ZCZC HFOTCDCP2 ALL TTAA00 PHFO DDHHMM Hurricane Lane Discussion Number 29 NWS Central Pacific Hurricane Center Honolulu HI EP142018 500 PM HST Tue Aug 21 2018 Lane remains a powerful hurricane this afternoon, with a well- developed warm eye completely surrounded by persistent cold cloud tops. The Hurricane Hunter aircraft from the 53rd Weather Reconnaissance Squadron has been flying through Lane during the day, and has provided invaluable data. The central pressure dropped around 10 mb between the 18Z and 00Z fixes, with the last eye dropsonde measuring 930 mb with 16 kt splash wind, yielding a minimum pressure estimate of 929 mb. Peak SFMR winds during this mission were 140 kt, and max flight level winds were 146 kt. Subjective Dvorak current intensity estimates range from 6.5/127 kt to 7.0/140 kt, with the latest ADT current intensity holding steady at 6.5/127 kt. Although the central pressure has dropped sharply during the last 18 hours, it is now about what one would expect for a hurricane of strong Category 4 intensity in the Central Pacific basin, and based primarily on the aircraft data the intial intensity is held at 135 kt for this advisory. Lane has turned slightly to the WNW today, and the initial motion for this advisory is 285/8 kt. Lane has been moving generally westward to the south of a mid-level ridge during the past several days. However, this will be changing soon, as Lane begins to round the western periphery of this ridge and moves into an area of relatively light steering flow. This is expected to allow the cyclone to gain latitude as its forward speed diminishes. The hurricane is forecast to continue moving west-northwest tonight, then turn to the northwest on Wednesday, and to the north-northwest on Thursday, as it moves between the mid-level ridge to the east and a developing upper-level trough to the northwest of Hawaii. After this point, the track and intensity forecast become increasingly uncertain, as the majority of the reliable model guidance brings Lane very close to the islands with potential interaction between Lane and the mountainous terrain of the islands. This interaction combined with increasing vertical wind shear leads to a weakened Lane being steered to the west by the low-level trade wind flow during the later forecast periods. The new track forecast has been nudged slightly to left through 36 hours, then slightly to the right or closer to the islands at 72 hours, in very good agreement with the multi-model consensus HCCA. Water temperatures along the forecast track will be sufficiently warm to support a major hurricane, and thus any significant weakening before Lane draws closer to the Hawaiian Islands will likely be due to increasing wind shear. Through the next 36 to 48 hours, shear is expected to remain light, and we expect only slow weakening as the cyclone moves over slightly cooler SSTs and may be impacted by eyewall replacement cycles. At 72 hours and beyond, the forecast anticipates a sharp increase in shear as Lane moves closer to the large upper trough to the northwest of the main Hawaiian Islands. The new intensity forecast is very similar to the previous forecast, and continues to follow the trend of the multi-model consensus IVCN. In addition to continued storm penetrations by the Hurricane Hunters of the 53rd Weather Reconnaissance Squadron, the NOAA P-3 aircraft will also be flying into Lane again this evening. The NOAA G-IV aircraft once again sampled the larger scale environment during the day to help with initialization of the forecast models. KEY MESSAGES: 1. Lane is forecast to move dangerously close to the main Hawaiian Islands as a hurricane later this week, potentially bringing damaging winds and life-threatening flash flooding from heavy rainfall anywhere in the state. As Lane is expected to be slow-moving as it nears the islands, it will produce large and damaging surf. 2. As Lane moves up from the southeast, the earliest potential threat to land will be for the Big Island, where a Hurricane Warning is now in effect. Preparations there should be rushed to completion as tropical-storm force winds are forecast to arrive in the warning area by late Wednesday or early Thursday. A Hurricane Watch remains in effect for Maui County, and is now posted for Oahu, with tropical-storm force winds possibly beginning Thursday or Thursday night. 3. Due to a continued high degree of uncertainty on the forecast track and intensity of Lane, hurricane impacts could be felt across any of the Hawaiian Islands. It is too early to predict which, if any, of the islands are directly impacted. Remember that life threatening weather conditions can extend well away from the center of the hurricane. Interests throughout Hawaii are urged to closely monitor the progress of Lane during the next few days. FORECAST POSITIONS AND MAX WINDS INIT 22/0300Z 14.5N 154.0W 135 KT 155 MPH 12H 22/1200Z 15.0N 155.0W 130 KT 150 MPH 24H 23/0000Z 16.0N 156.0W 125 KT 145 MPH 36H 23/1200Z 17.2N 156.8W 115 KT 130 MPH 48H 24/0000Z 18.6N 157.3W 100 KT 115 MPH 72H 25/0000Z 21.1N 158.7W 75 KT 85 MPH 96H 26/0000Z 21.5N 161.5W 50 KT 60 MPH 120H 27/0000Z 21.0N 164.5W 40 KT 45 MPH $$ Forecaster Jacobson NNNN