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Hurricane Paulette Forecast Discussion Number 27
2020-09-13 16:50:35| National Hurricane Center (Atlantic)
Issued at 1100 AM AST Sun Sep 13 2020 000 WTNT42 KNHC 131450 TCDAT2 Hurricane Paulette Discussion Number 27 NWS National Hurricane Center Miami FL AL172020 1100 AM AST Sun Sep 13 2020 An Air Force Hurricane Hunter aircraft investigating Paulette this morning found peak 700-mb flight-level winds of 92 kt, which reduces to around 75 kt at the surface. However, around that same time the peak winds measured by the SFMR instrument on board the aircraft were only 58 kt. It is possible that the stronger winds suggested by the flight-level values were not reaching the surface at that location. Later on in the flight, the SFMR measured 64-kt winds in the northwestern quadrant. Since there has been no notable change to the structure of the hurricane since the aircraft was in the system a few hours ago, the initial intensity is being held at 70 kt and is a compromise of those two different peak values measured by the aircraft. Infrared satellite imagery has been showing some dry air intrusion over the eastern portion of the circulation, causing a break in the eyewall there over the past few hours. There is currently deep convection firing around the remainder of the eyewall, and therefore it is anticipated the dry air will be worked out of the system soon. Very low wind shear and warm waters will support strengthening over the next couple of days, and Paulette is expected to be a dangerous hurricane as it nears Bermuda Monday morning. The window for strengthening should continue for another 12-24 h after the cyclone passes Bermuda, and Paulette could become a major hurricane during that time. After 48 h, vertical wind shear is forecast to rapidly increase. After 72 h, Paulette is expected to cross the 26 degree C SST isotherm, and by 120 h those SSTs will be near 22 degrees C. The NHC forecast shows a weakening trend beginning after 48 h due to the negative environmental factors. By 120 h, the global models suggest that Paulette will have completed a transition to an extratropical cyclone. The only change to the NHC intensity forecast from the previous advisory was a slight upward adjustment over the first few days due to the increase in strength found by the aircraft this morning. This forecast is in between the LGEM and HFIP corrected consensus, HCCA. Paulette is now moving northwestward at 12 kt, to the southwest of a mid-level ridge. This motion should continue until just after the cyclone passes Bermuda. Later on Monday, the hurricane should turn north, then on Monday night northeastward, as it rounds the periphery of the ridge. After turning northeastward, the cyclone is expected to accelerate as it gets picked up in the mid-latitude flow ahead of an approaching mid- to upper-level trough. Later on in the forecast period, a slower eastward motion is indicated once the aforementioned trough bypasses the cyclone. The latest NHC forecast track is little changed from the previous one through 48 h and lies in the middle of the latest global and regional track model guidance. Beyond 48 h, the NHC forecast is a little faster than the previous one, and lies near the tightly clustered consensus track guidance. On the forecast track, tropical storm conditions should reach Bermuda by this evening, with hurricane force winds arriving there overnight. Key Messages: 1. Paulette is expected to approach Bermuda as a hurricane today and will be near the island tonight and Monday. A prolonged period of strong winds, storm surge, and heavy rainfall is expected on Bermuda beginning this evening, and a hurricane warning is in effect for the island. Preparations to protect life and property should be rushed to completion. 2. Swells produced by Paulette are affecting portions of the Leeward Islands, the Greater Antilles, the Bahamas, Bermuda, and the east coast of the United States. These swells could cause life-threatening surf and rip current conditions. FORECAST POSITIONS AND MAX WINDS INIT 13/1500Z 29.9N 61.9W 70 KT 80 MPH 12H 14/0000Z 30.9N 63.6W 80 KT 90 MPH 24H 14/1200Z 32.8N 64.8W 90 KT 105 MPH 36H 15/0000Z 35.0N 63.5W 95 KT 110 MPH 48H 15/1200Z 37.0N 60.0W 100 KT 115 MPH 60H 16/0000Z 39.1N 55.1W 95 KT 110 MPH 72H 16/1200Z 41.4N 49.1W 85 KT 100 MPH 96H 17/1200Z 43.9N 42.0W 65 KT 75 MPH 120H 18/1200Z 44.0N 36.6W 50 KT 60 MPH...POST-TROP/EXTRATROP $$ Forecaster Latto
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