My understanding is that "contango", when describing the forward curve, describes forward prices that are above the current spot price, i.e. $F_{t+1} > F_{t} > S$. This is directly observable at the current time.
"Normal backwardation" is the phenomenon that the current forward price is below the expected spot price at expiry. I understand this can happen when speculators go net long and expect a profit (i.e. expect a premium to take on the risk by the hedger).
However, my understanding is these two can happen simultaneously. Due to carrying costs, etc. a forward curve is often in contango. I expect this when the convenience yield is less than the cost of carry.
I would also expect that simultaneously, most futures would exhibit "normal backwardation". due to the above reasoning regarding risk premium for speculators.
My question is: how can both be true simultaneously? A forward curve in contango seems to imply to me that the future has negative theta, i.e. decays to expiry. However, normal backwardation seems to imply to me that it is positive theta, i.e. will rise to meet the spot at its (higher) expected value.