[ by Melanie Gretchen and Howard Haykin ] Estimates that JPMorgan Chase's trading loss can reach $9 billion have caught many Wall Street professionals, regulators, and investors by surprise.  Previous estimates had placed the losses in the range of $2 billion (the initial estimate) to the more recent estimate of $5 billion.  In reaction to the rumors, trading in JPMorgan stock has been brisk, with shares down more than 5% from Wednesday's close. It's believed that the sudden large increase in loss estimates can be attributed to the manner in which JPM is unwinding the positions accumulated by the Chief Investment Office in London.  The bank has been rapidly unwinding its positions and quantifying its losses much faster than many had expected, with particular attention to closing out the most volatile positions.  Bank internal models, that analyze realized gains and losses on closed out positions, recently projected that losses could run as high as $8 billion or $9 billion. Yet, with much of the most volatile positions off the books, regulators are unsure how deep the reported losses will eventually be, and some do not expect the losses to exceed $6 billion or $7 billion. Status Update. Since senior managers faced the initial worst-case scenario figure of $9 billion, estimates have leveled out at somewhere between about $4 billion and $6 billion, according to two people familiar with the matter. No exact number has yet been provided by JPMorgan executives, though CEO Jamie Dimon has said the results of the bank's second quarter, which ends Saturday, will be "solidly profitable."  Someone familiar with his thinking has speculated that his expectations would be in line with the bank's recent quarter profits of $3.5 billion and $5 billion. Outside the firm, analysts have set their expectations for the firm at $22.4 billion in revenue for this quarter and about $3.5 billion in net income, assuming trading losses that the CEO has publicly estimated at more than $2 billion, according to Thomson.  Other potential boots to the firm's final numbers include improvements in the housing market, which have resulted in loss-reserve reductions and debt-valuation adjustments (enabling paper profits when banks' credit-quality declines). For further details, go to:  [CNBC: "JPM Loss .. $9Bn, .. Likely to be Less", 6/28/12] and  [Dealbook: "JPMorgan Trading .. Reach $9Bn", 6/28/12].