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Hurricane Hilary Forecast Discussion Number 21
2017-07-26 16:36:09| National Hurricane Center (East Pacific)
Issued at 900 AM MDT Wed Jul 26 2017 000 WTPZ44 KNHC 261435 TCDEP4 Hurricane Hilary Discussion Number 21 NWS National Hurricane Center Miami FL EP092017 900 AM MDT Wed Jul 26 2017 Satellite images indicate that Hilary remains a powerful hurricane. The central dense overcast has become more symmetric, although convection is still preferentially forming in the eastern eyewall. Any eye feature, however, is somewhat less distinct than a few hours ago, and the latest microwave passes are again showing an open eyewall on the west side. Intensity estimates range from 82 to 99 kt, so the initial wind speed will stay at 90 kt. There are still hints of northerly shear in cirrus cloud motions from the 1-min GOES-16 data, although the cyclone's cloud canopy looks less distorted than yesterday. This shear is forecast to persist for the next day or two while the hurricane moves over warm waters. After that time, while the shear could decrease, Hilary will be traversing marginally warm waters, with some increase in drier, more stable air in the environment. Most of the guidance is in good agreement on little change in the short-term, with a gradual decrease in wind speed through 3 days. Beyond then, much colder waters should cause a more rapid weakening, along with some interaction with Irwin. The new NHC forecast is basically an update of the previous one and lies close to IVCN, the variable intensity model consensus. It should be noted that the ECMWF is on its own by intensifying Hilary to a major hurricane in 2 to 3 days. The initial motion is 280/11. The track forecast is essentially unchanged for the next 48 h, while Hilary is expected to be steered by the mid-level subtropical ridge to the north. After that time, the ridge is forecast to become weaker to due to a mid- to upper-level trough dropping over the Baja California peninsula. Models are not in good agreement on how much the ridge weakens due to this trough, leading to a wide disparity of solutions at long range. There has been little change in the guidance suite since 6z, so the official forecast is close to the previous one. FORECAST POSITIONS AND MAX WINDS INIT 26/1500Z 16.4N 112.3W 90 KT 105 MPH 12H 27/0000Z 16.7N 113.9W 90 KT 105 MPH 24H 27/1200Z 17.1N 115.7W 90 KT 105 MPH 36H 28/0000Z 17.5N 117.4W 85 KT 100 MPH 48H 28/1200Z 18.1N 118.9W 80 KT 90 MPH 72H 29/1200Z 19.7N 121.9W 75 KT 85 MPH 96H 30/1200Z 21.4N 125.4W 55 KT 65 MPH 120H 31/1200Z 23.0N 129.0W 35 KT 40 MPH $$ Forecaster Blake
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