Tropical Storm Pena was spinning at 40 mph about 685 miles southwest of South Point, Hawaii, at 5 p.m. HST on Nov. 9, and the Central Pacific Hurricane Center is no longer calling for it to strengthen. Forecasters were projecting a minimal hurricane just two days earlier. Their latest discussions say a mix of wind shear and dry air could leave it as a remnant low, or dissipate it outright, within a couple of days.
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From a forecast hurricane to a ragged tropical storm
When Pena formed on Nov. 6, about 650 miles south-southeast of South Point, the outlook was bullish. The Honolulu Star-Advertiser reported that the 5 p.m. forecast that evening called for about 60 mph by early Saturday, 70 mph by early Sunday and 75 mph by Tuesday, with model guidance ranging from a strong tropical storm to a Category 2 hurricane. By Nov. 7 the paper said forecasters expected a minimal hurricane by Wednesday.
That never materialized. In Discussion 13, issued at 11 a.m. HST on Nov. 9, forecaster Mahoney kept Pena at 35 knots, or 40 mph, while adding that the estimate could be generous. The low-level center sat west of the convection, and the circulation looked open on its western side, which is a sign of a system struggling to hold itself together.
The storm did intensify at first. By 11 p.m. HST on Nov. 6 its winds had risen to 50 mph, and at 5 p.m. on Nov. 7 it was packing 60 mph about 530 miles south of South Point, moving west at 9 mph. Between that peak and the Nov. 9 advisories it lost about 20 mph, which is the gap between the minimal hurricane the early forecasts described and the poorly organized system now being tracked.
Shear, dry air and the track toward the dateline
Mahoney wrote that Pena is no longer expected to strengthen. Increasing shear from the west-southwest and drier mid-level air could weaken it to a remnant low, and it remains possible that Pena dissipates within the next couple of days. The forecast still carries it as a tropical cyclone through the whole period, a convention that keeps the track and intensity string continuous rather than a prediction of survival.
A remnant low keeps some circulation and cloud but no longer meets the definition of a tropical cyclone, so a downgrade would end the advisory series without any dramatic event. The steering is simple for now. A ridge to the north pushes the storm west at about 10 knots, taking it from 11.5 degrees north, 161.4 degrees west toward 11.2 degrees north, 170.1 degrees west at 48 hours. After that the forecast turns it west-northwest and faster as a trough crosses the northwestern Pacific, ending near 14.6 degrees north, 173.3 degrees east at 120 hours, west of the dateline.
The 5 p.m. update and what it says about intensity
The next discussion, number 14, came out at 5 p.m. HST with forecaster Kelly describing Pena as poorly organized that afternoon. The intensity forecast holds 35 knots at every point out to 120 hours, and Kelly noted that short-term fluctuations in strength are likely and that the system could degenerate into a remnant low sooner than the forecast shows.
The accompanying public advisory places the center at 11.7 degrees north, 162.7 degrees west, moving west at 14 mph, with a minimum central pressure of 1004 millibars. Tropical-storm-force winds reach out up to 105 miles from the center, and the advisory lists no coastal watches or warnings and no hazards affecting land.
Hawaii effects and the El Niño season
For the islands, the storm’s main influence has been indirect. The Star-Advertiser’s report on the storm’s formation said Pena was helping to boost the trade winds, bringing breezy to strong conditions with near-gale gusts in channels, and that a moisture plume dropped 2 to 5 inches of rain on windward Big Island areas.
The storm is forming in a year when the Pacific is running warm. NOAA’s Climate Prediction Center, in its Oct. 8 ENSO discussion, reports an El Niño advisory with a Nino-3.4 anomaly of +2.1 degrees C. The Star-Advertiser’s Nov. 7 account quoted the National Weather Service as saying a high pressure ridge north of the state would stay locked in place for the foreseeable future, which is what keeps Pena on a westward path far south of the state.
What remains unsettled is the timing of its end. The 5 p.m. Nov. 9 discussion keeps Pena alive on paper through Nov. 14, while the forecaster’s own wording leaves room for it to fade much sooner, and the next advisories will show which reading holds. Either way the storm is expected to stay several hundred miles from the islands, with no coastal watches or warnings in effect, so the forecast question is about the storm’s own survival rather than any threat to land.
This article was produced with the assistance of AI and reviewed by Morning Overview editors prior to publication.
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