** Shares of natural gas companies rise as natgas futures jump about 5% to a 23-month high NGA/

** U.S. natgas prices NGc1 up 4.3% at $3.74 per mln British thermal units (mmBtu) on early forecasts for much colder weather in mid-January that could freeze oil and gas wells and lift spot prices by reducing output as in past years

** LNG firms - NextDecade NEXT.O up 5.6%, CNX Resources CNX.N up 2.3%, Energy Transfer ET.N up 2.4% and New Fortress NFE.O up 6.6%

** ETFs United States Natural Gas Fund UNG.P rises 2.3% and ProShares Ultra Bloomberg Natural Gas BOIL.P up 3.4%

(Reporting by Pooja Menon in Bengaluru)

((Pooja.Menon@thomsonreuters.com;))