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Tropical Storm Kiko Forecast Discussion Number 31

2019-09-20 04:53:08| National Hurricane Center (East Pacific)

Issued at 800 PM PDT Thu Sep 19 2019 000 WTPZ43 KNHC 200253 TCDEP3 Tropical Storm Kiko Discussion Number 31 NWS National Hurricane Center Miami FL EP132019 800 PM PDT Thu Sep 19 2019 Kiko's structure hasn't change much since the previous advisory. The asymmetric pattern of the convection suggests that the cyclone is under the influence of some shear, which UW-CIMMS is analyzing to be about 20 kt from the southwest. The initial intensity is being maintained at 45 kt based on consensus Dvorak estimates of T3.0 from TAFB and SAB. A break in the mid-level steering ridge has allowed Kiko to turn northwestward, or 305/5 kt. For the next 5 days, the ridge is expected to restrengthen and then weaken again as a mid- to upper-level trough digs southward. As a result, Kiko is expected to take a sinuous track while moving generally westward, staying between 16N-18N. Even with that expectation, there is significant divergence in the models toward the end of the forecast period, with the GFS showing Kiko meandering and the ECMWF keeping the cyclone on a determined westward course. Because of this uncertainty, the updated NHC track has been slowed down a bit from the previous one. There has been a significant change in the intensity guidance, with most of the models showing Kiko's strength decreasing for much of the forecast period. Because there is so much uncertainty, the new NHC intensity forecast brings Kiko's winds to 50 kt in 12 hours, and then flatlines that intensity through day 4. Weakening is possible by the end of the forecast period due to a potential increase in shear. Even though the updated NHC forecast has been lowered from the previous one, it is still above the HCCA model and the multi-model consensus aids, and additional adjustment could be required in subsequent advisories. FORECAST POSITIONS AND MAX WINDS INIT 20/0300Z 16.6N 129.6W 45 KT 50 MPH 12H 20/1200Z 17.2N 130.1W 50 KT 60 MPH 24H 21/0000Z 17.7N 130.7W 50 KT 60 MPH 36H 21/1200Z 17.9N 131.4W 50 KT 60 MPH 48H 22/0000Z 17.6N 132.5W 50 KT 60 MPH 72H 23/0000Z 16.6N 134.6W 50 KT 60 MPH 96H 24/0000Z 17.0N 136.5W 50 KT 60 MPH 120H 25/0000Z 18.2N 137.5W 45 KT 50 MPH $$ Forecaster Berg

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Post-Tropical Cyclone Humberto Forecast Discussion Number 30

2019-09-20 04:49:08| National Hurricane Center (Atlantic)

Issued at 1100 PM AST Thu Sep 19 2019 000 WTNT44 KNHC 200249 TCDAT4 Post-Tropical Cyclone Humberto Discussion Number 30 NWS National Hurricane Center Miami FL AL092019 1100 PM AST Thu Sep 19 2019 Satellite images show what little deep convection remains has been displaced well to the north of the center of the cyclone, and it can no longer be classified via the Dvorak technique. Moreover, cold air stratocumulus clouds over the western and southern portions of the circulation are indicative of cold air advection that is characteristic of an extratropical cyclone. Therefore, Humberto is now post-tropical and this will be the last advisory issued by the National Hurricane Center on this system. It is estimated that the cyclone still has hurricane-force winds and based on continuity from previous estimates with a gradual weakening rate, the current intensity is set at 85 kt. Continued gradual weakening is likely, and after 48 hours the system is expected to merge with another extratropical low over the north Atlantic. The cyclone has turned north-northeastward along the eastern side of a deep layer cyclonic circulation, with a current motion estimate of 030/17 kt. A turn toward the east-northeast is expected in a day or so as the system moves within the mid-latitude westerlies until dissipation. Key Messages: 1. Large swells will continue to affect Bermuda, the northwestern Bahamas, and the east coast of the United States from east-central Florida to the Mid-Atlantic States during the next couple of days. These swells could create life-threatening surf and rip current conditions. FORECAST POSITIONS AND MAX WINDS INIT 20/0300Z 40.0N 58.0W 85 KT 100 MPH...POST-TROP/EXTRATROP 12H 20/1200Z 41.8N 56.8W 70 KT 80 MPH...POST-TROP/EXTRATROP 24H 21/0000Z 44.0N 54.0W 60 KT 70 MPH...POST-TROP/EXTRATROP 36H 21/1200Z 45.5N 48.0W 55 KT 65 MPH...POST-TROP/EXTRATROP 48H 22/0000Z 46.5N 40.5W 50 KT 60 MPH...POST-TROP/EXTRATROP 72H 23/0000Z...DISSIPATED $$ Forecaster Pasch

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Hurricane Jerry Forecast Discussion Number 11

2019-09-20 04:46:41| National Hurricane Center (Atlantic)

Issued at 1100 PM AST Thu Sep 19 2019 000 WTNT45 KNHC 200246 TCDAT5 Hurricane Jerry Discussion Number 11 NWS National Hurricane Center Miami FL AL102019 1100 PM AST Thu Sep 19 2019 The Air Force Hurricane Hunters investigating Jerry this evening found that the hurricane has strengthened. Based on the 700 mb flight-level winds from the aircraft, the current intensity is estimated to be about 90 kt. It should be noted that this is substantially higher than the intensity estimates provided from satellite data, and underscores the value of aerial reconnaissance of tropical cyclones. An expected increase in vertical shear in a day or so is expected to cause a weakening trend to commence in 12 to 24 hours, however, Jerry should remain a hurricane throughout the forecast period. This NHC intensity forecast is higher than the previous one mainly due to the higher initial wind speed, and is near or a little above the model consensus. Jerry remains on track and continues to move west-northwestward, or 295/14 kt. Over the next couple of days, the hurricane should continue this general motion with some slowing of forward speed as it moves along the southwestern periphery of a subtropical ridge. Thereafter, Jerry is likely to turn to the northwest, then north-northwest, and north as it moves through a weakness in the ridge. The track prediction models are in good agreement on this scenario, and the official forecast is quite close to the previous one. This is also very similar to the NOAA corrected consensus model, or HCCA, track. Key Messages: 1. Although the core of Jerry is expected to move north of the northern Leeward Islands, life-threatening flash floods are possible, along with tropical-storm-force winds in some areas. FORECAST POSITIONS AND MAX WINDS INIT 20/0300Z 18.0N 57.2W 90 KT 105 MPH 12H 20/1200Z 18.8N 59.3W 90 KT 105 MPH 24H 21/0000Z 20.0N 62.0W 85 KT 100 MPH 36H 21/1200Z 21.2N 64.5W 75 KT 85 MPH 48H 22/0000Z 22.6N 66.4W 70 KT 80 MPH 72H 23/0000Z 25.7N 68.4W 65 KT 75 MPH 96H 24/0000Z 29.0N 67.2W 65 KT 75 MPH 120H 25/0000Z 35.0N 63.0W 65 KT 75 MPH $$ Forecaster Pasch

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Tropical Storm Lorena Forecast Discussion Number 11

2019-09-20 04:41:11| National Hurricane Center (East Pacific)

Issued at 900 PM MDT Thu Sep 19 2019 000 WTPZ45 KNHC 200241 TCDEP5 Tropical Storm Lorena Discussion Number 11 NWS National Hurricane Center Miami FL EP152019 900 PM MDT Thu Sep 19 2019 Geostationary satellite data and a recently received SSM/IS overpass suggest that Lorena has gotten a little better organized since the last advisory, with a central dense overcast forming near or over a small mid-level eye seen in the microwave data. However, the various objective and subjective satellite intensity estimates indicate that the cyclone has not yet regained hurricane strength. The initial intensity is thus held at 60 kt. The initial motion is a somewhat uncertain 305/9. Lorena is located between a mid- to upper-level ridge over northern Mexico and Tropical Storm Mario to the south-southwest, while a large mid- to upper-level trough is northwest of Lorena over the western United States and the northeastern Pacific. The potential for Lorena to interact with Mario is producing a large spread in the guidance and a low confidence track forecast. Much of the track guidance, including the GFS, HWRF, HMON, and the GFS ensemble mean show Lorena turning so sharply westward around the north side of Mario that it passes south of the Baja California peninsula. At the other extreme is the older version of the GFS, which forecasts Lorena to moved northwestward up the Gulf of California due mainly to the influence of the Mexican ridge and the U. S. trough. The ECMWF model forecasts a track generally over the Baja California peninsula, while the UKMET shows a track into the southern Gulf of California followed by a westward turn across southern Baja. The new forecast track is similar to the previous track in forecasting Lorena to pass near the southern end of the Baja California peninsula, then move generally northwestward near the west coast of the peninsula. The new track lies well to the right of the various consensus models, but it lies to the left of the ECWMF and the old GFS model. Adjustments to the forecast track may occur once the amount of influence Mario will have on Lorena become more apparent. The intensity forecast is also very uncertain due to the track forecast uncertainties. The new intensity forecast is based on the track forecast that keeps Lorena over the water near the west coast of the the Baja California peninsula, with the cyclone re-gaining hurricane status before it moves over colder sea surface temperatures and eventually dissipates over the cold water. However there are three alternate scenarios. First, the GFS suggests the possibility that Mario will absorb Lorena and cause it to completely dissipate. Second, the older version of the GFS, with its forecast over the warm waters of the Gulf of California, would could allow Lorena to be stronger than currently forecast. Finally, the ECMWF's track over the Baja California Peninsula would also cause Lorena to weaken faster than currently forecast. The forecast track requires new warnings and watches for portions of Baja California del Sur. Additional warnings and watches may be required for this area on Friday. Key Messages: 1. Heavy rainfall will continue over portions of the Mexican states of Michoacan, Colima, and Jalisco during the next day or so. This rainfall may produce life-threatening flash flooding and mudslides. 2. Lorena is forecast to re-strengthen into a hurricane and bring hurricane-force winds and heavy rainfall to a portion of the southern Baja California peninsula beginning on Friday. A Hurricane Warning has been issued, and preparations to protect life and property should be rushed to completion. FORECAST POSITIONS AND MAX WINDS INIT 20/0300Z 22.3N 107.7W 60 KT 70 MPH 12H 20/1200Z 22.6N 108.8W 65 KT 75 MPH 24H 21/0000Z 23.1N 110.2W 70 KT 80 MPH 36H 21/1200Z 23.9N 111.4W 70 KT 80 MPH 48H 22/0000Z 24.8N 112.5W 60 KT 70 MPH 72H 23/0000Z 27.5N 114.8W 35 KT 40 MPH 96H 24/0000Z 29.5N 116.0W 25 KT 30 MPH...POST-TROP/REMNT LOW 120H 25/0000Z...DISSIPATED $$ Forecaster Beven

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Tropical Storm Mario Forecast Discussion Number 11

2019-09-20 04:31:37| National Hurricane Center (East Pacific)

Issued at 900 PM MDT Thu Sep 19 2019 000 WTPZ44 KNHC 200231 TCDEP4 Tropical Storm Mario Discussion Number 11 NWS National Hurricane Center Miami FL EP142019 900 PM MDT Thu Sep 19 2019 A new, solid burst of deep convection developed over Mario's center a little after 2200 UTC and has persisted since that time. As a result, Dvorak intensity estimates went back up to T3.5/55 kt from TAFB and SAB, and the latest UW-CIMSS SATCON estimate was 50-55 kt. As a result, Mario's initial intensity has been brought back up to 55 kt. Mario is essentially being pulled northeastward, or 045/8 kt, toward the circulation of Tropical Storm Lorena. That being said, all the major global models are now in agreement that Mario will not merge with Lorena, and a strengthening mid-level ridge over northern Mexico should force Mario to turn sharply northward and then northwestward during the next 2 days. This northwestward motion is likely to continue for the rest of the 5-day forecast period, with the cyclone's forward speed slowing down on days 4 and 5 as it moves into a weaker steering pattern. This forecast reasoning is not too different from the previous forecast, although the new NHC track has been nudged a bit to the left of the previous one to account for an overall shift in the guidance envelope. It should be noted that the deterministic ECMWF is an outlier and brings Mario to the Baja California peninsula as a weakening storm, but the bulk of that model's ensemble members favor the ocean-ward tracks shown by the other models. These ensemble solutions help to increase our confidence in the NHC track forecast. UW-CIMSS is analyzing about 5 kt of shear over Mario, and given the expanding convective canopy over the center, this could definitely be realistic. The shear could remain low enough for the next day or so to allow for some strengthening, which is shown by a number of the intensity models, and by extension, the NHC forecast. After 24 hours, increasing easterly shear is likely to lead to gradual weakening, with colder waters leading to a dissipation of all convection by day 4, if not sooner. The NHC forecast therefore now shows Mario degenerating into a remnant low on day 4. FORECAST POSITIONS AND MAX WINDS INIT 20/0300Z 17.6N 110.2W 55 KT 65 MPH 12H 20/1200Z 18.5N 109.8W 60 KT 70 MPH 24H 21/0000Z 19.6N 110.2W 60 KT 70 MPH 36H 21/1200Z 20.5N 111.5W 55 KT 65 MPH 48H 22/0000Z 21.3N 112.9W 50 KT 60 MPH 72H 23/0000Z 23.2N 115.9W 35 KT 40 MPH 96H 24/0000Z 24.7N 118.2W 30 KT 35 MPH...POST-TROP/REMNT LOW 120H 25/0000Z 24.4N 119.6W 25 KT 30 MPH...POST-TROP/REMNT LOW $$ Forecaster Berg

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