UPDATE 5-Oil hits 2019-high on strong China crude use, but economic slowdown looms * Strong demand despite China GDP growth at 28-year low * OPEC-led supply cuts also support crude prices * U.S. rig count slows, output rises (Adds Brent price forecast, updates prices) SINGAPORE, Jan 21 (Reuters) - Crude prices rose to their highest so far in 2019 on Monday after data showed refinery processing in China, the world's second-largest oil consumer, climbed to a record last year despite a slowing economy.This came as prices have generally been supported by supply cuts led by the Organization of the Petroleum Exporting Countries (OPEC), analysts said. International Brent crude oil future were at $62.77 per barrel at 0726 GMT, up 7 cents, or 0.1 percent, from their last close. Brent earlier rose above $63 for the first time in 2019.U.S. West Texas Intermediate (WTI) crude futures were at $53.92 a barrel, up 12 cents, or 0.2 percent. WTI earlier advanced above $54 a barrel for