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Appendix C: What we Heard from the Discussion Draft

2019-09-16 22:37:40| PortlandOnline

PDF Document, 361kbCategory: DOZA Proposed Draft

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Hurricane Kiko Forecast Discussion Number 18

2019-09-16 22:35:59| National Hurricane Center (East Pacific)

Issued at 200 PM PDT Mon Sep 16 2019 000 WTPZ43 KNHC 162035 TCDEP3 Hurricane Kiko Discussion Number 18 NWS National Hurricane Center Miami FL EP132019 200 PM PDT Mon Sep 16 2019 There hasn't been a lot of change in Kiko during the day, with the cyclone keeping a small central core and no hints of an eye feature. While there is plenty of outflow, the sharp edge in the cirrus canopy on the north side is indicative of the maintenance of northeasterly shear. Intensity estimates are lower than this morning, and the initial wind speed is reduced to 85 kt. Weakening is anticipated during the next day or so as the shear continues. The forecast is more complicated after that time since the track keeps adjusting southward over warmer water while the shear relaxes. This change results in some models showing re-intensification in a few days, although that's temporary since the shear is forecast to resume at long range. To account for this scenario, the new forecast shows a small bump up in intensity for later this week, and we will just have to see how far south Kiko makes it before making a more significant increase in winds. Kiko continues to move westward at 4 kt to the south of a weak mid- level ridge. The hurricane is forecast to turn to the west- southwest by tomorrow due to a mid-level ridge building in from the central Pacific. This ridge is then forecast to weaken by 72 hours, while subtropical ridging builds to the north and northeast of the cyclone. This should result in a general westward to west- northwestward track through the end of the forecast period. The majority in the models are south of their previous tracks, starting the south-of-west motion as early as tonight. Thus the new forecast is adjusted south of the last NHC prediction, and this is not a particularly confident situation due to the unsteadiness of most of the guidance. FORECAST POSITIONS AND MAX WINDS INIT 16/2100Z 17.3N 124.1W 85 KT 100 MPH 12H 17/0600Z 17.1N 124.7W 75 KT 85 MPH 24H 17/1800Z 16.8N 125.5W 65 KT 75 MPH 36H 18/0600Z 16.6N 126.4W 55 KT 65 MPH 48H 18/1800Z 16.6N 127.5W 55 KT 65 MPH 72H 19/1800Z 17.0N 129.7W 60 KT 70 MPH 96H 20/1800Z 17.3N 130.7W 50 KT 60 MPH 120H 21/1800Z 17.3N 132.0W 40 KT 45 MPH $$ Forecaster Blake

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Hurricane Kiko Forecast Discussion Number 17

2019-09-16 16:51:26| National Hurricane Center (East Pacific)

Issued at 800 AM PDT Mon Sep 16 2019 000 WTPZ43 KNHC 161451 TCDEP3 Hurricane Kiko Discussion Number 17 NWS National Hurricane Center Miami FL EP132019 800 AM PDT Mon Sep 16 2019 Microwave data and satellite imagery continue to indicate that the core of Kiko is being disrupted. While there is a seemingly favorable outflow pattern, northeasterly shear is undercutting the top layer and preventing the cyclone from having a closed eyewall. Satellite estimates are falling and support a perhaps-generous initial wind speed of 90 kt. The shear is forecast to continue during the next day or so, which should promote further weakening. After that time, the shear could lessen, although the environment overall is hardly very conducive for strengthening, and this scenario would best support little change in intensity. By Friday-Saturday, model guidance does show an increase in shear, so a more notable weakening could occur. The new NHC intensity forecast is reduced from the previous one, following the trend in the guidance, but is a bit above the model consensus. A fair number of models actually show a weaker cyclone, but in a complex environment, I'd rather be conservative in changing the longer-range intensity forecast. There's no significant track change to report with Kiko. The hurricane is moving westward at 4 kt, to the south of a weak mid-level ridge. By 36 hours, another ridge building to the northwest of the hurricane will begin to steer Kiko to the west-southwest. This ridge is then forecast to weaken by 72 hours, while subtropical ridging builds to the north and northeast of the cyclone. This will likely result in a general westward to west-northwestward track through the end of the forecast period. The new forecast track is close to the previous one, on the faster and southern side of the guidance, which has generally been the right place to be with Kiko's track. FORECAST POSITIONS AND MAX WINDS INIT 16/1500Z 17.3N 123.7W 90 KT 105 MPH 12H 17/0000Z 17.3N 124.3W 80 KT 90 MPH 24H 17/1200Z 17.2N 125.1W 70 KT 80 MPH 36H 18/0000Z 16.9N 126.0W 65 KT 75 MPH 48H 18/1200Z 16.7N 127.0W 60 KT 70 MPH 72H 19/1200Z 16.9N 129.1W 60 KT 70 MPH 96H 20/1200Z 17.3N 130.7W 55 KT 65 MPH 120H 21/1200Z 17.3N 132.5W 45 KT 50 MPH $$ Forecaster Blake

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Hurricane Humberto Forecast Discussion Number 16

2019-09-16 16:50:58| National Hurricane Center (Atlantic)

Issued at 1100 AM EDT Mon Sep 16 2019 000 WTNT44 KNHC 161450 TCDAT4 Hurricane Humberto Discussion Number 16 NWS National Hurricane Center Miami FL AL092019 1100 AM EDT Mon Sep 16 2019 An Air Force Reserve reconnaissance aircraft investigating Humberto this morning found peak 850-mb flight-level winds of 88 kt in the southeastern and northeastern quadrants, along with SFMR surface winds of 72-73 kt in the northeastern quadrant and a minimum pressure of 978 mb. These data support an intensity of 75 kt. The initial motion estimate is east-northeastward or 070/06 kt. Humberto is now solidly located north of the Bermuda-Azores ridge axis, and a continued east-northeastward motion is expected for the 48 hours or so. Thereafter, a large deep-layer trough is forecast to dig southward out of Atlantic Canada and the Canadian Maritimes to the west of Humberto, forcing the hurricane to gradually lift out to the northeast. The exact timing that the trough begins to affect Humberto's motion will be critical in determining how close the hurricane will come to Bermuda. The latest model guidance is in better agreement and more tightly packed than previous runs, suggesting that the poleward turn will occur at least 100 n mi west of the island. By days 4 and 5, however, the model guidance becomes strongly divergent with a large spread of about 1000 n mi on day 5, resulting in lower-than-normal confidence in the track forecast on those days. The new NHC track foreast was nudged only slightly southward through 48 hours, and lies close to a blend of the consensus models TVCN, NOAA-HCCA, and FSSE. Humberto has been strengthening at a rate of 20 kt per 24 hours since this time yesterday, and that trend is expected to continue for the next day or so given the warm water beneath the hurricane and a continued favorable upper-level outflow pattern. The hurricane is expected to peak as a major hurricane in 36-48 hours when the cyclone will be located over SSTs of about 29 deg C and moving into the right-rear quadrant of a strong upper-level jet maximum. Thereafter, strong southwesterly vertical wind shear is expected to gradually diminish convection around the center despite the impressive baroclinic/dynamically driven pressure falls, which will mainly act to spread out the surface wind field rather than intensify the cyclone. Humberto is forecast to interact with an approaching cold front on day 5, resulting in extratropical transition over the colder Atlantic waters north of the Gulf Stream. The official intensity forecast is just an update of the previous advisory and now shows Humberto reaching major hurricane status, similar to the HCCA, FSSE, and HWRF models. Since Humberto's wind field is expected to expand significantly by day 2, a Tropical Storm Watch for Bermuda will likely be required on the 500 pm EDT advisory. Large swells from Humberto will affect portions of the northwestern Bahamas and southeastern United States coast during the next few days. These swells are expected to produce dangerous surf conditions and life-threatening rip currents. See products issued by your local weather office for additional information. FORECAST POSITIONS AND MAX WINDS INIT 16/1500Z 29.9N 76.5W 75 KT 85 MPH 12H 17/0000Z 30.1N 75.6W 85 KT 100 MPH 24H 17/1200Z 30.4N 74.4W 95 KT 110 MPH 36H 18/0000Z 30.7N 72.7W 100 KT 115 MPH 48H 18/1200Z 31.3N 70.5W 95 KT 110 MPH 72H 19/1200Z 33.7N 65.0W 85 KT 100 MPH 96H 20/1200Z 37.9N 60.9W 70 KT 80 MPH 120H 21/1200Z 40.8N 56.8W 60 KT 70 MPH...POST-TROP/EXTRATROP $$ Forecaster Stewart

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Hurricane Humberto Forecast Discussion Number 15

2019-09-16 10:47:23| National Hurricane Center (Atlantic)

Issued at 500 AM EDT Mon Sep 16 2019 000 WTNT44 KNHC 160847 TCDAT4 Hurricane Humberto Discussion Number 15 NWS National Hurricane Center Miami FL AL092019 500 AM EDT Mon Sep 16 2019 The satellite presentation of the hurricane has continued to improve overnight, with the center embedded within a fairly symmetric area of cold cloud tops. Although no eye is evident in conventional satellite imagery, a ragged eye could be seen in long-range NWS Doppler radar data from Melbourne, Florida early in the night. Satellite intensity estimates from TAFB, SAB, and UW/CIMSS all support an intensity of 75 kt, and that is used as the initial wind speed for this advisory. An Air Force Reserve Hurricane Hunter aircraft is scheduled to investigate Humberto this morning, and should provide a better assessment of the storm's strength. Humberto is likely to continue intensifying during the next day or so while it moves over the warm waters of the Gulf stream and the shear is not expected to be prohibitive. The updated NHC forecast depicts a faster rate of strengthening over the first 36 hours than before, and is at the upper end of the guidance through that time. By 48 hours, increasing westerly shear should slow the intensification process, but baroclinic forcing caused by a mid-latitude trough is likely to help the cyclone remain strong until it begins its extratropical transition later in the period. Humberto is moving northeastward or 050/3 kt. The hurricane is forecast to move slowly east-northeastward during the next 24 hours, around the northwestern portion of a subtropical ridge. After that time, Humberto should continue on an east-northeastward heading, but at a slightly faster forward speed as a broad trough becomes established over the western Atlantic. Later in the period, a strong shortwave trough is forecast to dig southward which should cause Humberto to lift northeastward. The track guidance is in good agreement through 72 hours, and the confidence in that portion of the forecast is quite high. After that time, the forecast confidence decreases quite a bit as the model spread becomes unusually large. This is the due to differs in how Humberto interacts with the aforementioned trough. The GFS and HWRF shows Humberto getting caught by the trough as it cuts-off over the western Atlantic, while the ECMWF and UKMET show a more progressive solution, and take Humberto northeastward over the north Atlantic ahead of the trough. Given the model spread of more than 1000 n mi at day 5, the NHC track foreast remains close to the multi-model consensus, but confidence in the 4- and 5-day forecast is rather low. Large swells from Humberto will affect portions of the northwestern Bahamas and southeastern United States coast during the next few days. These swells are expected to produce dangerous surf conditions and life-threatening rip currents. See products issued by your local weather office for additional information. FORECAST POSITIONS AND MAX WINDS INIT 16/0900Z 29.7N 77.3W 75 KT 85 MPH 12H 16/1800Z 30.0N 76.6W 85 KT 100 MPH 24H 17/0600Z 30.3N 75.4W 90 KT 105 MPH 36H 17/1800Z 30.6N 73.9W 95 KT 110 MPH 48H 18/0600Z 31.0N 72.0W 95 KT 110 MPH 72H 19/0600Z 33.0N 66.5W 95 KT 110 MPH 96H 20/0600Z 37.0N 62.0W 75 KT 85 MPH 120H 21/0600Z 40.0N 58.5W 55 KT 65 MPH...POST-TROP/EXTRATROP $$ Forecaster Brown

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