| Note ID | Start Time (US/Mountain) | End Time (US/Mountain) | Entrant | Note |
| 28305 |
17 Sep 2023 @ 1345 |
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SantaFe108 |
Calm, flat pool. Tiny bit of overflow down front of mound. |
| 28178 |
10 Sep 2023 @ 0733 |
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SantaFe108 |
Flat pool, barely overflowing down front of mound. |
| 27957 |
02 Sep 2023 @ 1820 |
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SantaFe108 |
Full and calm, barely overflowing down front of mound. |
| 27022 |
12 Jul 2023 @ 1637 |
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minissa |
I didn't know if this was new or not, but it's new for us. Not a speck of steam from the vent on a warm day, but the whole front of the formation is wet in what looks like runoff channels. Cyanobacteria around vent is orange but not extensive, maybe a few inches to the right and forward of the vent. Could it have erupted or had some sort of hot period? |
| 25441 |
14 May 2023 @ 1810 |
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User34 |
Full and bubbling |
| 21696 |
03 Jun 2022 @ 1851 |
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Stephen_Gemar |
Appears to be below overflow. Whistle had slight recent overflow- water trickled about midway down the front of Whistle’s embankment. |
| 18300 |
06 Jul 2021 @ 1505 |
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User34 |
Overflowing and bubbling slightly |
| 17427 |
04 Jun 2021 @ 0946 |
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Stephen_Gemar |
Pool appears to have dropped from my earlier observation. Infrequent light bubbling observed at this time. |
| 17426 |
04 Jun 2021 @ 0916 |
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Stephen_Gemar |
Pool is overflowing, with light bubbling. Overflow is still light, but runoff has flown far down the front side of Whistle, to within fifteen feet of the trees by the road. |
| 17404 |
03 Jun 2021 @ 1015 |
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Stephen_Gemar |
Whistle’s runoff is much dryer compared to last observation. The pool appears to be below the level it was at a couple of days ago. The top-middle portion of its runoff is still white-orange. |
| 17316 |
31 May 2021 @ 1905 |
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Stephen_Gemar |
Whistle is hot enough to have turned part of its runoff channel white-orange. Some occasional light bubbling seen. Overflow still appears to be light, but enough to overflow its main runoff channel. |
| 14655 |
17 Jun 2020 @ 1110 |
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Janet Jones |
Overflowing and bubbles making 1” splashes. |
| 762 |
18 Jul 1991 @ 0000 |
18 Jul 1991 @ 2359 |
geysergaze |
Observed NS from Old Faithful Overpass. water phase lasted over four minutes, which is very long historically. Most water phases last about a minute. |
| 19758 |
12 May 1991 @ 0000 |
24 May 1991 @ 0000 |
mhreed |
From the July–August 1991 Sput (Vol. 5 No. 4): "...it was realized by [Rocco] Paperiello and [Mike] Keller that deep runoff channels marked Whistle's cone, showing that an eruption must have occurred between May 12 and 24."
In a post to the geyser listserv dated 1997/01/12, Paperiello writes: "As to the May eruption, I was keeping an eye on Whistle in 1991, and have the eruption in May down to between the 12th and the 18th, assuming that it takes 2 1/2 days to again reach overflow after an eruption." |