Intraday Regime

A daily regime classification (bull, bear, sideways) answers: what is the market doing over weeks and months? An intraday regime answers: what is the market doing right now, in the current session? These can diverge significantly. A broad bull market can have intensely choppy intraday sessions on Fed days, opex weeks, or low-volume summer Fridays. Conversely, a bearish month can contain trending intraday sessions driven by sector rotation or macro catalysts. Intraday regime matters most for day traders because strategy selection and sizing decisions happen on a session-by-session, sometimes hour-by-hour basis. Applying momentum strategies during a choppy intraday session is one of the most common sources of whipsaw losses.

The efficiency ratio (ER) quantifies how 'efficiently' price moves in one direction. It is calculated as: ER = |Net displacement| / Total path length. Over a 12-period rolling window on 5-minute SPY bars (one hour of data), an ER above 0.35–0.40 indicates trending conditions where price is making directional progress. An ER below 0.25–0.30 indicates choppy conditions where oscillations cancel each other out. The ER responds quickly to regime shifts — a gap and strong directional move creates a high ER immediately, while a reversal to random oscillation drops the ER within 2–3 bars. This responsiveness makes it superior to lagging indicators like ADX for intraday regime classification.

Trending intraday regime: momentum breakout strategies (ORB, VWAP cross, range expansion) have edge. Entries should be made on breakouts from consolidation, and trailing stops can be held wider to let the trend run. Positions initiated in trending regimes are often extended toward maximum hold time rather than closed early. Choppy intraday regime: mean-reversion strategies (VWAP bounce, oversold reversals, range fades) outperform. Momentum breakout entries are penalized or blocked entirely. Positions should target modest, quick gains and exit before the oscillation reverses. Regime-aware strategy selection is consistently shown in academic literature to improve risk-adjusted returns by 15–35% compared to static strategy deployment.

The most critical use of intraday regime detection is managing open positions when the regime shifts. A trending-to-choppy flip while holding a momentum long position signals that the tailwind driving the trade has dissipated. Continuing to hold the position now involves mean-reversion risk — the very condition the momentum entry was not designed for. Tradewink triggers an AI bull/bear debate when this regime flip occurs with an open position, weighing the remaining profit buffer, MFE already captured, and time remaining in the session to decide whether to exit, tighten stops, or hold. This automated regime-shift exit protocol prevents large winners from being fully given back when intraday conditions deteriorate.