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Tropical Depression Omar Forecast Discussion Number 14
2020-09-04 04:32:54| National Hurricane Center (Atlantic)
Issued at 1100 PM AST Thu Sep 03 2020 000 WTNT45 KNHC 040232 TCDAT5 Tropical Depression Omar Discussion Number 14 NWS National Hurricane Center Miami FL AL152020 1100 PM AST Thu Sep 03 2020 The larger mass of deep convection from earlier today that was south of the exposed low-level center of Omar has since dissipated. The only convection that remains is a few small patches in the eastern semicircle. The initial intensity is being lowered to 25 kt, and is based off a recent ASCAT overpass showing peak 26 kt wind vectors. If the current state of the tropical depression persists through much of tonight, then by definition the system would no longer qualify as a tropical cyclone. The only chance for Omar to hang on despite very strong northerly wind shear is the fact that it is still over SSTs of about 27 C. After 24 h, dry air is expected to envelop the system. Therefore, over this weekend whatever remains of Omar is expected to dissipate ahead of an approaching mid-latitude frontal system. The official NHC forecast shows Omar degenerating into a remnant low by Friday morning and dissipating by Sunday morning, and this scenario is in agreement with the global models. The depression continues to move east-southeast at 9 kt in steering flow around a subtropical ridge to its south, and another, larger low pressure system to its northeast. The other low is forecast to continue to lift northeastward, which should result in an end to the southerly component of Omar's motion tonight or early Friday. By Friday night, a turn to the northeast is expected to occur as Omar gets caught in southwesterly flow ahead of the approaching frontal system. The latest NHC track forecast is little changed from the previous one, and lies near the various consensus aids. FORECAST POSITIONS AND MAX WINDS INIT 04/0300Z 35.2N 59.1W 25 KT 30 MPH 12H 04/1200Z 35.2N 58.0W 25 KT 30 MPH...POST-TROP/REMNT LOW 24H 05/0000Z 35.6N 57.2W 25 KT 30 MPH...POST-TROP/REMNT LOW 36H 05/1200Z 36.8N 56.5W 25 KT 30 MPH...POST-TROP/REMNT LOW 48H 06/0000Z 38.3N 55.6W 25 KT 30 MPH...POST-TROP/REMNT LOW 60H 06/1200Z...DISSIPATED $$ Forecaster Latto
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Tropical Depression Nana Forecast Discussion Number 11
2020-09-03 22:36:20| National Hurricane Center (Atlantic)
Issued at 400 PM CDT Thu Sep 03 2020 000 WTNT41 KNHC 032036 TCDAT1 Tropical Depression Nana Discussion Number 11 NWS National Hurricane Center Miami FL AL162020 400 PM CDT Thu Sep 03 2020 Satellite imagery indicates that Nana continues to weaken over land, with only a small area of convection remaining near and to the south of the low-level center. It is estimated that Nana has weakened to a 30-kt tropical depression, although as with the last advisory there are no observations near the cyclone's core and thus the estimate is rather uncertain. Continued weakening is expected, and Nana is likely to be a remnant low pressure area by the time it reaches the Gulf of Tehuantepec in 12-24 h. The global models continue to forecast conditions that are not conducive for Nana to re-intensify, so the intensity forecast calls for the remnant low to dissipate by 48 h even though it will be over water. There is a possibility that a low pressure area will re-form over the Pacific in association with the remnants of Nana late this weekend or early next week, but the chances of re-generation to a tropical cyclone appear low at this time. The initial motion is 255/12 kt. A low- to mid-level ridge to the north of Nana should keep it moving on a westward to west-southwestward track during the remainder of the cyclone's life. The new official forecast track is again similar to the previous track and lies near the various consensus models, KEY MESSAGES: 1. Heavy rainfall with isolated maximum amounts as high as 3 to 6 inches could result in flash flooding in Guatemala and portions of southeastern Mexico. FORECAST POSITIONS AND MAX WINDS INIT 03/2100Z 16.0N 91.1W 30 KT 35 MPH...INLAND 12H 04/0600Z 15.5N 92.8W 25 KT 30 MPH...INLAND 24H 04/1800Z 15.0N 95.0W 20 KT 25 MPH...POST-TROP/REMNT LOW 36H 05/0600Z 14.7N 97.3W 20 KT 25 MPH...POST-TROP/REMNT LOW 48H 05/1800Z...DISSIPATED $$ Forecaster Beven
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Tropical Depression Omar Forecast Discussion Number 13
2020-09-03 22:34:53| National Hurricane Center (Atlantic)
Issued at 500 PM AST Thu Sep 03 2020 000 WTNT45 KNHC 032034 TCDAT5 Tropical Depression Omar Discussion Number 13 NWS National Hurricane Center Miami FL AL152020 500 PM AST Thu Sep 03 2020 The GOES-16 visible and enhanced infrared satellite presentation has changed little during the past several hours and is comprised of a sheared depression with a deep convective mass decoupled well to the south of the surface circulation center. Based on the earlier METOP-B scatterometer pass and the Dvorak satellite intensity estimates, the initial intensity remains at 30 kt. Gradual weakening is still forecast during the next couple of days as the cyclone continues to move in the persistent, blistering northerly shear environment on the order of 40 to 45 kt. Large-scale models insist that Omar will degenerate to a remnant low in 24 hours, or less, and dissipate by Sunday morning. The NHC forecast will, once again, reflect this scenario. It appears that the slightly larger non-tropical low a few hundred miles to the east-northeast of Omar is causing the depression to move in an east-southeastward fashion at 9 kt. This binary interaction is only temporary, however, and Omar should return to an eastward track by Friday morning as the low pressure system downstream accelerates northeastward. Afterward, a turn toward the northeast is forecast early Saturday morning in response to an approaching frontal boundary from the northwest, and the Azores high several hundred miles to the east building southwestward over the central Atlantic. The official forecast is a little to the south of the previous advisory and is based on a blend of the various multi-model consensus aids. FORECAST POSITIONS AND MAX WINDS INIT 03/2100Z 35.4N 60.1W 30 KT 35 MPH 12H 04/0600Z 35.3N 58.8W 30 KT 35 MPH 24H 04/1800Z 35.3N 57.5W 25 KT 30 MPH...POST-TROP/REMNT LOW 36H 05/0600Z 36.3N 56.6W 25 KT 30 MPH...POST-TROP/REMNT LOW 48H 05/1800Z 37.5N 56.1W 20 KT 25 MPH...POST-TROP/REMNT LOW 60H 06/0600Z...DISSIPATED $$ Forecaster Roberts
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Tropical Storm Nana Forecast Discussion Number 10
2020-09-03 16:35:45| National Hurricane Center (Atlantic)
Issued at 1000 AM CDT Thu Sep 03 2020 000 WTNT41 KNHC 031435 TCDAT1 Tropical Storm Nana Discussion Number 10 NWS National Hurricane Center Miami FL AL162020 1000 AM CDT Thu Sep 03 2020 Satellite imagery indicates that Nana is weakening rapidly as it crosses northern Guatemala. There are no available observations near the center, so the initial intensity estimate of 40 kt is rather uncertain. Continued weakening is expected, and Nana is likely to be a remnant low pressure area by the time it reaches the Gulf of Tehuantepec in about 24 h. The global models continue to forecast conditions that are not conducive for Nana to re-intensify, so the intensity forecast calls for the remnant low to dissipate by 48 h even though it will be over water. The initial motion is 260/13 kt. A low- to mid-level ridge to the north of Nana should keep it moving on a west to west-southwestward track during the remainder of the cyclone's life. The new official forecast track is similar to the previous track and lies near the various consensus models, KEY MESSAGES: 1. Tropical storm conditions will continue near the center of Nana for a few more hours. 2. Heavy rainfall with isolated maximum amounts as high as 3 to 6 inches could result in flash flooding in Guatemala and portions of southeastern Mexico. FORECAST POSITIONS AND MAX WINDS INIT 03/1500Z 16.4N 90.3W 40 KT 45 MPH 12H 04/0000Z 16.0N 92.0W 30 KT 35 MPH...INLAND 24H 04/1200Z 15.4N 94.4W 25 KT 30 MPH...POST-TROP/REMNT LOW 36H 05/0000Z 14.9N 96.6W 20 KT 25 MPH...POST-TROP/REMNT LOW 48H 05/1200Z...DISSIPATED $$ Forecaster Beven
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Tropical Depression Omar Forecast Discussion Number 12
2020-09-03 16:35:45| National Hurricane Center (Atlantic)
Issued at 1100 AM AST Thu Sep 03 2020 721 WTNT45 KNHC 031435 TCDAT5 Tropical Depression Omar Discussion Number 12 NWS National Hurricane Center Miami FL AL152020 1100 AM AST Thu Sep 03 2020 Surprisingly, Omar's cloud pattern has changed little since it was classified as a tropical depression yesterday morning. A shapeless deep convective cloud mass still exists about 60 miles to the southeast of the sheared, exposed surface circulation center and the subjective T-numbers from TAFB and SAB are a carbon copy of the satellite intensity classifications 24 hours ago. Therefore, the initial intensity is once again held at 30 kt. The large-scale models as well as the statistical-dynamical intensity guidance show further weakening to a remnant low in 24 hours, and dissipation as soon as Saturday morning. Because of Omar's resiliency in such a harsh upper-level wind surrounding environment, the NHC forecast shows Omar holding onto depression status for another 12-18 hours, then finally degenerating to a remnant low Friday. The initial estimated motion hasn't changed either during the past 24 hours and is toward the east, or 085/11 kt within the deep-layer westerly flow provided by a subtropical ridge situated over the central Atlantic. This due east heading should continue through Friday morning, the a turn toward the east-northeast to northeast is forecast by Friday night in response to an approaching mid-latitude frontal zone. The official forecast is similar to the previous advisory and is based on the HFIP Corrected Consensus Approach model. FORECAST POSITIONS AND MAX WINDS INIT 03/1500Z 35.9N 61.1W 30 KT 35 MPH 12H 04/0000Z 35.8N 59.4W 30 KT 35 MPH 24H 04/1200Z 35.6N 57.7W 25 KT 30 MPH...POST-TROP/REMNT LOW 36H 05/0000Z 36.2N 56.5W 25 KT 30 MPH...POST-TROP/REMNT LOW 48H 05/1200Z 37.8N 55.3W 25 KT 30 MPH...POST-TROP/REMNT LOW 60H 06/0000Z...DISSIPATED $$ Forecaster Roberts
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