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Hurricane ARTHUR Forecast Discussion Number 17

2014-07-05 04:37:31| National Hurricane Center (Atlantic)

Issued at 1100 PM EDT FRI JUL 04 2014 000 WTNT41 KNHC 050237 TCDAT1 HURRICANE ARTHUR DISCUSSION NUMBER 17 NWS NATIONAL HURRICANE CENTER MIAMI FL AL012014 1100 PM EDT FRI JUL 04 2014 Satellite and radar data indicates that Arthur has begun extratropical transition. The eye feature seen previously has dissipated, and the remaining convection is now displaced somewhat to the northeast of the low-level center. In addition, microwave total precipitable water data from a recent SSM/IS overpass shows very dry air entraining into the west and south sides of the cyclone. SFMR data from the previous Air Force Reserve Hurricane Hunter flight showed maximum winds of 60-65 kt, and based on this the initial intensity is reduced to a possibly generous 65 kt. The initial motion is now 045/27 kt. Arthur should continue to move northeastward during the next 24-36 hours in deep-layer southwesterly flow ahead of a baroclinic trough over the northeastern United States. After that time, the post-tropical cyclone is forecast to slow down and eventually turn east-northeastward. Based on the current motion and model trends, this part of the forecast has been nudged a little to the east of the previous track. There remains a large amount of spread in the track guidance after 48 hours on whether the former Arthur will turn more northward or turn east-northeastward out into the Atlantic. The new official forecast during that period has been revised based on a blend of input from the Ocean Prediction Center along with the GFS and ECMWF models. Arthur is expected to complete extratropical transition in about 12 hours. After transition, the former tropical cyclone should steadily weaken, with winds dropping below gale force by 96 hours. The intensity forecast has been revised downward based on input from the OPC, as well as from the GFS and ECMWF models. Winds in excess of gale/tropical storm force are expected over portions of eastern Maine on Saturday. Because Arthur is expected to be extratropical by Saturday morning, and because the strong winds in Maine will be post-frontal, this threat is being handled by high wind warnings issued by local NWS offices. FORECAST POSITIONS AND MAX WINDS INIT 05/0300Z 41.2N 68.7W 65 KT 75 MPH 12H 05/1200Z 44.0N 66.0W 60 KT 70 MPH...POST-TROP/EXTRATROP 24H 06/0000Z 46.5N 63.0W 50 KT 60 MPH...POST-TROP/EXTRATROP 36H 06/1200Z 48.5N 59.3W 40 KT 45 MPH...POST-TROP/EXTRATROP 48H 07/0000Z 51.5N 55.0W 35 KT 40 MPH...POST-TROP/EXTRATROP 72H 08/0000Z 58.0N 51.0W 35 KT 40 MPH...POST-TROP/EXTRATROP 96H 09/0000Z 60.0N 49.0W 30 KT 35 MPH...POST-TROP/EXTRATROP 120H 10/0000Z 61.5N 44.5W 25 KT 30 MPH...POST-TROP/EXTRATROP $$ Forecaster Beven

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Tropical Storm DOUGLAS Forecast Discussion Number 26

2014-07-05 04:36:01| National Hurricane Center (East Pacific)

Issued at 800 PM PDT FRI JUL 04 2014 000 WTPZ44 KNHC 050235 TCDEP4 TROPICAL STORM DOUGLAS DISCUSSION NUMBER 26 NWS NATIONAL HURRICANE CENTER MIAMI FL EP042014 800 PM PDT FRI JUL 04 2014 Douglas is hanging on as a tropical storm. After being devoid of deep convection for much of the day, a small area has redeveloped to the northeast of the center. The initial wind speed is held at 35 kt based on earlier scatterometer data and a Dvorak pattern T-number of 2.5 from TAFB. Douglas is currently over cold 23C waters and in a stable airmass. These hostile conditions should cause weakening, and the cyclone is forecast to become a remnant low by 24 hours. This is delayed slightly from the previous forecast. The storm is moving northwestward at about 6 kt. A low- to mid-level ridge to the northeast of Douglas should keep the system on a steady northwestward path until it dissipates in a few days. The track forecast is nudged to the north of the previous one, and is very near the multi-model consensus TVCE. FORECAST POSITIONS AND MAX WINDS INIT 05/0300Z 22.4N 119.1W 35 KT 40 MPH 12H 05/1200Z 23.1N 120.0W 30 KT 35 MPH 24H 06/0000Z 24.1N 121.3W 25 KT 30 MPH...POST-TROP/REMNT LOW 36H 06/1200Z 25.0N 122.5W 20 KT 25 MPH...POST-TROP/REMNT LOW 48H 07/0000Z 25.8N 123.5W 20 KT 25 MPH...POST-TROP/REMNT LOW 72H 08/0000Z...DISSIPATED $$ Forecaster Cangialosi

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Hurricane ARTHUR Forecast Discussion Number 15

2014-07-04 16:42:27| National Hurricane Center (Atlantic)

Issued at 1100 AM EDT FRI JUL 04 2014 000 WTNT41 KNHC 041442 TCDAT1 HURRICANE ARTHUR DISCUSSION NUMBER 15 NWS NATIONAL HURRICANE CENTER MIAMI FL AL012014 1100 AM EDT FRI JUL 04 2014 The eye of Arthur remains evident in geostationary satellite imagery although the cloud tops surrounding the eye have warmed this morning. The U.S. Air Force Reserve Hurricane Hunter aircraft has measured 94-kt 700 mb flight-level winds in the southeastern quadrant, but it appears that these winds are not effectively mixing down to the surface, as peak SFMR surface winds have been 68 kt. Using a blend of the these data, the initial intensity has been reduced to 80 kt. Arthur will be moving over cooler water and the shear will be significantly increasing through tonight, which should cause gradual weakening. The hurricane will also interact with a deep-layer trough and associated cold front that will be moving off the United States east coast later today. This should cause the hurricane to complete transition into an extratropical cyclone in about 24 hours. After that time, continued weakening is expected while the post-tropical cyclone moves over the North Atlantic. Arthur is moving northeastward with an initial motion of 040/21 kt. The hurricane should continue moving northeastward during the next 24 to 36 hours ahead of the aforementioned deep-layer trough. The center of the cyclone is forecast to move over Nova Scotia on Saturday and track models are in good agreement on this portion of the forecast. The track guidance become very divergent after 48 hours, with the ECMWF taking the cyclone northward and northwestward while the GFS shows an east-northeastward motion near Newfoundland. Out of continuity for the previous forecasts, the NHC track continues to follow the eastward scenario shown by the GFS and GFS ensemble mean, but it now shows a somewhat slower motion by day 5. It is possible that this portion of the track will need to be adjusted in future forecasts. Hourly position updates and two-hourly intermediate advisories have been discontinued. Three-hourly intermediate advisories will continue as long as coastal warnings remain in effect. FORECAST POSITIONS AND MAX WINDS INIT 04/1500Z 37.7N 73.4W 80 KT 90 MPH 12H 05/0000Z 40.2N 70.1W 75 KT 85 MPH 24H 05/1200Z 44.0N 66.1W 60 KT 70 MPH...POST-TROP/EXTRATROP 36H 06/0000Z 46.1N 63.2W 55 KT 65 MPH...POST-TROP/EXTRATROP 48H 06/1200Z 48.0N 59.0W 45 KT 50 MPH...POST-TROP/EXTRATROP 72H 07/1200Z 55.0N 52.0W 35 KT 40 MPH...POST-TROP/EXTRATROP 96H 08/1200Z 59.0N 46.0W 30 KT 35 MPH...POST-TROP/EXTRATROP 120H 09/1200Z 62.0N 35.0W 30 KT 35 MPH...POST-TROP/EXTRATROP $$ Forecaster Brown

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Hurricane ARTHUR Forecast Discussion Number 14

2014-07-04 11:01:25| National Hurricane Center (Atlantic)

Issued at 500 AM EDT FRI JUL 04 2014 000 WTNT41 KNHC 040901 TCDAT1 HURRICANE ARTHUR DISCUSSION NUMBER 14 NWS NATIONAL HURRICANE CENTER MIAMI FL AL012014 500 AM EDT FRI JUL 04 2014 Arthur still has a well-defined eye in radar imagery, and the cloud pattern features an area of cold cloud tops wrapping around the northern and western portions of the circulation as some dry air works its way into the southern semicircle. Before the Air Force Hurricane Hunters left Arthur, they measured flight-level winds of 91 kt and SFMR winds of 82 kt, which support maintaining the initial intensity at 85 kt. The central pressure is set to 973 mb based on a measurement of 975.5 mb at an NOAA National Ocean Service station at Oregon Inlet with a wind of 35 kt. Another Hurricane Hunter aircraft will be sampling Arthur later this morning. Gradual weakening is expected today and tonight, and Arthur will complete extratropical transition by 36 hours. After passing Nova Scotia, post-tropical Arthur should weaken rapidly over the North Atlantic. Arthur is accelerating northeastward, with an initial motion estimate of 040/20, and a northeastward motion is expected to continue for the next 48 hours as Arthur recurves ahead of an advancing mid-latitude trough. The track model guidance is in good agreement in taking the center of Arthur well offshore of the U.S. mid-Atlantic coast today and southeast of New England tonight before moving over Nova Scotia in about 36 hours. After that time, Arthur is expected to continue across Newfoundland and into the North Atlantic. The NHC track forecast is near the center of the guidance envelope through 72 hours and is close to the GEFS ensemble mean at days 4 and 5. The new experimental potential storm surge flooding map is available at: http://www.nhc.noaa.gov/graphics_at1.shtml?inundation FORECAST POSITIONS AND MAX WINDS INIT 04/0900Z 36.0N 75.3W 85 KT 100 MPH 12H 04/1800Z 38.4N 72.3W 80 KT 90 MPH 24H 05/0600Z 42.2N 68.0W 75 KT 85 MPH 36H 05/1800Z 45.5N 64.6W 65 KT 75 MPH...POST-TROP/EXTRATROP 48H 06/0600Z 47.5N 61.0W 55 KT 65 MPH...POST-TROP/EXTRATROP 72H 07/0600Z 53.5N 53.0W 35 KT 40 MPH...POST-TROP/EXTRATROP 96H 08/0600Z 59.0N 43.5W 30 KT 35 MPH...POST-TROP/EXTRATROP 120H 09/0600Z 63.0N 35.0W 30 KT 35 MPH...POST-TROP/EXTRATROP $$ Forecaster Brennan

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Hurricane ARTHUR Forecast Discussion Number 13

2014-07-04 05:01:53| National Hurricane Center (Atlantic)

Issued at 1100 PM EDT THU JUL 03 2014 000 WTNT41 KNHC 040301 TCDAT1 HURRICANE ARTHUR DISCUSSION NUMBER 13 NWS NATIONAL HURRICANE CENTER MIAMI FL AL012014 1100 PM EDT THU JUL 03 2014 The eye of Arthur is about to make landfall near Cape Lookout, North Carolina. An Air Force Reserve Hurricane Hunter aircraft reported 700-mb flight-level winds of 94 kt and SFMR winds of 79 kt in the southeastern eyewall. The lowest reported central pressure was 976 mb. Based on these data, the initial intensity was increased to 85 kt. Coastal radar data indicates a well-defined 20-25 n mi diameter eye is present, and the eye is also apparent in infrared satellite imagery. Arthur is accelerating toward the northeast due to the approach of a baroclinic trough over the northeastern United states, and the initial motion is now 035/16. A continued northeastward motion and acceleration are expected during the next 24-36 hours. The forecast track calls for the center to cross coastal North Carolina during the next several hours, pass southeast of New England in about 24 hours, and be near or over western Nova Scotia in about 36 hours. After that, the westerlies are expected to steer Arthur or its remnants across Newfoundland into the North Atlantic. The forecast track is similar to the previous track and lies near the center of the guidance envelope for the first 72 hours. Little change in strength is expected during the next 12 hours as the eye of the hurricane crosses coastal North Carolina and the adjacent northwestern Atlantic. After that, Arthur is expected to undergo extratropical transition, which is forecast to be complete by the time the cyclone reaches Nova Scotia. After passing Nova Scotia, a post-tropical Arthur should weaken rapidly over the North Atlantic. The new experimental potential storm surge flooding map is available at: http://www.nhc.noaa.gov/graphics_at1.shtml?inundation FORECAST POSITIONS AND MAX WINDS INIT 04/0300Z 34.6N 76.6W 85 KT 100 MPH 12H 04/1200Z 36.7N 74.5W 85 KT 100 MPH 24H 05/0000Z 40.0N 70.3W 80 KT 90 MPH 36H 05/1200Z 43.7N 66.1W 70 KT 80 MPH...POST-TROP/EXTRATROP 48H 06/0000Z 46.2N 62.6W 60 KT 70 MPH...POST-TROP/EXTRATROP 72H 07/0000Z 51.5N 54.0W 40 KT 45 MPH...POST-TROP/EXTRATROP 96H 08/0000Z 57.5N 44.5W 30 KT 35 MPH...POST-TROP/EXTRATROP 120H 09/0000Z 60.0N 35.0W 30 KT 35 MPH...POST-TROP/EXTRATROP $$ Forecaster Beven

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