THE cost of living in Hong Kong jumped sharply in October, as the disruption and flooding which followed Typhoon Dot at the end of September sent food prices soaring. All measures of inflation increased, driven by hefty rises in the price of food in the shops and market. The year on year rise in Consumer Price Index (A) jumped nine per cent compared with the same month last year, the CPI 'B' rose to 8.7 per cent, while the Hang Seng CPI was 9.4 per cent higher. The across the board rises reversed the slow-down in the previous month's figures, when the CPI (A) was up 7.9 per cent, the CPI (B) rose 8.1 per cent and the Hang Seng CPI by 9.2 per cent. The Government had already warned that the price of food was rising early last month, and this was borne out by the size of the increases of the food component in all the indexes. Food prices in the CPI (A) leaped 10.5 per cent, and a government spokesman put the blame on the rise in the cost of fresh vegetables. The Hang Seng CPI, which measures the expenditure of Hong Kong's better off, jumped 8.5 per cent, with fresh shrimps, crabs, live poultry, tinned meats, processed fruits, edible oils and beancurd all costing shoppers more. This month the better weather is expected to see prices resuming their downtrend, and economists said yesterday that the Government's target of a nine per cent inflation rate this year looked safe. ''There is no cause for alarm,'' commented Jim Wong, economist with the Hong Kong and Shanghai Bank, ''if you look at this month's food prices, it has settled down again.'' Daryl Ho, economist with Jardine Fleming agreed that the blip represented no danger to the slowing trend in price rises. ''If you exclude food and fuel, which were hit by the weather, the core inflation in the CPI (A) is 8.9 per cent, down from 9.1 per cent last month.'' There was still concern that the absolute rate of inflation remained too high - it is the second highest in the region behind China and Indonesia - and could be starting to erode Hong Kong's competitive position. But economists detect a slowing in wage push inflation as salaries in Hong Kong begin to reflect the lower wages paid in Guangdong, and manufacturers here steadily shed jobs. Mr Ho said Jardine's forecast for inflation next year was eight per cent, while this year he believed the Government's forecast of nine per cent would prove too pessimistic, and suggested that 8.5 per cent would be the final figure. This is in line with the 8.5 per cent average at which the CPI (A) has been rising over the last three months. But while core inflation was still shrinking, it was despite some accelerating price rises apart from food last month. Housing was up 11 per cent in the CPI (A) and CPI (B), alcoholic beverages rose 10.5 per cent over the year in the CPI (A) and 9.8 per cent in the CPI (B). Costs in the upper end of the housing market as measured by the Hang Seng housing index also climbed, by a sharp 13.6 per cent year on year. The gain on the month was 1.1 per cent. There was also an end to a lot of the bargains in the department stores. As clearance sales came to an end, and price tags returned to normal, the Hang Seng Index for clothing and footwear jumped 3.1 per cent. Prices for Chinese newspapers, soft furnishings and household cleansing supplies, as measured by the index, rose 1.1 per cent.