The first 30 minutes of the US cash session tell you what kind of day the market is trying to build. Here are the four classic opening types (Dalton), each with a live example from CME Nasdaq 100 futures (NQ), plus how often each one showed up in the last 22 cash sessions (23 Sep to 22 Oct, open 13:30 UTC, 5-minute bars with real exchange volume). Value areas and VWAPs on the chart come from VWAP & Volume Profile Order Flow Map [AK FlowBook].
How I classified the opens: simple rules on the first six 5-minute bars (where the open sits in the 30-minute range, where the 30-minute close finishes, and which extreme came first). Treat the counts as a guide, not gospel.
1) OPEN DRIVE (OD)
What it is: price opens and leaves in one direction right away. The open is one extreme of the first 30 minutes and price does not come back to it.
How to spot it: the open sits in the top or bottom 15% of the 30-minute range and the 30-minute close finishes in the far third.
Live example, Friday 16 Oct: open 30,023.75, first-half-hour high 30,045.75, half-hour close 29,836.75. Price never got back to the open. Day range 777 points, three times the 259-point initial balance, close 29,379.50, 644 points under the open.
Sample: 6 of 22 opens. 5 of 6 closed in the drive direction, and in 5 of 6 the starting extreme was never traded through. Average day range 332 points.
2) OPEN TEST DRIVE (OTD)
What it is: price first tests one side (often yesterday’s value edge or the overnight high or low), fails there, then drives the other way through the open.
How to spot it: the first extreme comes early, at least 20% of the 30-minute range away from the open, then the half-hour closes in the far third on the other side.
Live example, Monday 19 Oct: open 29,779, an early test up to 29,807, then a drive down to 29,683.25 by 14:00. The session closed at 29,721.75, below the open, but only after a rally to 29,983.50 in the afternoon.
Sample: 5 of 22. 4 of 5 closed in the drive direction, but in all 5 the early test extreme was traded through later in the day, and the average range was the widest of the four (421 points). The test tends to point the direction; it rarely gives a lasting extreme.
3) OPEN REJECTION REVERSE (ORR)
What it is: price moves one way, gets rejected, and comes back through the open, without the clean one-way push of a drive.
Live example, Tuesday 20 Oct: open 29,594, a drop to 29,391.75 by 13:45, back above the open by 14:00 (half-hour close 29,626.75), extension to 29,903.50 and a close at 29,687.75. The 29,391.75 low was the low of the day.
Sample: 6 of 22. In all 6 the rejected extreme held for the rest of the session and the close finished on the reversal side of the open. Average day range 397 points.
4) OPEN AUCTION (OA), in range or out of range
What it is: price rotates around the open with no initiative; both sides trade and closes land on both sides of the open.
In range = the open is inside yesterday’s range, so balance is more likely. Out of range = the open is outside it, and the market has to decide quickly whether the new prices are accepted.
Live example, Thursday 22 Oct: open 29,516, below Wednesday’s whole cash range (29,771-30,113), so an out-of-range open auction. The first half-hour just rotated 29,436-29,570 with closes on both sides of the open. The second half-hour broke it: initial balance low 29,346.75. From there it turned into a trend day down, low 29,033, close 29,146.25, cash value area 29,070-29,350 with the POC at 29,275.
Sample: 5 of 22, average range 327 points and the smallest initial balance (182 points on average). A quiet open is not the same as a quiet day, especially when the open is outside yesterday’s range.
A four-question checklist for the first 30-60 minutes
1. Where is the open: inside or outside yesterday’s range and value?
2. Does price come back through the open in the first 30 minutes?
3. How far did the first extreme get from the open before the turn?
4. When the initial balance breaks, is it in the direction of the first half-hour, or against it?
What to watch on Friday 23 Oct (cash open 13:30 UTC)
Thursday’s cash range: 29,033-29,594.75. Cash value: 29,070-29,350, POC 29,275. Overnight NQ has traded 29,042.25-29,215 since 20:00 UTC on about 43K contracts, a fraction of a cash session. An open below 29,033 is out of range under Thursday; an open back inside 29,070-29,350 makes balance more likely. My directional Nasdaq idea from Thursday (short below 29,350) gets its scored follow-up after Friday’s session.
Data: CME NQ futures, 5-minute bars (real exchange volume, no delta). Classification rules are simplified. Education, not a signal.