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Potential Tropical Cyclone Two Forecast Discussion Number 4
2019-07-11 10:46:54| National Hurricane Center (Atlantic)
Issued at 400 AM CDT Thu Jul 11 2019 000 WTNT42 KNHC 110846 TCDAT2 Potential Tropical Cyclone Two Discussion Number 4 NWS National Hurricane Center Miami FL AL022019 400 AM CDT Thu Jul 11 2019 The convective activity associated with the broad area of low pressure is still spread out, and the center of circulation is not well defined at this time. Both surface and scatterometer data indicate that the winds remain near 25 kt. The modest northerly shear affecting the system should not hamper further development. Overall, the environmental conditions still favor the formation of a tropical depression or a tropical storm later today, and as the system moves over warm waters, strengthening is indicated. The intensity models are not as aggressive as they were in previous runs, but still bring the disturbance to hurricane status in about 48 hour or so, as the disturbance approaches the coast. During the past several hours, the low pressure area has barely moved due to weak steering currents. However, a westward or 260 degrees drift at about 4 kt should begin soon. The system is heading toward a weakness in the ridge, and this pattern should induce a slow turn toward the west-northwest and then north during the next 3 to 5 days. The NHC track forecast continues to be located on the western edge of the guidance envelope, and it has been adjusted slightly eastward to be more consistent with the multi-model ensemble TVCA. It should be noted that track errors are typically larger for potential tropical cyclones than more mature systems. In addition, the run-to-run consistency in the track models has been poor, so confidence in the details of the forecast is not high at the moment. Key Messages: 1. A tropical depression is expected to form later today over the northern Gulf of Mexico. Conditions appear favorable for this system to strengthen to a hurricane that will bring storm surge, rainfall, and wind hazards to the central Gulf Coast. 2. A dangerous storm surge is possible in portions of southern and southeastern Louisiana where a Storm Surge Watch is in effect. Additional storm surge watches may be needed later today. Residents in these areas should monitor the progress of this system and listen to any advice given by local officials. 3. A Hurricane Watch is in effect for much of the Louisiana coast and additional tropical storm or hurricane watches and warnings could be required. Residents in the watch area should ensure they have their hurricane plan in place. 4. The slow movement of this system will result in a long duration heavy rainfall threat along the central Gulf Coast and inland through the lower Mississippi Valley through the weekend and potentially into early next week. Flash flooding and river flooding will become increasingly likely, some of which may be significant, especially along and east of the track of the system. FORECAST POSITIONS AND MAX WINDS INIT 11/0900Z 27.5N 88.2W 25 KT 30 MPH...POTENTIAL TROP CYCLONE 12H 11/1800Z 27.5N 88.7W 30 KT 35 MPH 24H 12/0600Z 27.7N 89.5W 40 KT 45 MPH 36H 12/1800Z 28.0N 90.3W 50 KT 60 MPH 48H 13/0600Z 28.5N 91.1W 65 KT 75 MPH 72H 14/0600Z 31.0N 91.7W 45 KT 50 MPH...INLAND 96H 15/0600Z 33.5N 92.0W 30 KT 35 MPH...INLAND 120H 16/0600Z 36.0N 90.9W 20 KT 25 MPH...POST-TROP/REMNT LOW $$ Forecaster Avila
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Potential Tropical Cyclone Two Forecast Discussion Number 3
2019-07-11 04:45:51| National Hurricane Center (Atlantic)
Issued at 1000 PM CDT Wed Jul 10 2019 000 WTNT42 KNHC 110245 TCDAT2 Potential Tropical Cyclone Two Discussion Number 3 NWS National Hurricane Center Miami FL AL022019 1000 PM CDT Wed Jul 10 2019 The system is becoming better organized, and it is almost a tropical depression. Satellite images show a persistent area of deep convection near the estimated center with loosely organized bands surrounding that feature. Earlier, the NOAA Hurricane Hunters found that the pressure has dropped a little to 1009 mb, although the center is not yet well defined. The estimated initial intensity is still 25 kt based on surface observations and the NOAA dropsonde data. The broad low is moving west-southwestward at about 8 kt. The track models are in general agreement that a mid-level ridge centered over the Rockies should cause the system to move slowly westward on Thursday and west-northwestward on Friday. After that time, however, the models diverge considerably with some solutions showing an abrupt northward turn toward a weakness in the ridge and others showing a more gradual one. The latest GFS run has shifted to the west of its previous track, closer to the previous NHC forecast, while the HWRF model has shifted to the right. Based on the overall guidance spread, this track forecast is nudged to the east of the previous forecast to be closer to the various consensus models, which typically are the most reliable. However, this forecast is still near the western edge of the model envelope. It should be noted that track errors are typically larger for potential tropical cyclones than more mature systems. In addition, the run-to-run consistency in the track models has been poor, so confidence in the details of the forecast is not high at the moment. Since the system is still in the formative stage, only slow strengthening is likely during the next 12 hours or so. However, after that time more significant strengthening is likely due to very warm SSTs across the northern Gulf of Mexico, a fairly moist atmosphere, and a favorable upper-level pattern over the system. The NHC intensity forecast is largely an update of the previous one and shows the system becoming a tropical storm on Thursday and a hurricane by late Friday. Additional strengthening is likely beyond the 48-hour point and the time it makes landfall, which is predicted to occur in a little less than 3 days. This forecast is fairly close to the IVCN and HCCA models. Key Messages: 1. A tropical depression is expected to form on Thursday over the northern Gulf of Mexico. Conditions appear favorable for this system to strengthen to a hurricane that will bring storm surge, rainfall, and wind hazards to the central Gulf Coast. 2. A dangerous storm surge is possible in portions of southern and southeastern Louisiana where a Storm Surge Watch is in effect. Additional storm surge watches may be needed on Thursday. Residents in these areas should monitor the progress of this system and listen to any advice given by local officials. 3. A Hurricane Watch is in effect for much of the Louisiana coast and additional tropical storm or hurricane watches and warnings could be needed on Thursday. Residents in the watch area should ensure they have their hurricane plan in place. 4. The slow movement of this system will result in a long duration heavy rainfall threat along the central Gulf Coast and inland through the lower Mississippi Valley through the weekend and potentially into early next week. Flash flooding and river flooding will become increasingly likely, some of which may be significant, especially along and east of the track of the system. FORECAST POSITIONS AND MAX WINDS INIT 11/0300Z 27.7N 88.0W 25 KT 30 MPH...POTENTIAL TROP CYCLONE 12H 11/1200Z 27.6N 88.6W 30 KT 35 MPH...TROPICAL CYCLONE 24H 12/0000Z 27.6N 89.5W 40 KT 45 MPH 36H 12/1200Z 27.9N 90.5W 50 KT 60 MPH 48H 13/0000Z 28.3N 91.3W 65 KT 75 MPH 72H 14/0000Z 30.2N 92.1W 60 KT 70 MPH...INLAND 96H 15/0000Z 32.8N 92.3W 35 KT 40 MPH...INLAND 120H 16/0000Z 35.5N 92.3W 20 KT 25 MPH...INLAND $$ Forecaster Cangialosi
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Potential Tropical Cyclone Two Forecast Discussion Number 2
2019-07-10 22:59:56| National Hurricane Center (Atlantic)
Issued at 400 PM CDT Wed Jul 10 2019 000 WTNT42 KNHC 102059 TCDAT2 Potential Tropical Cyclone Two Discussion Number 2 NWS National Hurricane Center Miami FL AL022019 400 PM CDT Wed Jul 10 2019 Data from An Air Force Reserve reconnaissance aircraft, surface observations, and satellite imagery indicate that the broad low pressure system located over the northeastern Gulf of Mexico still lacks a well-defined circulation center. Multiple low-level swirls associated with individual convective cells were noted in the aircraft wind data. However, shower and thunderstorm activity has been increasing over the past couple of hours in the previously convective-free northern semicircle, an indication that low-level wind field is beginning to improve in that region of the cyclone. Upper-level outflow has become well established except to the north where modest northerly wind shear is inhibiting the outflow. The initial intensity of 25 kt is based on earlier scatterometer wind data and recent recon winds of 25-30 kt to the south and west of the center. The initial motion estimate remains 245/07 kt. The latest model guidance continues in good agreement on the cyclone moving generally toward the west-southwest or southwest for the next 24 hours or so, followed by a westward motion on Friday. Afterwards, however, the model guidance diverges significantly. The 12Z ECMWF, GFS, HWRF, and HMON models have shifted farther east and turn the cyclone northwestward to northward in 48-72 hours, moving it inland along the south-central and southeastern coasts of Louisiana. In contrast, the UKMET has shifted farther west and keeps the system on more of westward track, taking it inland along the central Texas coast. The main difference is how the models handle the ridge to the north, with the ECMWF, GFS, HWRF, and HMON rapidly eroding the ridge as a weak shortwave trough passes to the north of the cyclone, whereas the UKMET shows the ridge not weakening as much due to the shortwave trough weakening as it lifts out to the east, which allows the ridge to remain intact. Due to this significant bifurcation in NHC's most reliable track model guidance, the best course of action is to slow down the forward speed and only make minor adjustments to the overall tack, which has been shifted slightly to the east, but not as far east as the simple consensus and HCCA models. Only slow strengthening is forecast for the next 24-36 hours due to the lack of a well-defined center and inner-core wind field, along with some modest northerly wind shear. By 48 hours and beyond, however, the combination of very low vertical wind shear, an impressive outflow pattern forecast by all of the global and regional models, and anomalously warm sea-surface temperatures of 30-31C should allow for significant intensification to hurricane strength before landfall occurs after 72 hours. Given that the system is still in the formative stages, the official intensity forecast remains a little below IVCN consensus through 48 hours and trends higher toward the ECMWF-based SHIPS guidance at 72 hours. Key Messages: 1. A tropical depression is expected to form by Thursday over the northern Gulf of Mexico. Conditions appear favorable for this system to strengthen to a hurricane that will bring storm surge, rainfall, and wind hazards to the central Gulf Coast. 2. A dangerous storm surge is possible in portions of southern and southeastern Louisiana where a Storm Surge Watch is in effect. Additional storm surge watches may be needed later tonight or tomorrow. Residents in these areas should monitor the progress of this system and listen to any advice given by local officials. 3. A Hurricane Watch has been issued for much of the Louisiana coast and additional tropical storm or hurricane watches could be needed later tonight or tomorrow. Residents in the watch area should ensure they have their hurricane plan in place. 4. The slow movement of this system will result in a long duration heavy rainfall threat along the central Gulf Coast and inland through the lower Mississippi Valley through the weekend and potentially into early next week. Flash flooding and river flooding will become increasingly likely, some of which may be significant, especially along and east of the track of the system. FORECAST POSITIONS AND MAX WINDS INIT 10/2100Z 28.1N 87.4W 25 KT 30 MPH...POTENTIAL TROP CYCLONE 12H 11/0600Z 27.7N 88.1W 30 KT 35 MPH...POTENTIAL TROP CYCLONE 24H 11/1800Z 27.5N 89.0W 35 KT 40 MPH...TROPICAL STORM 36H 12/0600Z 27.6N 90.2W 40 KT 45 MPH 48H 12/1800Z 28.2N 91.5W 55 KT 65 MPH 72H 13/1800Z 29.3N 92.4W 75 KT 85 MPH 96H 14/1800Z 31.9N 93.0W 55 KT 65 MPH...INLAND 120H 15/1800Z 34.8N 93.1W 25 KT 30 MPH...INLAND $$ Forecaster Stewart
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Potential Tropical Cyclone Two Forecast Discussion Number 1
2019-07-10 16:57:21| National Hurricane Center (Atlantic)
Issued at 1000 AM CDT Wed Jul 10 2019 000 WTNT42 KNHC 101457 TCDAT2 Potential Tropical Cyclone Two Discussion Number 1 NWS National Hurricane Center Miami FL AL022019 1000 AM CDT Wed Jul 10 2019 High-resolution satellite imagery along with surface and upper-air data indicate that the broad low pressure system located over the northeastern Gulf of Mexico has become a little better defined. The initial intensity of 25 kt is based on an average of 1-minute wind speeds of 20-33 kt reported by ships and buoys well south of the poorly defined center. Although the system is currently experiencing some northerly vertical wind shear, the shear is expected to gradually subside over the next day or so, and the low has a high chance of becoming a tropical depression or tropical storm by Thursday. Since this system has the potential to bring tropical storm conditions and storm surge to portions of the coast of Louisiana by late Thursday or Friday, Potential Tropical Cyclone advisories are being initiated at this time. The initial motion estimate is an uncertain 245/07 kt. Some erratic motion will be possible during the 24 hours or until a well-defined center develops. However, the general motion as indicated by the global and regional models is expected to be toward the west- southwest or southwest. By Friday, the cyclone is forecast to turn toward the west-northwest and then turn northwestward by Saturday into a developing break in a deep-layer ridge that currently extends from the southeastern U.S. westward across the southern Plains and into the Desert Southwest. The timing of the ridge breakdown owing to a shortwave trough moving southeastward out of the northern Plains will be critical since a later/earlier turn by the cyclone would shift the track west/east of the current forecast. The model guidance is widely divergent after 48 hours with the UKMET model the farthest west showing landfall along the Upper Texas coast, and the GFS and HMON models farther east with landfall in south-central Louisiana. The ECMWF model is about midway between these two extremes, and the official track forecast leans toward that model since it has performed well during this system's pre-development phase. Note that forecast uncertainty for disturbances is generally larger than for tropical cyclones, especially beyond 48-72 hours. Only slow strengthening is expected for the next 24-36 hours due to the lack of a well-defined center and inner-core wind field, along with some modest northerly wind shear. By 48 hours and beyond, however, the combination of atmospheric and oceanic conditions become ideal for intensification. The very low shear shear conditions, an impressive outflow pattern forecast by all of the global and regional models, and anomalously warm sea-surface temperatures of 30-31C argue for quick intensification, but given that the system is still in the formative stages, the official intensity forecast is a little below IVCN consensus through 48 hours and trends higher toward the ECMWF-based SHIPS guidance at 72 hours. Key Messages: 1. A tropical depression is expected to form later today or Thursday. Conditions appear favorable for this system to strengthen to a hurricane at it approaches the central Gulf Coast by the weekend. 2. Dangerous storm surge is possible in portions of southeast Louisiana, and a Storm Surge Watch has been issued for this area. The risk for dangerous storm surge impacts also exists farther west along the Louisiana coast into the Upper Texas coast, and additional storm surge watches may be needed later today or tonight. Residents in these areas should monitor the progress of this system and listen to any advice given by local officials. 3. A Tropical Storm Watch has been issued for portions of the Louisiana coast and additional Tropical Storm or Hurricane Watches could be needed later today or tonight for the remainder of the Louisiana coast and the Upper Texas Coast. 4. The system has the potential to produce very heavy rainfall along and inland of the central Gulf Coast through early next week. For more information, see products from your local National Weather Service office and the NOAA Weather Prediction Center. FORECAST POSITIONS AND MAX WINDS INIT 10/1500Z 28.5N 86.4W 25 KT 30 MPH...POTENTIAL TROP CYCLONE 12H 11/0000Z 27.9N 87.3W 25 KT 30 MPH...POTENTIAL TROP CYCLONE 24H 11/1200Z 27.5N 88.2W 30 KT 35 MPH...TROPICAL DEPRESSION 36H 12/0000Z 27.4N 89.3W 40 KT 45 MPH 48H 12/1200Z 27.6N 90.4W 50 KT 60 MPH 72H 13/1200Z 28.7N 92.3W 75 KT 85 MPH 96H 14/1200Z 30.7N 93.0W 65 KT 75 MPH...INLAND 120H 15/1200Z 32.6N 94.1W 30 KT 35 MPH...INLAND $$ Forecaster Stewart
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Tropical Depression Cosme Forecast Discussion Number 8
2019-07-08 10:34:43| National Hurricane Center (East Pacific)
Issued at 200 AM PDT Mon Jul 08 2019 000 WTPZ43 KNHC 080834 TCDEP3 Tropical Depression Cosme Discussion Number 8 NWS National Hurricane Center Miami FL EP032019 200 AM PDT Mon Jul 08 2019 Cosme continues to gradually weaken over 23 to 24 degree C waters and in a dry and stable atmospheric environment with about 10 to 15 kt of westerly shear. The depression now consists of scattered mid- to high- level debris clouds over a low-level swirl, with a small area of convection located nearly 200 n mi northeast the system's center. A scatterometer pass at 0450 UTC showed peak winds of 25 kt associated with Cosme's circulation. This intensity agrees with the satellite intensity estimates from TAFB and ADT and will be the depression's initial intensity for this advisory. The unfavorable environmental conditions for Cosme will not improve as the depression continues to move over cooler waters today. This should prevent any significant amounts of deep convection from developing near the system's center, and Cosme is expected to become a remnant low at some point later on today. The initial motion of Cosme is northwest at 8 kt. This general motion will continue through today with a slowing in forward speed. Thereafter, the remnant low will drift northwestward to west-northwestward in the low-level flow until it dissipates. FORECAST POSITIONS AND MAX WINDS INIT 08/0900Z 19.8N 120.1W 25 KT 30 MPH 12H 08/1800Z 20.4N 120.8W 25 KT 30 MPH...POST-TROP/REMNT LOW 24H 09/0600Z 21.0N 121.5W 25 KT 30 MPH...POST-TROP/REMNT LOW 36H 09/1800Z 21.5N 122.2W 20 KT 25 MPH...POST-TROP/REMNT LOW 48H 10/0600Z...DISSIPATED $$ Forecaster Latto/Pasch
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