrument; Flight Crew Multiengine
Flight Crew Last 90 Days 412; Flight Crew Type 412
Communication Breakdown; Situational Awareness; Confusion
Deviation / Discrepancy - Procedural Published Material / Policy; Inflight Event / Encounter Weather / Turbulence
Flight Crew Became Reoriented
Manuals; Human Factors; Weather
On climb out; passing about 25;000 feet with a [temperature] of about -4; we picked up enough ice to almost completely obscure the forward window. I sent an ACARS Flight Ops report message to Dispatch for 'heavy ice.' Dispatch sent back a message that we needed to use the terms 'moderate' or 'severe' as 'heavy' was not a term used as a PIREP. Knowing 'severe' would have a major operational impact on our system; I wanted to make sure I was following the correct narrative; so I opened the AIM I had downloaded in ForeFlight. 'Severe' icing was described as an accumulation rate that exceeded the ability of the aircraft's systems. As we had placed the engine and wing ice on; I had looked outside to see if we were getting the leading edge clear and it appears we were. To be honest; I'd never seen such icing buildup in [many] years of flying and while I thought we could handle it; I was worried about other aircraft with deicing boots or military aircraft with no wing deicing. This left me with the question; in reality; when would a 737NG ever experience the true definition of severe icing? If we did; could we tell? The side windows give very limited visibility to the wing and if we had ice buildup aft of the leading edge; could we tell from the cockpit? I had my doubts. What about our ice accumulation on the vertical and horizontal stabs? If our engine and wing icing could deal with this level of ice accumulation; would there be any level they couldn't handle? I ended up reporting 'moderate' icing since that seemed to correspond to the AIM definition that we had. Still; for some reason the experience left me a little worried that something in our guidance may be missing.
B737NG Captain reported encountering icing conditions obscuring the forward window that raised concerns to a crew's ability to discriminate between icing intensity level definitions.