Tropical Storm Pena Discussion Number 15

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Tropical Storm Pena Discussion Number 15 NWS Central Pacific Hurricane Center Honolulu HI CP042026 Issued by NWS National Hurricane Center Miami FL 1100 PM HST Mon Nov 09 2026 Satellite imagery indicates that the convective structure associated with Pena has changed little over the past several hours. Deep convection has remained mostly confined to the northeastern and eastern portions of the circulation, due to moderate south-southwesterly vertical wind shear. A recent scatterometer pass showed a somewhat elongated low-level circulation and a highly asymmetric wind field, with the strongest winds located in the northeastern quadrant. The latest subjective and objective intensity estimates remain in the 30 to 45 kt range. Given these estimates and the relatively steady satellite presentation, the initial intensity is held at 35 kt. The initial motion is westward, or 270/12 kt. This general motion is expected to continue during the next 48 h as a low- to mid-level ridge builds to the north, with the center of Pena forecast to pass several hundred n mi south of Johnston Atoll. Thereafter, a gradual turn toward the west-northwest is forecast as a weakness develops in the ridge in response to a shortwave trough moving across the northwestern Pacific. The latest NHC track forecast has been shifted southward from the previous prediction toward the latest HCCA and GDMI aids. Moderate south-southwesterly vertical wind shear and possibly some drier mid-level air continue to limit Pena's ability to strengthen. Although guidance indicates that the shear should decrease somewhat during the next 12 to 24 h, only a few intensity models support modest strengthening over the next few days. Sea surface temperatures near 29 C are expected to persist along the forecast track. However, increasingly dry mid-level air beginning around 60 h and strengthening southwesterly vertical wind shear toward the end of the period should inhibit intensification. Given these factors, little overall change in intensity is forecast, although some fluctuations in strength are certainly possible. Pena could still degenerate into a remnant low or open into a trough, particularly later in the forecast period. The latest NHC intensity forecast is unchanged from the previous prediction and lies near the middle of the guidance envelope. FORECAST POSITIONS AND MAX WINDS INIT 10/0900Z 11.7N 163.9W 35 KT 40 MPH 12H 10/1800Z 11.5N 165.6W 35 KT 40 MPH 24H 11/0600Z 11.2N 167.7W 35 KT 40 MPH 36H 11/1800Z 11.1N 170.2W 35 KT 40 MPH 48H 12/0600Z 11.3N 173.3W 35 KT 40 MPH 60H 12/1800Z 11.8N 176.3W 35 KT 40 MPH 72H 13/0600Z 12.3N 179.4W 35 KT 40 MPH 96H 14/0600Z 13.1N 175.2E 35 KT 40 MPH 120H 15/0600Z 13.5N 171.1E 35 KT 40 MPH