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Tropical Storm Lane Forecast Discussion Number 7
2018-08-16 16:56:12| National Hurricane Center (East Pacific)
Issued at 800 AM PDT Thu Aug 16 2018 858 WTPZ44 KNHC 161456 TCDEP4 Tropical Storm Lane Discussion Number 7 NWS National Hurricane Center Miami FL EP142018 800 AM PDT Thu Aug 16 2018 Lane appears to be intensifying this morning, with a more symmetric presentation on satellite imagery and pulsing deep convection near the center. A recent SSMI/S microwave pass indicates that an inner core is trying to form, although it isn't well defined yet. The current intensity estimates continue to display a large spread, ranging from the overnight scatterometer data at low-end tropical- storm strength, from hurricane strength in the TAFB Dvorak estimate. The initial wind speed is set to 50 kt with the increased organization, and this remains a low confidence estimate. While so far Lane has only been slowly intensifying, the large-scale environment appears favorable for more significant intensification to occur soon, especially with current signs of a primitive inner core. Thus the wind speed forecast will maintain the quick strengthening from the previous forecast, and there remains a significant chance that rapid intensification will occur during the next few days. The biggest change from yesterday is that more of the global models are indicating that westerly shear could affect Lane in the central Pacific, so more weakening is shown at day 5. Otherwise, the new NHC intensity forecast is very close to the previous one and is on the higher side of the guidance. The initial motion estimate is 275/11. The subtropical ridge to the north of Lane should continue to be the dominant steering mechanism, forcing the tropical cyclone to move westward or west-northwestward for the next several days. While the model spread is low in the short range, it notably increases by days 4/5. The GFS-based guidance is showing Lane move slower than the rest of the guidance, which allows the eastern periphery of the ridge to erode due to an inverted mid-level trough, and consequently a more poleward motion of the cyclone. The ECMWF and UKMET show Lane moving faster and basically missing any influence of that trough, causing the storm to move faster to the west. There are no strong signals pointing me to either solution, so the official forecast follows the trend of the consensus, which ends up slightly west of the previous forecast. FORECAST POSITIONS AND MAX WINDS INIT 16/1500Z 10.6N 127.6W 50 KT 60 MPH 12H 17/0000Z 10.8N 129.4W 60 KT 70 MPH 24H 17/1200Z 11.2N 132.1W 75 KT 85 MPH 36H 18/0000Z 11.7N 134.9W 85 KT 100 MPH 48H 18/1200Z 12.2N 137.6W 95 KT 110 MPH 72H 19/1200Z 13.5N 142.7W 105 KT 120 MPH 96H 20/1200Z 14.7N 147.3W 105 KT 120 MPH 120H 21/1200Z 15.3N 151.5W 95 KT 110 MPH $$ Forecaster Blake
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