DUBAI, May 23 (Reuters) - Stock markets in the Gulf face further downward pressure on Monday after oil prices weakened and as trading volumes shrink ahead of the holy month of Ramadan and the summer holidays.

Brent oil LCOc1 is down 0.5 percent to $48.50 a barrel in Asian trade on a strong U.S. dollar and signs that global crude supply is holding up despite unplanned outages increasing to at least five-year highs. O/R

Local day traders have been leading the stock markets lower since the end of last week, cashing out ahead of Ramadan, which historically sees low volumes in some markets.

On Sunday Dubai's index .DFMGI confirmed a break below technical support on the late March and early May lows of 3,248-3,256 points. That triggered a bearish head & shoulders pattern formed by the highs and lows since March and pointing down to the 2,800-point area.

Saudi Arabia's bourse .TASI has also been slipping, pulled down by petrochemical shares which had outperformed over the last month. But some investors are allocating funds to beaten-down retail industry shares.

Retailers Jarir Marketing 4190.SE and Fawaz Alhokair 4240.SE are up 1.7 percent and 25.5 percent since last week.

(Reporting by Celine Aswad; Editing by Andrew Torchia) ((celine.aswad@thomsonreuters.com; +971 4 4536886; Reuters Messaging: celine.aswad.thomsonreuters.com@reuters.net))