This is an entirely expected development. The current storm may well miss the Fukushima area, but at some point this hurricane season a part of a storm will move across it. TEPCO has been spraying the grounds of Fukushima Dai-ichi with a resin that should, if it operates as claimed, reduce the amount of radioactive material transported by the wind and rain. It probably works okay in a normal rain, but even cyclones that are only tropical storms can bring very heavy rainfall to an area. It won't matter if the surface is sealed when large sections of ground are washed away, as happened on Thursday night here in Vermont.
Another issue of concern is the structural integrity of the unit 4 containment building, which seems to be leaning to the right a bit. If it is seriously compromised, a big wind gust could create a crack in the spent fuel pool. TEPCO announced that it had started shoring up the structure on May 9, but I am unaware of further updates on that matter. Earlier speculation that the fuel pool had drained due damage was wrong, fortunately, but it could still happen.
On top of the existing technical problems at the site is this little incident (which will probably be resolved in a few hours, but still).
The most significant development in the Fukushima crisis over the past few weeks is the revelation from TEPCO that the fuel in units 1-3 melted down shortly after the quake and (and!) they knew it, at least for unit 1. Given that pattern of lying, and the Japanese government's servile attitude towards TEPCO, I think it's advisable to heavily discount anything they say.
Finally, this presentation by Arnie Gundersen for the Advisory Committee on Reactor Safeguards is very important for everyone to see, despite a few technical annoyances. It wasn't until a few weeks ago when he first mentioned it that I realized that the NRC assumed that there was zero probability (0.0%) that the containment structure at a nuclear reactor could fail. Containment isn't the reactor pressure vessel; failure is assumed for that, even if the probability is low. Instead, it is the larger structure built around the reactor pressure vessel. For PWRs, it is usually the entire volume of a large, circular concrete building with a domed top. For BWRs, it is usually a substructure within a large, square building, just like the ones at Fukushima. (There are exceptions to each, of course, and other types of reactors, but not in the US.) Gundersen has documented several instances where there were cracks or other penetrations in the containment at US reactors. Now, in the first real-world tests of the GE BWR Mark I containment design, there has been 100% failure. Three out of the three units that were online at Fukushima immediately prior to the earthquake and tsunami are compromised. Those results should cause the NRC put any action such as license renewal or power up-rates for the 23 operating Mk.I reactors in the US on hold until what happened at Fukushima is fully analyzed and any lessons extracted. That is unlikely to happen, unfortunately. We seem to be living in a post-fact world, where only money and power can change people's minds. The ACRS is likely to blow off Gundersen, as they have before.
ETA: Just after posting I found a report saying cooling has been restored.
Added 2011/06/01: Shoring up the unit 4 spent fuel pool started on 05/23 according to this article.