The weather vane of Middle East peace prospects blows so erratically that caution is always in order in forecasting the climate, be it good or bad. Yet, in the interest of encouraging a momentum toward negotiation, several positive signs of late deserve mention. They do not add up to a breakthrough yet, but they offer a glimmer of hope for getting an Israeli-Arab negotiation rolling.
There are, for instance, growing indications that King Hussein of Jordan may soon announce his readiness to join peace talks, provided Israel offers some gesture such as a freeze on West Bank settlements. The PLO, for its part, appears to be moving toward acquiescing in a negotiating role for Jordan. Iraq, meantime, now hints at Israel's need for security, suggesting it would be supportive of King Hussein's involvement.
Then there is the interesting fact that the first official contact is reported underway between Israel and the PLO. Not too much significance should be attached to this development. The contacts (said to be taking place in Austria) have the limited aim of freeing eight Israeli soldiers taken prisoner by the PLO in Lebanon in exchange for PLO fighters held captive by Israel. Yet the Israeli government has not issued a denial, as it did in the case of indirect talks in the past. Israeli Foreign Ministry officials in fact are reportedly carrying on the negotiations.
Could these contacts expand to include the broader issue of peace? The Begin government has consistently maintained that it will have nothing to do with the Palestine Liberation Organization, that the PLO guerrillas are not ''fighters'' but ''terrorists.'' Yet Israeli actions belie the thesis and show the untenability of that position. Israel, after all, invaded Lebanon - not an act of war against the Lebanese but against the Palestinian guerrillas there. This was an Israeli-Palestinian war, and under the Geneva Convention Israel is obligated to talk with the PLO about war-related matters. Even before last summer's invasion, the Israeli authorities consistently treated captured PLO guerrillas as prisoners of war and not political prisoners.
All of which is to say that the chances for resolution of the Palestinian problem would be greatly enhanced if the government of Menachem Begin talked directly with the PLO concerning a negotiated settlement. The Israeli prime minister could heed the lesson of Israel's own past advice to others. For years the Israeli government upbraided the Arabs for not sitting down for face-to-face talks with Israel. ''Let's just meet in a room together,'' the persuasive line went, ''and we'll settle this thing ourselves.'' Egypt finally broke through Arab hesitance and the result was the signing of a peace treaty and recovery of its territory.
Now the shoe is on the other foot. Will Israel practice what it preaches? Mr. Begin could startle the world no less than did President Sadat if he recognized in public what his actions in private concede: the objective existence of the PLO and therefore in effect the legitimacy of dealing with it. Israel's Old Testament history is replete with instances of talking with the ''enemy,'' so tradition should be no barrier.
In any case, the opportunity for progress does seem to be widening in a number of directions. Yes, the obstacles continue to loom large - the withdrawal of foreign troops from Lebanon, the unrelenting Israeli squeeze on the West Bank, the anxieties of both Jews and Arabs about where peace talks might lead. It will take more firmness from Washington than is so far evident to bring President Reagan's peace initiative to fruition. But there are some signs of forward movement - and that is not a bad way to begin 1983.