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Hurricane Hector Forecast Discussion Number 12

2018-08-03 16:47:32| National Hurricane Center (East Pacific)

Issued at 800 AM PDT Fri Aug 03 2018 753 WTPZ45 KNHC 031447 TCDEP5 Hurricane Hector Discussion Number 12 NWS National Hurricane Center Miami FL EP102018 800 AM PDT Fri Aug 03 2018 The satellite presentation of Hector has degraded over the past several hours, with only occasional hints of an eye in the latest imagery. More notably, an AMSR2 microwave pass at 0945Z shows a secondary eyewall structure beginning, with a ring of convection noted at about a 30 n mi radius. All these data indicate that Hector has weakened, so the initial wind speed is conservatively reduced to 80 kt, near or just above the latest Dvorak estimates. The current northeasterly shear is forecast to abate by the numerical models during the next 12 hours, which would normally lead to a restrengthening of Hector. However, the secondary eyewall formation throws a wrinkle into the forecast, since that process usually takes longer than that amount of time. As a compromise, gradual intensification is shown starting tomorrow, with a small uptick on Sunday as Hector reaches warmer waters in a light-shear environment. The HWRF and HMON still show Hector becoming a major hurricane, so it is too soon to abandon that forecast. The new forecast is a blend of the latest corrected-consensus guidance and the previous forecast, resulting in about a 10-kt reduction from the last NHC prediction. Slow weakening is shown at the end of the forecast due to cooler SSTs and potential entrainment of drier mid-level air. The initial motion remains 270/10 kt. A large subtropical ridge should steer the hurricane westward for the next couple of days, then a weakness in the ridge develops, which should cause a more west-northwestward track. The model guidance suite is a little slower than yesterday, about 1 or 2 kt overall. While that doesn't sound like much, over the course of a forecast that could change the final cyclone position by a few degrees, so it is meaningful. In this particular case, a slower solution turns Hector to the west-northwest earlier in the forecast, since the hurricane feels the developing weakness to the north-northeast sooner. The new NHC track forecast follows the trend of the model consensus and is adjusted slightly to the north. FORECAST POSITIONS AND MAX WINDS INIT 03/1500Z 14.1N 128.8W 80 KT 90 MPH 12H 04/0000Z 14.2N 130.4W 80 KT 90 MPH 24H 04/1200Z 14.2N 132.4W 85 KT 100 MPH 36H 05/0000Z 14.1N 134.5W 90 KT 105 MPH 48H 05/1200Z 14.2N 136.6W 100 KT 115 MPH 72H 06/1200Z 15.1N 141.4W 100 KT 115 MPH 96H 07/1200Z 16.3N 146.7W 90 KT 105 MPH 120H 08/1200Z 17.0N 152.0W 85 KT 100 MPH $$ Forecaster Blake

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Hurricane Hector Forecast Discussion Number 11

2018-08-03 10:51:29| National Hurricane Center (East Pacific)

Issued at 200 AM PDT Fri Aug 03 2018 092 WTPZ45 KNHC 030851 TCDEP5 Hurricane Hector Discussion Number 11 NWS National Hurricane Center Miami FL EP102018 200 AM PDT Fri Aug 03 2018 Although Hector appeared to be disrupted by moderate northeasterly shear earlier this evening, its satellite presentation is generally back on the upswing. A WindSat pass around 0213 UTC revealed that the tiny mid-level eye of the hurricane was still intact, and this feature has at times been apparent once again in longwave and shortwave IR imagery. The initial intensity has been set at 90 kt based on the Dvorak CI numbers from TAFB and SAB. Even though the shear no longer appears to be a significant inhibiting factor, marginal sea surface temperatures and mid-level humidity could still be limiting factors for the intensity of Hector. All of the intensity guidance indicates that little change in intensity will occur over the next 24-36 hours, so only gradual strengthening is forecast. By days 2 and 3, the hurricane will be moving over warmer waters once again, so some additional strengthening seems likely at that time. This scenario is supported by the dynamical intensity models, all of which depict Hector as a strong major hurricane. The statistical guidance notably shows gradual weakening during this period, so confidence in this part of the forecast is low. By 96 h, Hector is expected to move over cooler SSTs and into a drier environment, so steady weakening is forecast. The new NHC intensity forecast is similar to the previous advisory and still favors the dynamical model solutions. The initial motion is now 270/10 kt. No significant changes have been made to the track forecast. Hector is expected to be steered westward by a large subtropical ridge for the next few days. A turn toward the west-northwest is anticipated early next week as a large deep-layer trough over the northern Pacific weakens the ridge. There is still a large amount of spread in the global models regarding the forward speed of Hector as it begins to turn west-northwestward. Despite the large spread, the consensus has not changed much, so the new NHC track forecast lies practically on top of the previous forecast, and remains close to the consensus aids HCCA and FSSE. FORECAST POSITIONS AND MAX WINDS INIT 03/0900Z 14.0N 127.8W 90 KT 105 MPH 12H 03/1800Z 14.0N 129.4W 90 KT 105 MPH 24H 04/0600Z 14.0N 131.6W 95 KT 110 MPH 36H 04/1800Z 14.0N 133.7W 100 KT 115 MPH 48H 05/0600Z 13.9N 135.8W 105 KT 120 MPH 72H 06/0600Z 14.5N 140.1W 110 KT 125 MPH 96H 07/0600Z 15.5N 145.5W 100 KT 115 MPH 120H 08/0600Z 16.5N 150.5W 90 KT 105 MPH $$ Forecaster Zelinsky

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Hurricane Hector Forecast Discussion Number 10

2018-08-03 04:41:58| National Hurricane Center (East Pacific)

Issued at 800 PM PDT Thu Aug 02 2018 184 WTPZ45 KNHC 030241 TCDEP5 Hurricane Hector Discussion Number 10 NWS National Hurricane Center Miami FL EP102018 800 PM PDT Thu Aug 02 2018 Hector's rapid intensification has ended for the moment, with satellite imagery showing that the eye has become cloud filled since the last advisory. In addition, recent satellite microwave data indicate some erosion of the central convection on the north side of the center, possibly due to shear or a tongue of dry air working into the cyclone. The initial intensity is held at 95 kt in best agreement with the most recent CIMSS satellite consensus intensity estimate, but it is possible that this is a little generous. The initial motion is 270/11. A large subtropical ridge to the north of Hector should steer the cyclone westward for the next three days or so, and this part of the forecast track is an update of the previous track. Beyond that time, the large-scale models forecast a large deep-layer trough to develop over the northeastern Pacific, causing a weakness in the ridge to the north of Hector, and leading to the cyclone turning west-northwestward. There is some spread in the guidance during this time, with the GFS forecasting a weaker ridge and a more northward track than the ECMWF. Overall, the guidance envelope has again shifted northward from 72-120 h, and the new forecast track does likewise in best agreement with the HCCA corrected consensus and Florida State Superensemble models. The intensity forecast remains low confidence. While the shear near Hector should subside during the next 12-24 h, the forecast track takes the cyclone over slightly cooler sea surface temperatures during this time. This part of the new intensity forecast thus calls for little change in strength. From 24-72 h, the cyclone should move over warmer water in a light shear environment, which looks favorable for strengthening. However, there is sharp divergence in the guidance for this part of the forecast, with the SHIPS and LGEM models forecasting weakening while the dynamical HWRF, HMON, and COAMPS-TC models forecast intensification to a major hurricane. The NHC forecast sides with the dynamical models for this period, and it lies near the upper edge of the intensity guidance. After 72 h, Hector is expected to gradually weaken as it moves into a drier air mass. FORECAST POSITIONS AND MAX WINDS INIT 03/0300Z 14.1N 126.9W 95 KT 110 MPH 12H 03/1200Z 14.1N 128.6W 95 KT 110 MPH 24H 04/0000Z 14.1N 130.8W 95 KT 110 MPH 36H 04/1200Z 14.0N 132.9W 100 KT 115 MPH 48H 05/0000Z 13.9N 135.1W 105 KT 120 MPH 72H 06/0000Z 14.0N 139.5W 115 KT 130 MPH 96H 07/0000Z 15.0N 144.5W 105 KT 120 MPH 120H 08/0000Z 16.5N 149.5W 95 KT 110 MPH $$ Forecaster Beven

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Hurricane Hector Forecast Discussion Number 9

2018-08-02 22:41:58| National Hurricane Center (East Pacific)

Issued at 200 PM PDT Thu Aug 02 2018 142 WTPZ45 KNHC 022041 TCDEP5 Hurricane Hector Discussion Number 9 NWS National Hurricane Center Miami FL EP102018 200 PM PDT Thu Aug 02 2018 Hector is a small but powerful hurricane this afternoon. Visible GOES-15 data show that it has a 10 n mi wide eye, surrounded by a increasingly symmetric area of deep convection. The latest satellite estimates at 18 UTC were between 90 kt and 95 kt, and since the presentation has continued to improve during the past few hours, the initial wind speed is set to 95 kt. Hector has intensified an impressive 50 kt over the past 24 hours- remarkable since the environment did not seem particularly favorable even 12 hours ago. What is perplexing about this forecast is that, despite all of the global models showing a more conducive environment during the next day or two, none of the regional hurricane models show intensification, and in fact they all show weakening. This would be a dramatic change, which seems pretty unlikely given the current state of things. It makes the most sense to show continuing strengthening, albeit at a reduced rate since the SSTs do moderate, in line with the SHIPS & LGEM models. The new forecast has a peak intensity at 72 hours when SSTs are the warmest with the lowest environmental shear. After that time, water temperatures and mid-level humidites should gradually decrease, which will probably promote some weakening. Obviously this is a low confidence forecast, and I wouldn't be surprised if it had to be raised in the short term later tonight. Hector continues on course, moving westward at 12 kt. The track forecast for the next 3 days is of high confidence, since the guidance is in good agreement and a large subtropical ridge is providing a well-defined steering current. Complications arise in the long range due to the potential interaction of Hector with a mid-level trough in the Central Pacific. The latest models show Hector moving into a weakness in the ridge associated with the trough, causing a more west-northwestward motion earlier in the forecast. This is a fairly subtle change but has led to most of the guidance trending to the north. The official forecast is shifted in that direction, but remains on the southwest side of the guidance envelope, close to the corrected-consensus models. FORECAST POSITIONS AND MAX WINDS INIT 02/2100Z 14.1N 125.8W 95 KT 110 MPH 12H 03/0600Z 14.0N 127.6W 100 KT 115 MPH 24H 03/1800Z 13.9N 129.8W 105 KT 120 MPH 36H 04/0600Z 13.9N 132.0W 105 KT 120 MPH 48H 04/1800Z 13.8N 134.3W 105 KT 120 MPH 72H 05/1800Z 13.6N 139.0W 115 KT 130 MPH 96H 06/1800Z 14.5N 144.0W 110 KT 125 MPH 120H 07/1800Z 15.5N 149.0W 105 KT 120 MPH $$ Forecaster Blake

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Hurricane Hector Forecast Discussion Number 8

2018-08-02 16:27:25| National Hurricane Center (East Pacific)

Issued at 800 AM PDT Thu Aug 02 2018 175 WTPZ45 KNHC 021427 TCDEP5 Hurricane Hector Discussion Number 8 NWS National Hurricane Center Miami FL EP102018 800 AM PDT Thu Aug 02 2018 Well, so much for the shear. Satellite images indicate that Hector is rapidly intensifying and has recently formed a small eye. The initial wind speed is set to 75 kt, based on the TAFB Dvorak estimate. While there still could be some shear over the next day or so, it seems apparent now that the highest shear should stay north of the tropical cyclone, leaving Hector in a pocket of lighter winds. The main inhibiting factor is expected to be more marginal SSTs, with temperatures below 27C in the path of the hurricane. The official forecast assumes the current intensification trend will last for another 12 hours or so, then levels off due to the more marginal waters, similar to the latest SHIPS/LGEM forecasts. It is worth noting that the regional hurricane models show an unrealistic solution of significant weakening in the short term, and have been disregarded. In the longer range, the upper-level environment and water temperatures are more than sufficient to support a major hurricane, and the new forecast reflects these conditions. Hector has turned westward and accelerated, now moving 12 kt. A large subtropical ridge is forecast to build westward over the next several days, keeping the cyclone on this general course into the Central Pacific. The ridge could weaken somewhat by day 5, causing a more west-northwestward motion early next week. Little change was made to the previous official track forecast, although it is a shade faster at the end of the period. FORECAST POSITIONS AND MAX WINDS INIT 02/1500Z 14.2N 124.6W 75 KT 85 MPH 12H 03/0000Z 14.3N 126.5W 90 KT 105 MPH 24H 03/1200Z 14.3N 128.7W 95 KT 110 MPH 36H 04/0000Z 14.2N 131.0W 95 KT 110 MPH 48H 04/1200Z 14.0N 133.3W 95 KT 110 MPH 72H 05/1200Z 13.6N 138.1W 100 KT 115 MPH 96H 06/1200Z 13.8N 143.1W 105 KT 120 MPH 120H 07/1200Z 14.5N 148.0W 105 KT 120 MPH $$ Forecaster Blake

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