Large Transport
Flight Crew Last 90 Days 120; Flight Crew Total 10000; Flight Crew Type 4500
Confusion; Human-Machine Interface
Deviation - Track / Heading All Types; Deviation / Discrepancy - Procedural Clearance; Inflight Event / Encounter Weather / Turbulence
Air Traffic Control Issued New Clearance; Flight Crew Became Reoriented
Human Factors
We departed Runway 8 at DEN.  Thunderstorms were blocking the Yellowstone Departure with the HANKI transition.  This was our filed route.  We were given a heading to fly after departing Runway 8.  The heading was keeping us south of the weather.  After climbing past the storms; we were given a revised route.  Direct HCT direct FOD as filed.  I had the autopilot on.  I quickly entered what I thought was the correct course into the FMC.  Mistakenly entering HYS; which is Hays; Kansas; instead of entering HCT Hays Center; then FOD.  It looked reasonable on the display.  The direction; distance; and letters (HYS).  So; we agreed and I executed the route.  The Captain then informed Dispatch of the route change.  After flying for a few minutes; ATC asked us if we were now turning direct (HCT)? We replied we were.  They then cleared us direct FOD.  After wondering why they asked us this; we realized I had entered HYS for HCT.  HYS was about 25 to 30 degrees further south of HCT.  We didn't confirm HCT off the Chart because at the time we only had our filed departure procedure; the Yellowstone HANKI transition; out.  HCT was not on this chart.  Also; like I said; the letters HYS; HCT; Name Hays; Hays Center; distance; and heading all seemed reasonable.  Also; we were distracted by the weather and informing dispatch of the new route of flight.
After departing DEN on Runway 8; we were on a 090 heading for TRWs that blocked our Yellowstone HANKI Departure. Had requested Direct ONL as filed; but DEN Center later gave us direct Hayes Center; Fort Dodge; as filed.  We entered into the FMC; HYS; FOD. It should of been HCT; FOD.  After a moment center asked if we are direct Hayes Center yet?  We all realized our mistake and DEN center recleared us FOD as filed.  No comments were made by DEN Center and no traffic was displayed within 40 miles on our TCAS.
Air carrier flight crew is vectored around thunderstorms during departure then cleared direct Hays Center; direct Fort Dodge; FPR.  HYS is mistakenly entered for HCT resulting in ATC questioning the route and issuing a revised clearance.