In both Exodus and Nehemiah 9:12 the cloud seems to be a pillar in front of the people but Psalm 105:39 seems to indicate that the cloud traveled above them. Were there two clouds or am I misunderstanding the image?:
JPS Tanakh 1917 Psalm 105:39 He spread a cloud for a screen; And fire to give light in the night.
I find the idea of a cloud overhead very reasonable but the picture elsewhere seems to be pretty clear that it was a pillar of cloud in front of them:
JPS Tanakh 1917 Exodus 13:21 And the LORD went before them by day in a pillar of cloud, to lead them the way; and by night in a pillar of fire, to give them light; that they might go by day and by night:
The account in Numbers 9 seems a bit ambiguous to me:
15And on the day that the tabernacle was reared up the cloud covered the tabernacle, even the tent of the testimony; and at even there was upon the tabernacle as it were the appearance of fire, until morning. 16So it was alway: the cloud covered it, and the appearance of fire by night. 17And whenever the cloud was taken up from over the Tent, then after that the children of Israel journeyed; and in the place where the cloud abode, there the children of Israel encamped. 18At the commandment of the LORD the children of Israel journeyed, and at the commandment of the LORD they encamped: as long as the cloud abode upon the tabernacle they remained encamped. 19And when the cloud tarried upon the tabernacle many days, then the children of Israel kept the charge of the LORD, and journeyed not. 20And sometimes the cloud was a few days upon the tabernacle; according to the commandment of the LORD they remained encamped, and according to the commandment of the LORD they journeyed. 21And sometimes the cloud was from evening until morning; and when the cloud was taken up in the morning, they journeyed; or if it continued by day and by night, when the cloud was taken up, they journeyed. 22Whether it were two days, or a month, or a year, that the cloud tarried upon the tabernacle, abiding thereon, the children of Israel remained encamped, and journeyed not; but when it was taken up, they journeyed. 23At the commandment of the LORD they encamped, and at the commandment of the LORD they journeyed; they kept the charge of the LORD, at the commandment of the LORD by the hand of Moses. THE HOLY SCRIPTURES ACCORDING TO THE MASORETIC TEXT A NEW TRANSLATION Jewish Publication Society 1917
I'm having a hard time getting a consistent picture in my mind of what was going on.