Citibank has issued a warning that Bitcoin's recent weak trading patterns could indicate a potential downturn for the Nasdaq 100 index. Historically, Bitcoin's performance has been closely linked to the Nasdaq, with the index's returns improving significantly when Bitcoin trades above its 55-day moving average. Currently, Bitcoin has fallen below this threshold, coinciding with a decline in risk-adjusted returns for the stock market. Analysts attribute the weakness in the crypto market to tightening liquidity, noting that bank reserves have decreased by approximately $500 billion since mid-July, reducing market liquidity. However, the report also highlights that the Treasury's balance is nearing the bottom of its replenishment cycle, suggesting that liquidity could soon improve, potentially boosting both Bitcoin and stock market performance.