So, let me introduce you to some fundamental laws of the Emergency Department:
A day in the ED may have a certain chief complaint as an overall theme and it seems as if the majority of patients present with that complaint: Chest pain day. Abdominal pain day. Psych day. Car crash day. Corollary: Things come in threes--three code blues, three GI bleeds, three traumas.
Some ER personnel are white clouds. The day is a day that runs smoothly and everything seems to go well when those people are around. It can be anyone in any position: Doctor, nurse, patient care tech, unit secretary, doesn't matter.
Conversely, some ER personnel are black clouds--also known as "sh*t magnets"--days go poorly when these people are on duty. They attract really sick patients, complicated patients, crazy patients, drunk/drugged patients and drug seekers. If they are major black clouds they cause beds on the floors in the hospital to mysteriously disappear, consultants to cop attitudes, and machines to break.
Saying the word "quiet" will cause patients to come to the ER. Never fails. One time I went with a friend and her sister to St. Luke's on the Plaza and as we were coming in my friend's sister said, "Well, it's seems quiet." We all recoiled. Yup, it worked. While my friend was having her work up, a trauma came in and the pace picked up.
ER patients come in randomly all at once. I think they caucus on the nearest corner, although that doesn't explain the ones that come in by ambulance at the same time.
Going back to my EMT days, my favorite law of EMS is this one regarding motor vehicle crashes: If you respond to a motor vehicle crash after 0200 and there is not a drunk present, keep looking around the scene, because someone is missing.
So, if you are a patient in your local ER and you hear someone referred to as a "black cloud" you can safely assume that you might have some waiting to do. On the other hand, you know that you have someone who has lots of experience and likely knows what they are doing!