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Tropical Storm Jose Forecast Discussion Number 5

2017-09-06 16:39:27| National Hurricane Center (Atlantic)

Issued at 1100 AM AST Wed Sep 06 2017 000 WTNT42 KNHC 061439 TCDAT2 Tropical Storm Jose Discussion Number 5 NWS National Hurricane Center Miami FL AL122017 Issued by the NWS Weather Prediction Center College Park MD 1100 AM AST Wed Sep 06 2017 Jose is better organized this morning with an initial Dvorak intensity estimate of T3.5 from TAFB. This estimate lies between a lower SAB T3.0 and CIMSS ADT T4.0. Since the initial Dvorak fix, SSMIS microwave imagery is showing a well defined center and an enhanced outer band, a precursor to potentially rapid intensification. Therefore initial intensity has been increased to 60 knots, slightly higher than TAFB T number. Initial position estimate is a compromise of TAFB and SAB satellite fixes and a steady west-northwest motion at 15 knots should continue on the southwest periphery of extensive subtropical ridge to the north and northeast of Jose. Satellite imagery does reveal drier air north of Jose but general trends suggest favorable upper level outflow and, given considerable distance, do any not expect any adverse influences from Irma to effect Jose at this time. Both satellite and model guidance indicate Jose will continue to exist within a very favorable synoptic regime to support intensification through 72 hours. Although the models agree on the overall scenario, there is support for somewhat stronger ridging north of Jose and official track has subsequently been shifted slightly left/west of previous forecast track but remains very close to model consensus. FORECAST POSITIONS AND MAX WINDS INIT 06/1500Z 13.1N 44.5W 60 KT 70 MPH 12H 07/0000Z 13.7N 46.7W 70 KT 80 MPH 24H 07/1200Z 14.3N 49.7W 80 KT 90 MPH 36H 08/0000Z 14.8N 52.6W 85 KT 100 MPH 48H 08/1200Z 15.4N 55.3W 90 KT 105 MPH 72H 09/1200Z 17.3N 58.9W 95 KT 110 MPH 96H 10/1200Z 20.2N 61.7W 90 KT 105 MPH 120H 11/1200Z 23.6N 64.9W 80 KT 90 MPH $$ Forecasters Carbin/Bann/Lamers

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Tropical Storm Katia Forecast Discussion Number 4

2017-09-06 16:33:16| National Hurricane Center (Atlantic)

Issued at 1000 AM CDT Wed Sep 06 2017 000 WTNT43 KNHC 061433 TCDAT3 Tropical Storm Katia Discussion Number 4 NWS National Hurricane Center Miami FL AL132017 1000 AM CDT Wed Sep 06 2017 Satellite and microwave data indicate that the cloud pattern associated with Katia is gradually becoming better organized with abundant convection near the center and improving outflow. An average of subjective numbers from TAFB and SAB as well as objective Dvorak T-numbers from CIMMS yield an initial intensity of 40 kt, or perhaps a little bit higher. An Air Force plane will check Katia later today, and we will have a better estimate of the structure of the cyclone. Currently, the upper-level wind pattern is not very conducive for strengthening, but most of the global models as well as the SHIPS guidance indicate that the environment will become favorable with weaker shear. On this basis, the NHC forecast calls for Katia to become a hurricane before it approaches the coast of the state of Veracruz. Katia is embedded within weak steering currents, and the cyclone will most likely meander in the southwestern Gulf of Mexico for the next day or two. After that time global models develop a ridge over the northern Gulf of Mexico and this flow pattern will steer Katia southwestward toward the state of Veracruz. The NHC forecast is basically on top of the multi-model consensus and is not very different from the previous NHC track. Given the upward intensity trend and the forecast track toward the coast, a hurricane watch could be required for a portion of the coast of the state of Veracruz later today. This system is forecast to bring very heavy rains primarily to the state of Veracruz during the next few days. FORECAST POSITIONS AND MAX WINDS INIT 06/1500Z 21.7N 95.9W 40 KT 45 MPH 12H 07/0000Z 21.4N 95.4W 50 KT 60 MPH 24H 07/1200Z 21.0N 95.0W 55 KT 65 MPH 36H 08/0000Z 21.0N 95.2W 60 KT 70 MPH 48H 08/1200Z 20.7N 95.4W 65 KT 75 MPH 72H 09/1200Z 19.5N 97.0W 25 KT 30 MPH...POST-TROP/INLAND 96H 10/1200Z...DISSIPATED $$ Forecaster Avila

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Hurricane Irma Forecast Discussion Number 29

2017-09-06 10:54:38| National Hurricane Center (Atlantic)

Issued at 500 AM AST Wed Sep 06 2017 000 WTNT41 KNHC 060854 TCDAT1 Hurricane Irma Discussion Number 29 NWS National Hurricane Center Miami FL AL112017 500 AM AST Wed Sep 06 2017 Irma continues as a Category 5 hurricane this morning, having passed over Barbuda a few hours ago. Earlier data from an Air Force Reserve Hurricane Hunter aircraft included SFMR winds near 155 kt and that the central pressure had fallen to 914 mb inside the 25 n mi wide eye. There has been little change in the satellite appearance of the hurricane since that time, so the initial intensity remains 160 kt. The initial motion is 285/14. Irma is currently being steered by the subtropical ridge to the north, and a general west- northwestward motion on the south side of the ridge is expected during the next 48-72 h. This portion of the forecast track is little changed and is in best overall agreement with the ECMWF model. The forecast has become more uncertain after 72 h due to large eastward shifts by the ECMWF, Canadian, and HWRF models related to forecasts of the mid- to upper-level trough over the southeastern United States. The bulk of the guidance now calls for Irma to turn northward between 78W-80W, moving near or over the Florida east coast or the northwestern Bahamas. The official forecast has also been shifted eastward, but out of respect for the previous forecast and the possibility the guidance may shift back to the west, it lies to the left of the bulk of the guidance. The forecast now calls for landfall in south Florida between 96-120 h. Users are reminded to not focus on the exact forecast track, especially at the longer ranges, since the average NHC track errors are about 175 and 225 statute miles at days 4 and 5, respectively. Irma is likely to remain in a light shear, warm water, environment for the next 3 to 4 days. The intensity guidance continues to show slow weakening during this time, and this part of the intensity forecast is little changed from the previous advisory, with Irma remaining a strong hurricane during this time. The intensity forecast is lowered at 120 h due to the forecast landfall, and even if Irma stays over water it is likely to encounter some vertical shear at that time. KEY MESSAGES: 1. Irma is a potentially catastrophic category 5 hurricane and will bring life-threatening wind, storm surge, and rainfall hazards to portions of the northern Leeward Islands, including the Virgin Islands and Puerto Rico, today. Preparations should be rushed to completion. 2. A Hurricane Warning is in effect for the northern coast of the Dominican Republic, as well as the southeastern Bahamas and the Turks and Caicos, with hurricane watches for portions of Haiti and the central Bahamas. Irma is likely to bring dangerous wind, storm surge, and rainfall to these areas from Wednesday night through Friday. 3. Irma could directly affect the remainder of the Bahamas and Cuba as an extremely dangerous major hurricane later this week. Residents in these areas should monitor the progress of Irma and listen to advice given by officials. 4. The chance of direct impacts from Irma beginning later this week and this weekend from wind, storm surge, and rainfall continues to increase in the Florida Keys and portions of the Florida Peninsula. However, it is too soon to specify the timing and magnitude of these impacts. FORECAST POSITIONS AND MAX WINDS INIT 06/0900Z 17.9N 62.6W 160 KT 185 MPH 12H 06/1800Z 18.6N 64.6W 155 KT 180 MPH 24H 07/0600Z 19.6N 67.3W 150 KT 175 MPH 36H 07/1800Z 20.6N 70.0W 145 KT 165 MPH 48H 08/0600Z 21.3N 72.5W 140 KT 160 MPH 72H 09/0600Z 22.5N 77.0W 135 KT 155 MPH 96H 10/0600Z 24.0N 80.0W 125 KT 145 MPH 120H 11/0600Z 26.5N 80.9W 105 KT 120 MPH...INLAND $$ Forecaster Beven

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Tropical Storm Katia Forecast Discussion Number 3

2017-09-06 10:44:42| National Hurricane Center (Atlantic)

Issued at 400 AM CDT Wed Sep 06 2017 000 WTNT43 KNHC 060844 TCDAT3 Tropical Storm Katia Discussion Number 3 NWS National Hurricane Center Miami FL AL132017 400 AM CDT Wed Sep 06 2017 Conventional satellite imagery shows improved organization of the cloud pattern during the past several hours, with recent cold cloud top of -80C associated with deep convective bursts near the surface center. An earlier SSMI/S microwave pass also revealed a developing curved band feature in the eastern portion of the cyclone. Additionally, a 0306 UTC ASCAT-B overpass indicated winds of 35 kt in the aforementioned rain band. A Dvorak satellite intensity estimate of 35 kt from TAFB and the scatterometer wind data support upgrading the depression to Tropical Storm Katia at this time. The SHIPS model and the CIMSS shear analysis indicate westerly shear impinging the western side of Katia, but the flow aloft appears to be more diffluent now, indicative of the recent deep convective outbreak. Guidance continues to suggest that the shear will relax in about 36 hours which should allow Katia to strengthen, possibly to a hurricane as indicated in the HWRF forecast. There are no changes to the intensity forecast from the previous advisory, and it's based on the IVCN multi-model. The initial motion is estimated to be east-southeastward, or 110/2 kt. Katia has been drifting generally in this direction during the past several hours within weak steering currents associated with a mid-tropospheric trough digging southwestward from the Mississippi Valley. Later today, Katia should begin a gradual turn southeastward and southwestward around the 36 hour period as a mid-level ridge builds over the western gulf from Texas. The official forecast basically splits the guidance envelope and is hedged toward the HFIP Corrected Consensus Model. FORECAST POSITIONS AND MAX WINDS INIT 06/0900Z 22.1N 96.3W 35 KT 40 MPH 12H 06/1800Z 21.9N 96.0W 40 KT 45 MPH 24H 07/0600Z 21.6N 95.6W 50 KT 60 MPH 36H 07/1800Z 21.3N 95.4W 55 KT 65 MPH 48H 08/0600Z 21.1N 95.6W 60 KT 70 MPH 72H 09/0600Z 20.4N 96.7W 60 KT 70 MPH 96H 10/0600Z 19.2N 98.7W 25 KT 30 MPH...POST-TROP/INLAND 120H 11/0600Z...DISSIPATED $$ Forecaster Roberts

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Tropical Storm Jose Forecast Discussion Number 4

2017-09-06 10:32:40| National Hurricane Center (Atlantic)

Issued at 500 AM AST Wed Sep 06 2017 000 WTNT42 KNHC 060832 TCDAT2 Tropical Storm Jose Discussion Number 4 NWS National Hurricane Center Miami FL AL122017 500 AM AST Wed Sep 06 2017 Satellite images indicate that Jose's banding features are becoming better established, and the center is now located near the middle of the central dense overcast. An average of the Dvorak estimates from TAFB/SAB and ADT values from CIMSS at the University of Wisconsin at 0600 UTC supported an intensity of 45 kt, but since the storm continues to organize, the initial wind speed is nudged upward to 50 kt at this time. Satellite fixes suggest that Jose is moving westward at 11 kt. A slightly faster westward to west-northwestward motion is expected during the next 2 to 3 days while Jose moves in the flow on the south and southwest sides of a subtropical high. After that time, a slower northwestward motion is forecast when Jose moves into a weakness in the ridge. Although the models agree on the overall scenario, there is a considerable amount of spread in the 4 to 5 day period on when and where Jose makes the northwest turn. The NHC official track forecast is shifted slightly to the left of the previous one to come into better agreement with the latest consensus aids. Additional steady strengthening seems likely during the next few days since Jose is expected to remain in favorable environmental conditions. In fact, the SHIPS model shows a 28 percent chance of Jose rapidly intensifying during the next 24 hours. Therefore, the NHC intensity forecast lies near the high end of the model guidance, bringing Jose to hurricane strength by tonight and to near major hurricane strength in 72 hours. Thereafter, an increase in vertical wind shear and drier air should end the strengthening trend and cause some weakening. This intensity forecast is largely an update of the previous one, and it is in good agreement with the HCCA model. FORECAST POSITIONS AND MAX WINDS INIT 06/0900Z 12.5N 42.8W 50 KT 60 MPH 12H 06/1800Z 13.0N 45.0W 60 KT 70 MPH 24H 07/0600Z 13.7N 48.0W 70 KT 80 MPH 36H 07/1800Z 14.3N 50.9W 80 KT 90 MPH 48H 08/0600Z 14.9N 53.7W 90 KT 105 MPH 72H 09/0600Z 16.7N 57.8W 95 KT 110 MPH 96H 10/0600Z 19.4N 60.5W 90 KT 105 MPH 120H 11/0600Z 22.7N 63.6W 80 KT 90 MPH $$ Forecaster Cangialosi

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