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Tropical Depression BONNIE Forecast Discussion Number 26
2016-06-03 04:37:39| National Hurricane Center (Atlantic)
Issued at 1100 PM EDT THU JUN 02 2016 000 WTNT42 KNHC 030237 TCDAT2 TROPICAL DEPRESSION BONNIE DISCUSSION NUMBER 26 NWS NATIONAL HURRICANE CENTER MIAMI FL AL022016 1100 PM EDT THU JUN 02 2016 The last observations from an Air Force Reserve Hurricane Hunter aircraft from several hours ago showed that Bonnie had changed little in intensity and remained just below tropical storm strength. Since that time, the cloud pattern of the tropical cyclone has not become better organized, and the center appears to be located on the southeast edge of the main area of deep convection. The current intensity is held at 30 kt, and this is in agreement with the latest Dvorak estimates from both TAFB and SAB. There is a short window of opportunity for Bonnie to strengthen a bit as it traverses the Gulf Stream and the vertical shear remains light during the next 12 to 24 hours. After that time, increasing shear and cooler waters should cause the system to weaken and degenerate into a remnant low. The official intensity forecast is the same as that from the previous advisory. This is close to the model consensus and somewhat below the DSHIPS and LGEM predictions. By 96 hours, the post-tropical cyclone is expected to become absorbed by an extratropical low over the north Atlantic. The initial motion is about 055/5. The track forecast reasoning remains basically unchanged from the previous couple of advisory packages. Bonnie should continue to be steered by the flow on the southern edge of the mid-latitude westerlies and gradually turn eastward with acceleration over the next few days. The official forecast track is very similar to the previous one and close to a consensus of the dynamical models, which themselves are in good agreement. FORECAST POSITIONS AND MAX WINDS INIT 03/0300Z 35.7N 74.3W 30 KT 35 MPH 12H 03/1200Z 36.0N 72.6W 35 KT 40 MPH 24H 04/0000Z 36.4N 70.1W 35 KT 40 MPH 36H 04/1200Z 36.4N 66.7W 30 KT 35 MPH...POST-TROP/REMNT LOW 48H 05/0000Z 36.2N 63.0W 30 KT 35 MPH...POST-TROP/REMNT LOW 72H 06/0000Z 35.0N 54.5W 25 KT 30 MPH...POST-TROP/REMNT LOW 96H 07/0000Z...DISSIPATED $$ Forecaster Pasch
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Tropical Depression BONNIE Forecast Discussion Number 25
2016-06-02 22:37:06| National Hurricane Center (Atlantic)
Issued at 500 PM EDT THU JUN 02 2016 000 WTNT42 KNHC 022036 TCDAT2 TROPICAL DEPRESSION BONNIE DISCUSSION NUMBER 25 NWS NATIONAL HURRICANE CENTER MIAMI FL AL022016 500 PM EDT THU JUN 02 2016 Coastal observations, Doppler radar data, and reports from an Air Force Reserve Hurricane Hunter aircraft indicate that Bonnie is a little stronger than on the previous advisory, and the Stepped Frequency Microwave Radiometer instrument on the aircraft has estimated surface winds as high as 39 kt. However, these estimates are uncertain due to rain contamination and bathemetry issues. Based on other data, the initial intensity is increased to a possibly conservative 30 kt. The initial motion estimate is 050/5. There is little change in the track forecast philosophy since the last advisory. Bonnie continues to move along the southern edge of the mid-latitude westerlies, and the cyclone should move generally east-northeastward to eastward with a gradual increase in forward speed during the next couple of days. The track forecast follows the various consensus models, which remain tightly clustered. The center of Bonnie will be moving over warm Gulf Stream waters for the next 12 hours or so while the vertical wind shear is light. Thus, the intensity forecast calls for modest strengthening during that time, bringing Bonnie back to a tropical storm. After that, increasing shear and sea surface temperatures below 24C should cause Bonnie to again degenerate to a remnant low, with the system weakening to a trough in the westerlies by 96 hours. FORECAST POSITIONS AND MAX WINDS INIT 02/2100Z 35.4N 74.8W 30 KT 35 MPH 12H 03/0600Z 35.8N 73.4W 35 KT 40 MPH 24H 03/1800Z 36.3N 70.8W 35 KT 40 MPH 36H 04/0600Z 36.5N 67.7W 30 KT 35 MPH...POST-TROP/REMNT LOW 48H 04/1800Z 36.5N 63.9W 30 KT 35 MPH...POST-TROP/REMNT LOW 72H 05/1800Z 36.0N 55.5W 25 KT 30 MPH...POST-TROP/REMNT LOW 96H 06/1800Z...DISSIPATED $$ Forecaster Beven
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Tropical Depression BONNIE Forecast Discussion Number 24
2016-06-02 16:35:05| National Hurricane Center (Atlantic)
Issued at 1100 AM EDT THU JUN 02 2016 000 WTNT42 KNHC 021434 TCDAT2 TROPICAL DEPRESSION BONNIE DISCUSSION NUMBER 24 NWS NATIONAL HURRICANE CENTER MIAMI FL AL022016 1100 AM EDT THU JUN 02 2016 Satellite imagery and coastal radar data indicate that the low pressure area that was formerly Bonnie has developed persistent organized convection near the center. Based on this, the system is again being designated as a tropical depression. The initial intensity of 25 kt and central pressure of 1009 mb are based on surface data near the center, along with a satellite intensity estimate of 25 kt from TAFB. The initial motion estimate is 055/5. Bonnie is moving along the southern edge of the mid-latitude westerlies, and the cyclone should move generally east-northeastward to eastward with a gradual increase in forward speed during the next couple of days. The track forecast follows that of the various consensus models, which are tightly clustered. The center of Bonnie will be moving over warm Gulf Stream waters for the next 12-24 hours while the vertical wind shear is light. Thus, the intensity forecast calls for modest strengthening during that time. After that, increasing shear and sea surface temperatures below 24C should cause Bonnie to again degenerate to a remnant low, with the system dissipating by 72 hours. FORECAST POSITIONS AND MAX WINDS INIT 02/1500Z 35.1N 75.1W 25 KT 30 MPH 12H 03/0000Z 35.3N 74.2W 30 KT 35 MPH 24H 03/1200Z 35.8N 72.2W 30 KT 35 MPH 36H 04/0000Z 36.1N 69.5W 25 KT 30 MPH...POST-TROP/REMNT LOW 48H 04/1200Z 36.1N 66.2W 25 KT 30 MPH...POST-TROP/REMNT LOW 72H 05/1200Z...DISSIPATED $$ Forecaster Beven
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Post-Tropical Cyclone BONNIE Forecast Discussion Number 12
2016-05-30 16:37:14| National Hurricane Center (Atlantic)
Issued at 1100 AM EDT MON MAY 30 2016 000 WTNT42 KNHC 301437 TCDAT2 POST-TROPICAL CYCLONE BONNIE DISCUSSION NUMBER 12 NWS NATIONAL HURRICANE CENTER MIAMI FL AL022016 1100 AM EDT MON MAY 30 2016 Bonnie has been gradually weakening during the past 24 hours. Deep convection associated the depression dissipated around 0300 UTC, and the central pressure has risen several millibars since this time yesterday. Surface observations over land also indicate winds no higher than 15 kt near Bonnie's center of circulation, however, winds to around 25 kt are noted over water in a band well removed to the east. Given the absence of deep convection for about 12 hours, Bonnie no longer meets the criteria to be classified as a tropical cyclone and is being designated as a post-tropical/remnant low at this time. Sporadic convection could re-develop in association with Bonnie during the next few days, especially over land during peak diurnal heating. However, re-development into a tropical cyclone is not anticipated. Global models show the remnant low of Bonnie transitioning into an extratropical cyclone along a frontal zone just after 72 hours. The initial motion is estimated to be 065/02, although visible satellite imagery indicates little motion during the last few hours. The track model guidance shows the post-tropical cyclone generally meandering slowly east-northeastward during the next day or so in a region of weak southwesterly steering flow. A shortwave trough entering the Midwest in 2 to 3 days should cause the post- tropical cyclone to move northeast and then east-northeastward into the western Atlantic with an increase in forward speed. The new NHC track forecast is shifted a bit to the left of the previous one and keeps Bonnie over land during the next 3 days. There continues to be the potential for Bonnie to generate heavy rainfall and some flooding over portions of the Carolinas during the next 2 to 3 days. Future information on Bonnie can be found in Public Advisories issued by the Weather Prediction Center beginning at 5 PM EDT, under AWIPS header TCPAT2, WMO header WTNT32 KWNH, and on the web at http://www.wpc.ncep.noaa.gov. FORECAST POSITIONS AND MAX WINDS INIT 30/1500Z 33.4N 79.8W 25 KT 30 MPH...POST-TROP/REMNT LOW 12H 31/0000Z 33.7N 79.2W 25 KT 30 MPH...POST-TROP/REMNT LOW 24H 31/1200Z 33.9N 78.7W 25 KT 30 MPH...POST-TROP/REMNT LOW 36H 01/0000Z 34.2N 78.2W 25 KT 30 MPH...POST-TROP/REMNT LOW 48H 01/1200Z 34.8N 77.7W 25 KT 30 MPH...POST-TROP/REMNT LOW 72H 02/1200Z 36.2N 76.6W 25 KT 30 MPH...POST-TROP/REMNT LOW 96H 03/1200Z 37.7N 73.3W 25 KT 30 MPH...POST-TROP/EXTRATROP 120H 04/1200Z 38.8N 69.6W 25 KT 30 MPH...POST-TROP/EXTRATROP $$ Forecaster Kimberlain
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Tropical Depression BONNIE Forecast Discussion Number 11
2016-05-30 10:58:14| National Hurricane Center (Atlantic)
Issued at 500 AM EDT MON MAY 30 2016 000 WTNT42 KNHC 300858 TCDAT2 TROPICAL DEPRESSION BONNIE DISCUSSION NUMBER 11 NWS NATIONAL HURRICANE CENTER MIAMI FL AL022016 500 AM EDT MON MAY 30 2016 Radar and surface observations indicate that Bonnie has moved eastward and is now located along the coastline just east of Charleston, South Carolina. A late-arriving RapidSCAT pass from 0029 UTC showed several 25-27 kt surface wind vectors in a rain-free area 50-80 nmi south-southwest of the center. Since that time, some modest shower activity has developed in that same region, which supports maintaining Bonnie as a 25-kt depression on this advisory. The initial motion estimate is 040/04 kt. Bonnie is expected to remain a vertically shallow low pressure system throughout the forecast period, and should be steered slowly northeastward to east-northeastward by an approaching 700-500 mb shortwave trough that is expected to capture the small cyclone within the next 12 hours or so based on recent trends in water vapor satellite imagery. By Wednesday, Bonnie's forward speed is expected to increase as the cyclone moves along the northern side of the Bermuda-Azores subtropical ridge. This steering pattern should take Bonnie and its remnants across the coastline of the Carolinas during the next 2-3 days, and then offshore into the western Atlantic Ocean by days 4 and 5. The NHC track forecast is similar to the previous advisory track, and remains close to the GFS-ECMWF model consensus. Bonnie has been convectively challenged for the past 12 hours. Only narrow bands of weak to moderate convection have persisted near the center over land during the past 6 hours, and limited convection been developing over adjacent Atlantic waters. Furthermore, the 0000 UTC Charleston, South Carolina upper-air sounding showed than Bonnie was barely holding on to warm-core, tropical cyclone status with only 1 deg C warmer temperatures than the surrounding environment indicated between 500-300 mb. Given the dry mid-level air that overlays the cyclone and continued moderate-to-strong southerly vertical wind shear for the next 48 hours or so, any significant re-strengthening appears unlikely while Bonnie remains over near the cool coastal shelf waters. The SHIPS and LGEM models re-strengthen Bonnie back to tropical storm status by 36 hours, but this seems unlikely given that the cyclone will be over 22-24 deg C sea-surface temperatures and in proximity to land. The official intensity forecast calls for Bonnie to maintain its current intensity of 25 kt throughout the forecast period and become a remnant low pressure system by 48 hours. However, the latter could occur sooner than the official forecast is indicating. The primary concern from Bonnie continues to be locally heavy rainfall. Rainfall amounts of 6 to 8 inches have already been reported in portions of eastern Georgia and southern South Carolina, and additional rainfall amounts of 2 to 4 inches will be possible. FORECAST POSITIONS AND MAX WINDS INIT 30/0900Z 33.0N 79.5W 25 KT 30 MPH 12H 30/1800Z 33.3N 79.0W 25 KT 30 MPH 24H 31/0600Z 33.5N 78.4W 25 KT 30 MPH 36H 31/1800Z 33.8N 77.8W 25 KT 30 MPH 48H 01/0600Z 34.4N 77.0W 25 KT 30 MPH...POST-TROP/REMNT LOW 72H 02/0600Z 35.7N 75.6W 25 KT 30 MPH...POST-TROP/REMNT LOW 96H 03/0600Z 37.3N 72.9W 25 KT 30 MPH...POST-TROP/REMNT LOW 120H 04/0600Z 38.7N 69.0W 25 KT 30 MPH...POST-TROP/REMNT LOW $$ Forecaster Stewart
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