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Tropical Storm Juliette Forecast Discussion Number 5
2019-09-02 10:40:42| National Hurricane Center (East Pacific)
Issued at 300 AM MDT Mon Sep 02 2019 000 WTPZ41 KNHC 020840 TCDEP1 Tropical Storm Juliette Discussion Number 5 NWS National Hurricane Center Miami FL EP112019 300 AM MDT Mon Sep 02 2019 After struggling to strengthen during the previous 12-h period due to the entrainment of mid-level dry air, a strong burst of deep convection, accompanied by frequent lightning and cloud tops near -90C, has developed near the well-defined low-level circulation center. A nearly circular CDO feature has also formed over the center, and the upper-level outflow has improved and expanded in all quadrants. During the past few hours, SSMI/S and AMSU microwave satellite data indicate that a primitive mid-level eye feature had formed, and recent satellite intensity estimates from TAFB and UW-CIMSS SATCON were T3.5/55 kt and 57 kt, respectively. Based on these data, the initial intensity has been increased to 55 kt. The initial motion is estimate is 300/12 kt. There is no significant change to the previous forecast track or rationale. A deep-layer ridge anchored to the north of Juliette is expected to change little, driving Juliette on a general west-northwestward track throughout the 5-day period. As a result, the new NHC track forecast is very similar to the previous advisory track, and lies down the middle of the tightly clustered model guidance. Now that a nearly complete mid-level eye feature has formed, rapid intensification is expected to occur during the next 24 hours due to Juliette being embedded within very favorable environmental conditions consisting of low vertical wind shear near 5 kt, an unhindered outflow pattern, and a moist mid-level environment, along with traversing warm sea-surface temperatures (SST) of 28-29 deg C. Thereafter, a slower rate of strengthening is expected through 36-48 hours due to the cyclone moving over marginal SSTs. Steady weakening is forecast on days 3-5 when Juliette will be moving over sub-26C SSTs despite low shear conditions. The new official intensity forecast is a little above all of the available intensity guidance, and shows the same peak intensity as the previous advisory, except that the time of occurrence has been moved forward by 24 hours. FORECAST POSITIONS AND MAX WINDS INIT 02/0900Z 16.2N 111.8W 55 KT 65 MPH 12H 02/1800Z 17.0N 113.2W 70 KT 80 MPH 24H 03/0600Z 17.9N 114.9W 85 KT 100 MPH 36H 03/1800Z 18.5N 116.4W 90 KT 105 MPH 48H 04/0600Z 19.0N 117.7W 90 KT 105 MPH 72H 05/0600Z 20.0N 121.3W 75 KT 85 MPH 96H 06/0600Z 21.5N 125.2W 60 KT 70 MPH 120H 07/0600Z 23.0N 129.5W 45 KT 50 MPH $$ Forecaster Stewart
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Hurricane Dorian Forecast Discussion Number 35
2019-09-02 04:59:30| National Hurricane Center (Atlantic)
Issued at 1100 PM EDT Sun Sep 01 2019 000 WTNT45 KNHC 020259 TCDAT5 Hurricane Dorian Discussion Number 35 NWS National Hurricane Center Miami FL AL052019 1100 PM EDT Sun Sep 01 2019 Dorian remains an incredibly powerful hurricane and it is currently making landfall on the eastern end of Grand Bahama Island. Satellite images show an symmetrical cyclone with a circular 10 n mi diameter eye and intense eyewall convection with lots of lightning being detected. Doppler radar data from Miami and the Bahamas show that Dorian has developed concentric eyewalls, and this feature is also noted by a double wind maximum that is evident in data from the Air Force Hurricane Hunters. The initial intensity of Dorian is set at 155 kt based mostly on the SFMR winds from the aircraft. The aircraft data also indicated that the radii of tropical-storm-force winds are a little larger than they were earlier today. Dorian is still moving slowly westward at about 5 kt. The ridge to the north of Dorian is gradually weakening and shifting eastward in response to a mid- to upper-level trough that is moving across the eastern U.S. This change in the steering pattern should cause Dorian to slow down even more and perhaps stall, before it turns to the northwest late Monday or early Tuesday. This expected slow motion will likely be devastating to the Great Abaco and Grand Bahama Islands since it would prolong the catastrophic winds, storm surge, and rainfall over those areas. The timing of the northwest or north turn is very critical in determining how close Dorian will get to the Florida peninsula on Tuesday and Wednesday. In general, the track models have changed little from the previous cycle, and the NHC forecast continues to show the core of Dorian very near, but offshore, of the Florida peninsula on Tuesday and Wednesday. The hurricane is then expected to track near the Georgia and Carolina coasts late this week. This forecast is in best agreement with the various consensus models, which typically have the lowest errors. It is once again emphasized that although the official track forecast does not show landfall, users should not focus on the exact track. A small deviation to the left of the track could bring the intense core of the hurricane and its dangerous winds closer to or onto the Florida coast. Category 5 hurricanes like Dorian usually don't hold that intensity for very long, and it is expected that Dorian will weaken slowly during the next few days. However, the observed eyewall replacement cycle will likely cause fluctuations in strength, both up and down, while the system is near Florida. The models show an increase in shear when Dorian tracks near Georgia and the Carolinas, which should cause more notable weakening. This forecast is near the high end of the latest model guidance. Based on this forecast, the hurricane watch has been extended northward to the Florida-Georgia line. Key Messages: 1. A prolonged period of catastrophic winds and storm surge will affect the Abaco Islands and Grand Bahama Island for several more hours. Everyone there should take immediate shelter and not venture into the eye. 2. Life-threatening storm surges and dangerous hurricane-force winds are expected along portions of the Florida east coast through mid-week, and storm surge and hurricane warnings are in effect. Only a slight deviation to the left of the official forecast would bring the core of Dorian near or over the Florida east coast. Residents should listen to advice given by local emergency officials. 3. There is an increasing likelihood of strong winds and dangerous storm surge along the coasts of Georgia, South Carolina, and North Carolina later this week. Residents in these areas should continue to monitor the progress of Dorian and listen to advice given by local emergency officials. 4. Heavy rains, capable of producing life-threatening flash floods, are expected over northern portions of the Bahamas and coastal sections of the southeast and lower mid-Atlantic regions of the United States through late this week. FORECAST POSITIONS AND MAX WINDS INIT 02/0300Z 26.6N 77.9W 155 KT 180 MPH 12H 02/1200Z 26.8N 78.5W 145 KT 165 MPH 24H 03/0000Z 26.9N 79.0W 135 KT 155 MPH 36H 03/1200Z 27.3N 79.3W 125 KT 145 MPH 48H 04/0000Z 28.2N 79.8W 120 KT 140 MPH 72H 05/0000Z 30.6N 80.2W 105 KT 120 MPH 96H 06/0000Z 33.5N 77.7W 85 KT 100 MPH 120H 07/0000Z 37.5N 71.8W 75 KT 85 MPH $$ Forecaster Cangialosi
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Tropical Storm Juliette Forecast Discussion Number 4
2019-09-02 04:41:58| National Hurricane Center (East Pacific)
Issued at 900 PM MDT Sun Sep 01 2019 000 WTPZ41 KNHC 020241 TCDEP1 Tropical Storm Juliette Discussion Number 4 NWS National Hurricane Center Miami FL EP112019 900 PM MDT Sun Sep 01 2019 Although there has been some new deep bursts of convection near the center of circulation this evening, the banding features still remain quite fragmented. The subjective Dvorak intensity estimates, as well as a recent UW-CIMSS SATCON analysis, support holding the initial intensity at 50 kt for this advisory. Juliette is expected to intensify at a near climatological rate during the next 48 hours, indicative of low deep-layer shear, a moist mid-level atmosphere, and warm oceanic sea surface temperatures. After 72 hours, Juliette will be moving over decreasing SSTs, and into a high statically stable marine layer air mass which should induce gradual weakening. The NHC forecast follows suit and is based on a blend of the NOAA HFIP HCCA and the IVCN multi-model intensity guidance. The initial motion is estimated to be west-northwestward, or 300/11 kt within the east-southeasterly steering flow produced by a mid-tropospheric ridge extending over the northeastern Pacific from the southwestern United States. The cyclone should continue moving west-northwestward through the forecast period with some reduction in forward speed during the next 48 hours. Beyond that time, the cross-track spread of the model guidance increases in response to large-scale synoptic differences in the strength of the subtropical ridge. The ECMWF and the Canadian still indicate the cyclone turning westward due to strengthening of the subtropical ridge, while the GFS, HWRF, and the UKMET reflect less ridging, and induce a more northwestward track. The new official forecast is nudged south of the previous forecast and lies between the TVCE consensus and the ECMWF global. FORECAST POSITIONS AND MAX WINDS INIT 02/0300Z 15.4N 110.6W 50 KT 60 MPH 12H 02/1200Z 16.3N 112.1W 60 KT 70 MPH 24H 03/0000Z 17.4N 114.1W 70 KT 80 MPH 36H 03/1200Z 18.1N 115.7W 85 KT 100 MPH 48H 04/0000Z 18.6N 117.1W 90 KT 105 MPH 72H 05/0000Z 19.5N 120.1W 80 KT 90 MPH 96H 06/0000Z 20.8N 124.0W 65 KT 75 MPH 120H 07/0000Z 22.4N 128.2W 50 KT 60 MPH $$ Forecaster Roberts
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Hurricane Dorian Forecast Discussion Number 34
2019-09-01 22:56:59| National Hurricane Center (Atlantic)
Issued at 500 PM EDT Sun Sep 01 2019 000 WTNT45 KNHC 012056 TCDAT5 Hurricane Dorian Discussion Number 34 NWS National Hurricane Center Miami FL AL052019 500 PM EDT Sun Sep 01 2019 The distinct eye of powerful Hurricane Dorian is moving over Great Abaco. The latest wind and pressure data from an Air Force reconnaissance plane just before the eye hit the island indicated that the winds reached 160 kt, which is the initial intensity for this advisory. It is not very often that we measure such strong winds. The minimum pressure measured by the plane was 910 mb. The eye has been shrinking, and an eyewall replacement cycle is possibly occurring. The effect of the island terrain and the eyewall replacement cycle should result in some slight fluctuations in intensity during the next 24 to 36 hours, but the hurricane will continue to be extremely dangerous one during that time. After 3 days, a more definite weakening trend should begin as the hurricane encounters stronger shear. Dorian however, it is forecast to remain a hurricane for the next 5 days. Dorian has slowed down even more and is now moving toward the west or 270 degrees at 4 kt. The steering currents are collapsing and Dorian is expected to slow down a little more, prolonging its catastrophic effects in the northwestern Bahamas. The NHC forecast calls for a slow west to west-northwest motion during the next 48 hours. A turn to the north and northeast with a gradual increase in forward speed is expected thereafter, as the mid-level trough over the eastern United States deepens. The current forecast is not very different from the previous one, and it is very close to the multi-model consensus TVCA. Both the deterministic and consensus tracks have shown the usual variability to the right or to the left from run to run, but the overall trend is for the hurricane to turn northward offshore but dangerously close to the Florida peninsula. Given the uncertainty in the track forecast and the anticipated increase in size of the hurricane, a Hurricane Warning and Storm Surge Warning have been issued for a portion of the Florida east coast. It is once again emphasized that although the official track forecast does not show landfall, users should not focus on the exact track. A small deviation to the left of the track could bring the intense core of the hurricane its dangerous winds closer to or onto the Florida coast. Key Messages: 1. A prolonged period of catastrophic winds and storm surge will affect the Abaco Islands and Grand Bahama Island tonight. Everyone there should take immediate shelter and not venture into the eye. 2. Life-threatening storm surge and dangerous hurricane-force winds are expected along portions of the Florida east coast through mid-week, and storm surge and hurricane warnings are in effect. Only a slight deviation to the left of the official forecast would bring the core of Dorian near or over the Florida east coast. Residents should listen to advice given by local emergency officials. 3. There is an increasing likelihood of strong winds and dangerous storm surge along the coasts of Georgia, South Carolina, North Carolina later this week. Residents in these areas should continue to monitor the progress of Dorian and listen to advice given by local emergency officials. 4. Heavy rains, capable of producing life-threatening flash floods, are expected over northern portions of the Bahamas and coastal sections of the southeast and lower mid-Atlantic regions of the United States through late this week. FORECAST POSITIONS AND MAX WINDS INIT 01/2100Z 26.6N 77.3W 160 KT 185 MPH 12H 02/0600Z 26.7N 78.1W 155 KT 180 MPH 24H 02/1800Z 26.8N 78.7W 145 KT 165 MPH 36H 03/0600Z 27.0N 79.0W 135 KT 155 MPH 48H 03/1800Z 27.7N 79.5W 125 KT 145 MPH 72H 04/1800Z 30.0N 80.3W 105 KT 120 MPH 96H 05/1800Z 33.0N 78.5W 90 KT 105 MPH 120H 06/1800Z 36.5N 73.5W 80 KT 90 MPH $$ Forecaster Avila
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Tropical Storm Juliette Forecast Discussion Number 3
2019-09-01 22:41:06| National Hurricane Center (East Pacific)
Issued at 300 PM MDT Sun Sep 01 2019 000 WTPZ41 KNHC 012041 TCDEP1 Tropical Storm Juliette Discussion Number 3 NWS National Hurricane Center Miami FL EP112019 300 PM MDT Sun Sep 01 2019 Juliette's presentation in visible satellite imagery has continued to improve, with hints of a banding eye now present. That said, the convection in the cyclone's bands is not that deep, and recent ASCAT data still supports an intensity of 50 kt. No change was made to the track forecast. The hurricane is moving northwest at 11 kt, steered primarily by a mid-level ridge centered over the southwestern US. All of the guidance shows that Juliette will move west-northwestward to northwestward for the next 3 days, with a slight decrease in forward speed. After that, differences in the forecasted strength of the ridge result in a larger model spread. The ECMWF shows Juliette turning nearly westward due to an amplification of the ridge, while the GFS forecasts that the ridge will weaken, causing Juliette to move farther north. The NHC forecast is nearly directly between those two models and lies very close to the model consensus at all forecast hours, but its worth noting that confidence in the track forecast is fairly low at 96 h and beyond. Low wind shear, a warm underlying ocean, and sufficient environmental moisture should allow Juliette to strengthen for the next 2-3 days. The largest uncertainty is the rate at which the tropical storm will strengthen, and the rapid intensification guidance is not quite as bullish as it was 6 hours ago. Subsequently, no major change was made to the intensity forecast, and Juliette is still expected to become a hurricane on Monday. By the end of the forecast, the cyclone will likely begin moving over cooler waters and through a far more stable environment. This should cause Juliette to weaken, particularly if it moves farther north than the NHC official forecast, as shown by the GFS. If Juliette takes a farther south track, like that of the ECMWF, it could maintain its intensity longer than currently forecast. FORECAST POSITIONS AND MAX WINDS INIT 01/2100Z 14.9N 109.7W 50 KT 60 MPH 12H 02/0600Z 15.9N 111.2W 60 KT 70 MPH 24H 02/1800Z 17.0N 113.1W 70 KT 80 MPH 36H 03/0600Z 17.9N 114.8W 85 KT 100 MPH 48H 03/1800Z 18.5N 116.3W 90 KT 105 MPH 72H 04/1800Z 19.5N 119.0W 85 KT 100 MPH 96H 05/1800Z 21.0N 122.5W 70 KT 80 MPH 120H 06/1800Z 23.0N 127.0W 50 KT 60 MPH $$ Forecaster Zelinsky
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