Rav Pinhas Zevihi (contemporary), in his work Ateret Paz (229), records an ancient custom to make a special announcement in the synagogue on the night preceding the day of Birkat Ha’hama, the blessing recited every twenty-eight years when the sun returns to its original position. The announcement should remind people about the Beracha to be recited the next day, and that the prayer service will be held at Netz Ha’hama (sunrise), as is customary on the day when this Beracha is recited. This custom is mentioned by the Magen Abraham (229:5), in the name of the Maharil. Rav Zevihi advocates following this custom to ensure that people remember to arise early the next morning to recite Shaharit at sunrise (listen to audio recording for precise citation).
If a person does not, for whatever reason, pray Shaharit at sunrise on the morning of Birkat Ha’hama, should he recite the Beracha as soon as he sees the sun, or should he wait until after he recites Shaharit?
Rav Zevihi writes that a person in this case should recite Birkat Ha’hama immediately upon seeing the sun, rather than delaying the recitation until after Shaharit. The famous Halachic principle of "Zerizin Makdimin Le’misvot" establishes that one should perform Misvot at the first opportunity to do so, and therefore one should not delay the recitation of Birkat Ha’hama. Rav Zevihi adds, however, that a person should first recite Birkat Ha’Torah (the Beracha recited each morning before studying Torah) before reciting Birkat Ha’hama. The recitation of Birkat Ha’hama is customarily accompanied by the recitation of a series of verses and chapters of Tehillim, which one may not recite before reciting Birkat Ha’Torah. One should therefore recite Birkat Ha’Torah before reciting Birkat Ha’hama, so that he could recite as well all the accompanying texts.
This is also the ruling of Hacham Ovadia Yosef, both in Yehave Da’at (vol. 4, 18:3) and in Halichot Olam (Parashat Ekeb, 9, p. 190).
Summary: On the night before Birkat Ha’hama, it is appropriate to make an announcement in the synagogue reminding people of this Misva. Although it is generally customary to recite Shaharit at sunrise and then recite Birkat Ha’hama after Shaharit, one who sees the sun before Shaharit should recite Birkat Ha’hama. He should preferably recite Birkat Ha’Torah before Birkat Ha’hama, so that he could also recite the accompanying verses and chapters of Tehillim.