Tropical Storm Rene

Tropical Storm Rene Remnant Track 1700 Hours September 14 2020
Tropical Storm Rene Remnant Track 1700 Hours September 14 2020

Tropical Depression Rene Wind Speed FieldTropical Storm ReneNWS National Hurricane Center Miami FL 500 PM AST Mon Sep 14, 2020 (see Monday video below)

Visible satellite imagery during the past few hours shows that Rene has opened into a trough of low pressure and is no longer a tropical cyclone. Therefore, this is the last advisory. The remnants of Rene will likely move generally southwestward for the next day or two while the associated winds slowly subside.

Although the trough may continue to produce occasional showers and thunderstorms, no redevelopment of the system is expected.

FORECAST POSITIONS AND MAX WINDS

INIT  14/2100Z 26.9N  49.3W   25 KT  30 MPH...REMNANTS OF RENE
 12H  15/0600Z...DISSIPATED

NWS National Hurricane Center Miami FL 1100 AM AST Mon Sep 14, 2020 

Deep convection continues to pulse over the eastern portion of Rene’s circulation, enough to maintain the system’s status as a tropical cyclone. However, recent visible statellite imagery suggest that the circulation may not be as well defined as it was yesterday. Satellite classifications support an initial wind speed of 25 kt. Strong west-northwesterly shear and dry air are expected to cause the depression to weaken and degenerate into a remnant low within the next 12-24 hours. The global models show the low-level circulation dissipating within 2 to 3 days and so does the official forecast.

Rene has moved very little overnight but a west-southwestward or southwestward motion within the low-level steering flow should begin soon. That general motion is expected to continue until dissipation in a day or two.

FORECAST POSITIONS AND MAX WINDS

INIT  14/1500Z 27.5N  48.3W   25 KT  30 MPH - Depression (ESE St. George's, Bermuda)
 12H  15/0000Z 27.0N  49.1W   25 KT  30 MPH - Low (ESE St. George's, Bermuda)
 24H  15/1200Z 26.4N  50.1W   20 KT  25 MPH - Low (ESE St. George's, Bermuda)
 36H  16/0000Z 25.5N  51.4W   20 KT  25 MPH - Low (ESE St. George's, Bermuda)
 48H  16/1200Z 24.6N  53.5W   20 KT  25 MPH - Low (ESE St. George's, Bermuda)
 60H  17/0000Z...DISSIPATED

NWS National Hurricane Center Miami FL 1100 PM AST Sun Sep 13, 2020 

Rene continues to produced puffs of deep convection that are continually being sheared away by nearly 30 kt of westerly shear. These brief convective bursts have not been sufficiently organized to warrant a Dvorak classification for about 12 hours, so if the convective organization does not increase soon, Rene could become a remnant low tonight. Continued shear and a very dry mid-level environment should result in Rene’s remnants dissipating by 60 hours, if not sooner.

Rene’s forward speed has slowed since the last advisory, with a westward drift of 270/02 the current estimate. The shallow cyclone should accelerate west-southwestward or southwestward in the low-level flow by 24 hours and continue on that general motion until dissipation. The new NHC track forecast is adjusted south of the previous one toward the new multi-model consensus.

FORECAST POSITIONS AND MAX WINDS

INIT  14/0300Z 27.2N  47.9W   25 KT  30 MPH - Depression (ESE St. George's, Bermuda)
 12H  14/1200Z 27.3N  48.3W   25 KT  30 MPH - Low (ESE St. George's, Bermuda)
 24H  15/0000Z 26.9N  49.1W   20 KT  25 MPH - Low (ESE St. George's, Bermuda)
 36H  15/1200Z 26.2N  50.2W   20 KT  25 MPH - Low (ESE St. George's, Bermuda)
 48H  16/0000Z 25.5N  51.4W   20 KT  25 MPH - Low (ESE St. George's, Bermuda)
 60H  16/1200Z...DISSIPATED

NWS National Hurricane Center Miami FL 500 PM AST Sun Sep 13, 2020

Rene continues to produce occasional small bursts of deep convection, most recently to the north of its surface center. Both the TAFB and SAB Dvorak classifications indicated that convection at 18Z was insufficient to classify the system, an indication that the few pop up thunderstorms are not sufficiently organized to classify the system as a tropical cyclone. That said, convection has increased a little since that time and there is a possibility that deep convection could increase further this evening. While Rene is still a tropical depression for the moment, if its convection does not persist, it could become a remnant low as soon as tonight.

Only very small changes were made to the NHC track and intensity forecasts. Rene’s forward speed has continued to slow down since this morning. The shallow cyclone should make a westward and then southwestward turn during the next day or two, steered by a building low-level ridge to the north. Regardless of its exact status, Rene will probably continue to produce only a few small disorganized bursts of convection for the next few days while its circulation gradually spins down. Surrounding dry air and large-scale subsidence will likely prevent the redevelopment of more signifcant shower or thunderstorm activity. Most of the dynamical guidance indicates that Rene will open into a trough of low pressure within about 72 h, if not sooner and the NHC forecast shows likewise.

FORECAST POSITIONS AND MAX WINDS

INIT  13/2100Z 27.3N  47.6W   25 KT  30 MPH - Depression (ESE St. George's, Bermuda)
 12H  14/0600Z 27.7N  48.1W   25 KT  30 MPH - Depression (ESE St. George's, Bermuda)
 24H  14/1800Z 27.4N  48.7W   20 KT  25 MPH - Low (ESE St. George's, Bermuda)
 36H  15/0600Z 26.9N  49.6W   20 KT  25 MPH - Low (ESE St. George's, Bermuda)
 48H  15/1800Z 26.3N  50.7W   20 KT  25 MPH - Low (ESE St. George's, Bermuda)
 60H  16/0600Z 25.7N  52.0W   20 KT  25 MPH - Low (ESE St. George's, Bermuda)
 72H  16/1800Z...DISSIPATED

NWS National Hurricane Center Miami FL 1100 AM AST Sun Sep 13, 2020 

Sporadic small areas of convection continue to fire off around the circulation of Rene, only to dissipate shortly thereafter. A recent ASCAT overpass showed an area of 20 to 25 kt winds in the eastern semicircle. Therefore, the initial intensity will remain 25 kt. The dry environment surrounding Rene will only get drier over the next couple of days. That, along with increasing subsidence over the cyclone should eventually cause Rene to become a remnant low. There is no change to the previous forecast intensity or timing of the system becoming a remnant low, which is consistent with the global models.

Rene is beginning to slow down as a ridge starts to build to the north and northwest of the cyclone. This slowing trend should continue through tonight. Late Monday through Tuesday, a turn to the west then southwest should occur as whatever remains of the system becomes steered by the larger circulation of Tropical Depression Twenty to its southwest. There is little change to the previous track forecast, and the latest NHC forecast lies near the various multi-model track consensus guidance.

FORECAST POSITIONS AND MAX WINDS

INIT  13/1500Z 26.8N  47.6W   25 KT  30 MPH - Depression (ESE St. George's, Bermuda)
 12H  14/0000Z 27.5N  48.3W   25 KT  30 MPH - Depression (ESE St. George's, Bermuda)
 24H  14/1200Z 27.6N  48.8W   25 KT  30 MPH - Depression (ESE St. George's, Bermuda)
 36H  15/0000Z 27.3N  49.6W   20 KT  25 MPH - Low (ESE St. George's, Bermuda)
 48H  15/1200Z 26.7N  50.5W   20 KT  25 MPH - Low (ESE St. George's, Bermuda)
 60H  16/0000Z 26.1N  51.5W   20 KT  25 MPH - Low (ESE St. George's, Bermuda)
 72H  16/1200Z...DISSIPATED

NWS National Hurricane Center Miami FL 1100 PM AST Sat Sep 12, 2020 

Satellite images indicate that a band of convection has recently increased on the western side of the circulation, otherwise the center remains mostly exposed. The initial wind speed is reduced to 25 kt based on scatterometer data. The small cyclone is likely to gradually spin down due to persistent moderate shear and a fairly dry environment. The hostile conditions are not likely to change too much, so Rene is forecast to lose all convection in a day or two and become a remnant low. The new NHC intensity forecast is lower than the previous one due to the weaker initial intensity and follows the latest global model consensus.

The depression is moving northwestward at about 11 kt. A blocking ridge of high pressure is forecast to build to the northwest or Rene, causing the cyclone to slow down and then turn westward and west-southwestward early next week. The guidance is similar to the previous package, and no significant track changes were made to the official NHC forecast. The forecast still might hold onto the circulation too long, and the remnant low could dissipate into a trough of low pressure sooner than indicated below.

FORECAST POSITIONS AND MAX WINDS

INIT  13/0300Z 25.3N  46.4W   25 KT  30 MPH - Depression (ESE St. George's, Bermuda)
 12H  13/1200Z 26.4N  47.3W   25 KT  30 MPH - Depression (ESE St. George's, Bermuda)
 24H  14/0000Z 27.3N  48.1W   25 KT  30 MPH - Depression (ESE St. George's, Bermuda)
 36H  14/1200Z 27.4N  48.6W   20 KT  25 MPH - Low (ESE St. George's, Bermuda)
 48H  15/0000Z 27.2N  49.3W   20 KT  25 MPH - Low (ESE St. George's, Bermuda)
 60H  15/1200Z 26.5N  50.5W   20 KT  25 MPH - Low (ESE St. George's, Bermuda)
 72H  16/0000Z...DISSIPATED

NWS National Hurricane Center Miami FL 500 PM AST Sat Sep 12, 2020 

A fragmented band of deep convection has recently developed over the northern portion of the circulation, but the associated cloud tops are already warming, suggesting that dry air is continuing to hinder development. Dvorak classifications of T2.0 (30 kt) from both TAFB and SAB, and the earlier ASCAT data are the basis for the 30-kt initial intensity.

The depression is expected to remain within an area of dry mid-level air and increasing west- northwesterly shear on Sunday, and these factors are likely to contribute to gradual weakening over the next couple of days. While the shear is forecast to abate later in the period, the SHIPS guidance indicates mid-level relative humidity values of 30-40 percent, which suggest weakening is likely to continue. The global models also weaken the system with the UK and ECMWF showing dissipation within 4-5 days. The new NHC intensity forecast is again lowered from before and now calls for Rene to become a remnant low in 72 h and dissipate by day 5. Both of these events, however, could occur much sooner.

Rene is moving northwestward at about 12 kt. A blocking ridge of high pressure is forecast to build to the northwest of Rene on Sunday which is expected to considerably slow the forward progress of the cyclone. As the ridge continues to shift eastward and build, Rene or its remnants are forecast to turn west-southwestward in the low-level steering flow early next week. The overall guidance envelope as changed little from this morning, and the new NHC track forecast is essentially an update of the previous advisory.

FORECAST POSITIONS AND MAX WINDS

INIT  12/2100Z 24.3N  45.6W   30 KT  35 MPH - Depression (ESE St. George's, Bermuda)
 12H  13/0600Z 25.6N  46.7W   30 KT  35 MPH - Depression (ESE St. George's, Bermuda)
 24H  13/1800Z 26.9N  47.7W   30 KT  35 MPH - Depression (ESE St. George's, Bermuda)
 36H  14/0600Z 27.4N  48.3W   25 KT  30 MPH - Depression (ESE St. George's, Bermuda)
 48H  14/1800Z 27.2N  48.8W   25 KT  30 MPH - Depression (ESE St. George's, Bermuda)
 60H  15/0600Z 26.7N  49.6W   25 KT  30 MPH - Depression (ESE St. George's, Bermuda)
 72H  15/1800Z 25.8N  51.0W   20 KT  25 MPH - Low (ESE St. George's, Bermuda)
 96H  16/1800Z 24.7N  54.0W   20 KT  25 MPH - Low (ESE St. George's, Bermuda)
120H  17/1800Z...DISSIPATED

NWS National Hurricane Center Miami FL 1100 AM AST Sat Sep 12, 2020 

The deep convection associated with Rene has gradually decreased over the past several hours, with only a few sporadic patches remaining. A recent ASCAT overpass showed peak winds of 28 kt in the northeastern quadrant, while the latest Dvorak intensity estimates from TAFB and SAB suggest the system is 30 kt. Therefore the initial intensity is being lowered to 30 kt. The depression is forecast to battle dry air for the next several days, with SHIPS guidance indicating that the mid-level relative humidity will decrease to under 40 percent in a few days. Also, it appears that there will be increasing subsidence over the system starting in a couple of days due to a ridge building to the northwest of the cyclone. Neither of these conditions bode well for maintaining organized deep convection. And, with it anticipated that the depression will struggle to maintain convection it is expected to slowly spin down over the next several days.

The official forecast shows Rene degenerating into a remnant low in 5 days, but that timing is low confidence, as the system may generate just enough convection over warm waters to continue to be classified as a tropical cyclone longer than that. The alternative scenario is that the system could become a remnant low or open into a trough even sooner. The NHC intensity forecast is a little lower than the previous one mainly due to the decrease in initial intensity, and is in good agreement with the various intensity consensus values.

Rene continues to move northwestward, now at 11 kt. A northwestward motion around the western periphery of a mid-level ridge over the eastern Atlantic should continue into tonight. On Sunday, Rene is forecast to slow down as the ridge builds to the northwest and north of the cyclone. By Tuesday, Rene is expected to turn westward and then west-southwestward to southwestward under the influence of the building ridge. The NHC track forecast is very little changed from the previous one, and is near the middle of the track guidance.

FORECAST POSITIONS AND MAX WINDS

INIT  12/1500Z 23.2N  44.4W   30 KT  35 MPH - Depression (WSW Cape Verde Islands)
 12H  13/0000Z 24.5N  45.8W   30 KT  35 MPH - Depression (WSW Cape Verde Islands)
 24H  13/1200Z 26.0N  47.0W   30 KT  35 MPH - Depression (WSW Cape Verde Islands)
 36H  14/0000Z 27.0N  47.7W   30 KT  35 MPH - Depression (WSW Cape Verde Islands)
 48H  14/1200Z 27.3N  48.2W   25 KT  30 MPH - Depression (ESE St, Georges, Bermuda)
 60H  15/0000Z 27.0N  48.7W   25 KT  30 MPH - Depression (ESE St, Georges, Bermuda)
 72H  15/1200Z 26.3N  49.8W   25 KT  30 MPH - Depression (ESE St, Georges, Bermuda)
 96H  16/1200Z 25.0N  52.6W   25 KT  30 MPH - Depression (ESE St, Georges, Bermuda)
120H  17/1200Z 24.0N  56.0W   25 KT  30 MPH - Low (ESE St, Georges, Bermuda)

NWS National Hurricane Center Miami FL 1100 PM AST Fri Sep 11, 2020 

Deep convection has persisted near the center of Rene since this afternoon and a couple of earlier microwave overpasses suggest that there has been an increase in banding over the southwestern portion of the circulation. Despite what appears to be an increase in organization, recent ASCAT data indicated that this has not translated into an increase in intensity. The scatterometer data still supports an initial wind speed of 35 kt. Environmental conditions are forecast to generally be conducive for some strengthening over the next 12-24 hours, however with Rene continuing to struggle to intensify the NHC wind speed prediction has again been reduced during the that time. By 36-48 hours, Rene is expected to move beneath an area of strong upper-level west-northwesterly flow, and this increase in shear is expected to cause weakening. The ECMWF and GFS models significantly weaken Rene after 72 hours, with the ECMWF showing dissipation before the end of the forecast period. For now, the official forecast calls for Rene to weaken to a tropical depression by day 4, but it is possible that the system will degenerate into a trough of low pressure before day 5.

Rene is moving west-northwestward or 295/12 kt. The cyclone should turn toward the northwest as it moves around the western portion of a mid-level ridge over the eastern Atlantic. In a couple of days, a mid-level high is predicted to build to the northwest of Rene, which should cause the cyclone to slow down and turn westward, and then west-southwestward later in the forecast period. The track guidance is in fairly good agreement and the various consensus aids remained close to the previous official forecast. Therefore, the new NHC forecast is essentially an update of the previous advisory.

FORECAST POSITIONS AND MAX WINDS

INIT  12/0300Z 21.4N  42.4W   35 KT  40 MPH - Tropical Storm (WSW Cape Verde Islands)
 12H  12/1200Z 22.4N  44.0W   35 KT  40 MPH - Tropical Storm (WSW Cape Verde Islands)
 24H  13/0000Z 24.1N  45.8W   40 KT  45 MPH - Tropical Storm (WSW Cape Verde Islands)
 36H  13/1200Z 25.7N  47.0W   40 KT  45 MPH - Tropical Storm (WSW Cape Verde Islands)
 48H  14/0000Z 26.8N  47.6W   40 KT  45 MPH - Tropical Storm (WSW Cape Verde Islands)
 60H  14/1200Z 27.1N  47.8W   35 KT  40 MPH - Tropical Storm (ESE St, Georges, Bermuda)
 72H  15/0000Z 26.8N  48.4W   35 KT  40 MPH - Tropical Storm (ESE St, Georges, Bermuda)
 96H  16/0000Z 25.9N  50.9W   30 KT  35 MPH - Low (ESE St, Georges, Bermuda)
120H  17/0000Z 24.8N  54.0W   30 KT  35 MPH - Low (ESE St, Georges, Bermuda)

NWS National Hurricane Center Miami FL 500 PM AST Fri Sep 11, 2020 

Deep convection has increased over the western semicircle of the circulation and is re-forming near the center. Based on a blend of subjective Dvorak classifications and ADT values from UW-CIMSS, the current intensity estimate remains at 35 kt. Hopefully we will get a scatterometer pass over the system soon to give a better intensity estimate. Some strengthening is anticipated during the next day or so, but increasing shear should halt the intensification process, and bring about weakening, thereafter. The official intensity forecast is above the latest model consensus.

Rene continues to move west-northwestward and should gradually turn to the right while it moves around the western periphery of a mid-level high pressure system for the next couple of days. In the latter half of the forecast period, a blocking high to the north and northwest of Rene should force the cyclone to turn toward the west and west-southwest. The new official track forecast has been shifted to the southwest of the previous one in 3-5 days, following the latest guidance. [ NOTE: NWS 5:00 pm graphic not posted]

FORECAST POSITIONS AND MAX WINDS

INIT  11/2100Z 20.7N  41.1W   35 KT  40 MPH - Depression (WSW Cape Verde Islands)
 12H  12/0600Z 21.7N  42.8W   40 KT  45 MPH - Tropical Storm (WSW Cape Verde Islands)
 24H  12/1800Z 23.3N  44.8W   45 KT  50 MPH - Tropical Storm (WSW Cape Verde Islands)
 36H  13/0600Z 24.9N  46.4W   45 KT  50 MPH - Tropical Storm (WSW Cape Verde Islands)
 48H  13/1800Z 26.4N  47.3W   45 KT  50 MPH - Tropical Storm (WSW Cape Verde Islands)
 60H  14/0600Z 27.0N  47.4W   40 KT  45 MPH - Tropical Storm (ESE St, Georges, Bermuda)
 72H  14/1800Z 27.0N  48.0W   40 KT  45 MPH - Tropical Storm (ESE St, Georges, Bermuda)
 96H  15/1800Z 26.5N  50.0W   35 KT  40 MPH - Tropical Storm (ESE St, Georges, Bermuda)
120H  16/1800Z 25.0N  53.0W   35 KT  40 MPH - Tropical Storm (ESE St, Georges, Bermuda)

NWS National Hurricane Center Miami FL 1100 AM AST Fri Sep 11, 2020 

Rene lost essentially all of its deep convection over the past several hours, however recently some new thunderstorms have developed over the western part of the circulation. The cause of the system’s decline is not clear. One negative environmental factor could be dry air, since the SHIPS output based on the GFS model shows mid-level relative humidities of 50-55 percent. Using a blend of Dvorak current intensity estimates from TAFB and SAB along with objective ADT values from UW-CIMSS gives a rather uncertain advisory intensity of 35 kt. Since the cyclone should remain over waters of 26.5 deg C or warmer and the shear is not expected to increase much during the next day or two, some re-intensification is expected.

Based on the current state of Rene, the official intensity forecast is revised downward to show less strengthening through 48 hr compared to the previous predictions. By the latter part of the forecast period, increasing northwesterly shear should result in weakening. The NHC forecast is above most of the intensity guidance.

The latest center fixes give a slightly faster west-northwestward motion of 290/11 kt. Rene should continue to move around the western periphery of a mid-level anticyclone for the next couple of days. Then, a high-pressure area building to the north and northwest of the cyclone should induce a slowing of the forward speed and a turn toward the left. The official track forecast is similar to the previous one and closely aligned with the NOAA corrected consensus, HCCA, prediction.

FORECAST POSITIONS AND MAX WINDS

INIT  11/1500Z 20.3N  39.9W   35 KT  40 MPH - Tropical Storm (WSW Cape Verde Islands)
 12H  12/0000Z 21.2N  41.5W   40 KT  45 MPH - Tropical Storm (WSW Cape Verde Islands)
 24H  12/1200Z 22.5N  43.6W   45 KT  50 MPH - Tropical Storm (WSW Cape Verde Islands)
 36H  13/0000Z 24.3N  45.3W   50 KT  60 MPH - Tropical Storm (WSW Cape Verde Islands)
 48H  13/1200Z 25.9N  46.4W   50 KT  60 MPH - Tropical Storm (WSW Cape Verde Islands)
 60H  14/0000Z 27.0N  46.7W   45 KT  50 MPH - Tropical Storm (WSW Cape Verde Islands)
 72H  14/1200Z 27.3N  46.8W   45 KT  50 MPH - Tropical Storm (ESE St, Georges, Bermuda)
 96H  15/1200Z 26.8N  47.8W   40 KT  45 MPH - Tropical Storm (ESE St, Georges, Bermuda)
120H  16/1200Z 26.8N  51.0W   35 KT  40 MPH - Tropical Storm (ESE St, Georges, Bermuda)

NWS National Hurricane Center Miami FL 1100 PM AST Thu Sep 10, 2020 

Microwave satellite images from late this afternoon and evening shows that the center of Rene is located slightly northeast of the main convective mass. This appears to be due to some easterly flow that is undercutting the outflow layer. Dvorak CI numbers from both SAB and TAFB remain 3.0 (45 kt) but the SAB T-number has decreased slightly, and a recent ASCAT overpass suggests that the winds are not as strong as previously estimated. The ASCAT data revealed peak winds of 30-35 kt, so the initial intensity has been adjusted to 40 kt, which could be a little generous.

The upper-level wind pattern is expected to become favorable for strengthening while the cyclone moves over marginally warm sea surface temperatures during the next day or two. This should allow for some modest strengthening during that time, but the statistical guidance is not as bullish as before. Therefore the intensity forecast has been lowered slightly, and if strengthening does not occur soon additional downward adjustments to the intensity prediction may be needed. By 60 h, Rene is forecast to move into an area of strong west-northwesterly shear, which is expected to weaken the cyclone during the latter portion of the forecast period.

Rene continues moving west-northwestward with a motion of 290/10 kt. The cyclone is approaching the western periphery of a mid-level ridge over the eastern Atlantic and Rene is forecast to turn northwestward and then north-northwestward over the next few days. Later in the period, a ridge is forecast to build to the northwest of the tropical cyclone and Rene’s forward motion is expected to slow considerably early next week. There is a fair amount of model spread by 96 and 120 h, with some of the global models taking Rene more northeastward during that time. The NHC forecast continues to lie close to the various consensus aids, and indicates a fairly slow forward speed on days 3-5.

FORECAST POSITIONS AND MAX WINDS

INIT  11/0300Z 19.3N  37.6W   40 KT  45 MPH - Tropical Storm (WSW Cape Verde Islands)
 12H  11/1200Z 19.8N  39.1W   45 KT  50 MPH - Tropical Storm (WSW Cape Verde Islands)
 24H  12/0000Z 20.7N  41.1W   50 KT  60 MPH - Tropical Storm (WSW Cape Verde Islands)
 36H  12/1200Z 22.0N  43.1W   55 KT  65 MPH - Tropical Storm (WSW Cape Verde Islands)
 48H  13/0000Z 23.7N  44.9W   60 KT  70 MPH - Tropical Storm (WSW Cape Verde Islands)
 60H  13/1200Z 25.2N  46.1W   60 KT  70 MPH - Tropical Storm (WSW Cape Verde Islands)
 72H  14/0000Z 26.4N  46.9W   55 KT  65 MPH - Tropical Storm (ESE St, Georges, Bermuda)
 96H  15/0000Z 27.3N  47.5W   45 KT  50 MPH - Tropical Storm (ESE St, Georges, Bermuda)
120H  16/0000Z 27.5N  49.7W   40 KT  45 MPH - Tropical Storm (ESE St, Georges, Bermuda)

NWS National Hurricane Center Miami FL 500 PM AST Thu Sep 10, 2020 

It appeared that the storm had become better organized this morning, but that development trend seems to have been at least temporarily interrupted. Rene’s central features have become rather ragged-looking, and deep convection has diminished somewhat. It appears that the system is being disrupted a bit by easterly flow that is undercutting the outflow layer. There is also an apparent dearth of low-level inflow over the southern and southeastern portions of the circulation at this time. Dvorak intensity estimates from both TAFB and SAB remain T3.0/45 kt, so the current intensity estimate is unchanged from the previous advisory. Assuming that the upper-level winds will soon become a little more conducive for strengthening, Rene is forecast to become a hurricane by the weekend. The official intensity forecast is a little below the latest model consensus.

Rene continues its west-northwestward movement with a motion of near 285/10 kt. The cyclone is expected to turn northwestward and then north-northwestward for the next few days, while moving around the western periphery of a mid-level anticyclone. Later in the forecast period, A mid-level high is predicted to build to the northwest of Rene, which should slow down the cyclone’s forward progress and cause it to turn to the left. At the present time, it appears that Rene will remain sufficiently separated from Paulette, which is located about 800 n mi to the west, for there not to be a significant binary interaction between the two storms. The official track forecast remains close to the simple dynamical model consensus, TVCN.

FORECAST POSITIONS AND MAX WINDS

INIT  10/2100Z 18.9N  36.8W   45 KT  50 MPH - Tropical Storm (WSW Cape Verde Islands)
 12H  11/0600Z 19.4N  38.1W   50 KT  60 MPH - Tropical Storm (WSW Cape Verde Islands)
 24H  11/1800Z 20.2N  40.1W   55 KT  65 MPH - Tropical Storm (WSW Cape Verde Islands)
 36H  12/0600Z 21.3N  42.2W   60 KT  70 MPH - Tropical Storm (WSW Cape Verde Islands)
 48H  12/1800Z 22.7N  44.1W   65 KT  75 MPH - Category 1 (WSW Cape Verde Islands)
 60H  13/0600Z 24.3N  45.7W   65 KT  75 MPH - Category 1 (WSW Cape Verde Islands)
 72H  13/1800Z 25.8N  46.7W   60 KT  70 MPH - Tropical Storm (WSW Cape Verde Islands)
 96H  14/1800Z 27.3N  47.5W   50 KT  60 MPH - Tropical Storm (ESE St, Georges, Bermuda)
120H  15/1800Z 27.5N  49.5W   45 KT  50 MPH - Tropical Storm (ESE St, Georges, Bermuda)

NWS National Hurricane Center Miami FL 1100 AM AST Thu Sep 10, 2020 

Vertical shear appears to have lessened somewhat over Rene, with the estimated center more embedded within the convective cloud mass. The storm has also developed a better defined anticyclonic outflow pattern. Dvorak intensity estimates from both TAFB and SAB are 45 kt, and that will be used for the advisory intensity. Since the vertical shear is not expected to be strong for the next 48 hours or so, gradual strengthening is anticipated during that time, and Rene is forecast to become a hurricane by Saturday. This is in reasonable agreement with the latest intensity model consensus, IVCN. In the latter half of the forecast period, increased westerly shear over the tropical cyclone is expected, which should lead to weakening.

Rene continues on a west-northwestward track, and is moving at about 285/10 kt. The tropical cyclone is currently located on the southwest side of a mid-level ridge over the eastern Atlantic. Over the next few days, Rene should move around the western periphery of this ridge and turn from a west-northwestward to a north-northwestward heading. Around the end of the forecast period, a high building to the northwest of the cyclone will likely cause a significant slowing of the forward speed. The official track forecast is a little left of the previous one to be in better agreement with the latest model consensus predictions.

FORECAST POSITIONS AND MAX WINDS

INIT  10/1500Z 18.6N  35.8W   45 KT  50 MPH - Tropical Storm (WSW Cape Verde Islands)
 12H  11/0000Z 19.0N  37.2W   50 KT  60 MPH - Tropical Storm (WSW Cape Verde Islands)
 24H  11/1200Z 19.6N  39.3W   55 KT  65 MPH - Tropical Storm (WSW Cape Verde Islands)
 36H  12/0000Z 20.4N  41.4W   60 KT  70 MPH - Tropical Storm (WSW Cape Verde Islands)
 48H  12/1200Z 21.7N  43.6W   65 KT  75 MPH - Category 1 (WSW Cape Verde Islands)
 60H  13/0000Z 23.1N  45.6W   65 KT  75 MPH - Category 1 (WSW Cape Verde Islands)
 72H  13/1200Z 24.7N  47.2W   60 KT  70 MPH - Tropical Storm (WSW Cape Verde Islands)
 96H  14/1200Z 27.6N  49.3W   50 KT  60 MPH - Tropical Storm (ESE St, Georges, Bermuda)
120H  15/1200Z 29.2N  50.3W   40 KT  45 MPH - Tropical Storm (ESE St, Georges, Bermuda)

NWS National Hurricane Center Miami FL 1100 PM AST Wed Sep 09, 2020 

Rene remains a sheared tropical cyclone, with modest mid-/upper-level easterly vertical wind shear of 12-15 kt undercutting the otherwise favorable outflow layer. The combination of the shear and intrusions of dry mid-level air have caused the convective pattern to continue to fluctuate since the previous advisory. Although a recent burst of deep convection has again pulsed near and to he west of the center, the intensity is being maintained at 35 kt based on a 09/2305Z ASCAT-A overpass indicating barely 34 kt winds in the northwest quadrant. The 34-kt wind radius was also expanded in that quadrant based on the ASCAT wind data.

The initial motion remains west-northwestward motion or 285/11 kt. Under the influence of a mid-level ridge, Rene is expected to continue moving west-northward over the eastern Atlantic for the next few days. A weakness in the ridge is forecast to develop around 40W-45W longitude, which will be partly induced by Tropical Storm Paulette’s circulation, causing Rene to slow down and turn toward the northwest and then north-northwest on 3-4 days. By day 5, Rene’s northward motion is forecast to be blocked significantly by a building ridge to the north of the cyclone as TS Paulette moves farther away. It is possible that Rene could stall or even make a small looping motion if the storm gets trapped within the much larger ridge. The new NHC forecast is to the left or south of the previous advisory track, but not as far left as the consensus models or the preponderance of the remaining guidance.

Rene’s upper-level outflow is forecast to remain intact for the next 60 h or so, which would should allow for at least gradual strengthening during that time. The shear is forecast by both the GFS and the ECMWF models to decrease to near zero in the 36-48 h time frame, and that is when Rene should be able to take advantage of marginal sea-surface temperatures (SST) of 26.5C and modest mid-level humidity conditions, and obtain hurricane status in 48-60 h. Thereafter, strong west-northwesterly shear is expected to induce gradual weakening despite the cyclone moving over warmer SSTs of 27-28C. The official intensity forecast is similar to the GFS model intensity forecast, and lies below the simple consensus model IVCN and the corrected-consensus models HCCA and FSSE.

FORECAST POSITIONS AND MAX WINDS

INIT  10/0300Z 18.0N  34.0W   35 KT  40 MPH - Tropical Storm (WSW Cape Verde Islands)
 12H  10/1200Z 18.4N  35.5W   40 KT  45 MPH - Tropical Storm (WSW Cape Verde Islands)
 24H  11/0000Z 18.9N  37.4W   45 KT  50 MPH - Tropical Storm (WSW Cape Verde Islands)
 36H  11/1200Z 19.4N  39.3W   50 KT  60 MPH - Tropical Storm (WSW Cape Verde Islands)
 48H  12/0000Z 20.5N  41.4W   60 KT  70 MPH - Tropical Storm (WSW Cape Verde Islands)
 60H  12/1200Z 21.8N  43.2W   65 KT  75 MPH - Category 1 (WSW Cape Verde Islands)
 72H  13/0000Z 23.5N  45.1W   60 KT  70 MPH - Tropical Storm (WSW Cape Verde Islands)
 96H  14/0000Z 26.8N  46.5W   50 KT  60 MPH - Tropical Storm (ESE St, Georges, Bermuda)
120H  15/0000Z 28.3N  47.6W   40 KT  45 MPH - Tropical Storm (ESE St, Georges, Bermuda)

NWS National Hurricane Center Miami FL 500 PM AST Wed Sep 09, 2020 

Although the cloud pattern of Rene has changed little in overall organization since earlier today, there are some indications that the easterly shear over the storm has diminished somewhat. Cirrus cloud motions show that upper-level outflow is slightly more evident over the eastern portion of the circulation, but it remains limited over that region. The current intensity estimate remains 35 kt in agreement with a Dvorak estimate from TAFB. Vertical shear is predicted to be modest over Rene during the next couple of days, and this should allow for some strengthening. The official intensity forecast is similar to the model consensus and continues to show the system becoming a hurricane, albeit briefly. After day 3, the western portion of a large upper-level trough over the eastern Atlantic is likely to impart increased shear, which should lead to weakening.

Conventional satellite and microwave fixes show a continued west-northwestward motion at about 285/11 kt. Rene is currently located on the southwest side of a mid-level ridge over the eastern Atlantic. A weakness in the ridge in the vicinity of 40W-45W longitude should induce a turn toward the northwest and north-northwest in 3-5 days. By the end of the forecast period, Rene’s forward progress begins to be blocked by building mid-level heights to its north and northwest, which should cause the cyclone’s forward motion to slow down significantly. The official track forecast has been adjusted farther to the left of the previous one, to be closer to the latest model consensus.

FORECAST POSITIONS AND MAX WINDS

INIT  09/2100Z 18.0N  32.7W   35 KT  40 MPH - Tropical Storm (WSW Cape Verde Islands)
 12H  10/0600Z 18.4N  34.3W   40 KT  45 MPH - Tropical Storm (WSW Cape Verde Islands)
 24H  10/1800Z 18.9N  36.2W   45 KT  50 MPH - Tropical Storm (WSW Cape Verde Islands)
 36H  11/0600Z 19.5N  38.1W   50 KT  60 MPH - Tropical Storm (WSW Cape Verde Islands)
 48H  11/1800Z 20.5N  40.0W   60 KT  70 MPH - Tropical Storm (WSW Cape Verde Islands)
 60H  12/0600Z 21.7N  42.0W   65 KT  75 MPH - Category 1 (WSW Cape Verde Islands)
 72H  12/1800Z 23.5N  43.8W   60 KT  70 MPH - Tropical Storm (WSW Cape Verde Islands)
 96H  13/1800Z 26.9N  46.0W   50 KT  60 MPH - Tropical Storm (ESE St, Georges, Bermuda)
120H  14/1800Z 28.5N  47.0W   40 KT  45 MPH - Tropical Storm (ESE St, Georges, Bermuda)

NWS National Hurricane Center Miami FL 1100 AM AST Wed Sep 09, 2020 

Although easterly shear has been affecting the system, Rene is producing vigorous deep convection, along with a broad convective band, over its western semicircle. Scatterometer data indicate winds to 35 knots over the northwestern quadrant, and therefore the system is again being designated as a tropical storm. The cyclone should be within an environment of moderate vertical shear, on the western side of an upper-level anticyclone, for the next couple of days. Therefore, gradual strengthening is forecast, and Rene is expected to become a hurricane late this week. By the weekend, increasing westerly shear should cause weakening. The official intensity forecast is a little above the model consensus.

Rene is currently moving west-northwestward, or 285/11 kt, on the southern side of a mid-level ridge. A weakness in the ridge near 40W longitude is likely to cause the storm to turn toward the northwest in 2 to 3 days, followed by a turn toward the north-northwest. By the end of the forecast period, Rene’s forward progress should slow as it encounters a block in the mid-level flow. As anticipated, the official track forecast is shifted to the left of the previous one, but not as far to the left as the latest corrected multi-model consensus.

FORECAST POSITIONS AND MAX WINDS

INIT  09/1500Z 17.6N  31.5W   35 KT  40 MPH - Tropical Storm (WSW Cape Verde Islands)
 12H  10/0000Z 18.1N  33.1W   40 KT  45 MPH - Tropical Storm (WSW Cape Verde Islands)
 24H  10/1200Z 18.8N  35.1W   45 KT  50 MPH - Tropical Storm (WSW Cape Verde Islands)
 36H  11/0000Z 19.5N  37.0W   50 KT  60 MPH - Tropical Storm (WSW Cape Verde Islands)
 48H  11/1200Z 20.4N  39.0W   60 KT  70 MPH - Tropical Storm (WSW Cape Verde Islands)
 60H  12/0000Z 21.7N  40.9W   65 KT  75 MPH - Category 1 (WSW Cape Verde Islands)
 72H  12/1200Z 23.5N  42.7W   60 KT  70 MPH - Tropical Storm (WSW Cape Verde Islands)
 96H  13/1200Z 27.0N  44.5W   50 KT  60 MPH - Tropical Storm (WSW Cape Verde Islands)
120H  14/1200Z 28.7N  45.0W   40 KT  45 MPH - Tropical Storm (ESE St, Georges, Bermuda)

NWS National Hurricane Center Miami FL 200 AM CVT Wed Sep 09, 2020 

Rene’s circulation remains fairly robust based on a 08/2148Z ASCAT-A overpass. However, the overall convective pattern has eroded significantly, and this is reflected in the ASCAT scatterometer wind data only showing surface winds of about 25 kt. Allowing for some undersampling, plus a recent increase in convection near the center, the intensity has only been lowered to 30 kt for this advisory. Rene remains beneath a pronounced upper-level anticyclone and outflow is fairly symmetrical in all quadrants.

The initial motion is 285/14 kt. There continues to be no significant change to previous forecast track or reasoning. Rene is expected to move generally west-northwestward around the southwestern periphery of a deep-layer ridge for the next couple of days, followed by a decrease in forward speed and a turn toward the northwest on Friday and a motion toward the north on Saturday and Sunday. The latest NHC model guidance is in decent agreement on this developing steering flow pattern, thus the new NHC track forecast is essentially just an extension of the previous advisory track and lies close to a blend of the consensus models TVCA, GFEX, and NOAA-HCCA.

Although Rene has weakened, a burst of strong convection with cloud tops colder than -80C has developed over and to the west of the center, while a fragmented band of convection has formed in the northern semicircle. These features strongly suggest that Rene is poised to restrengthen soon. Sea-surface temperatures are expected to be 26.0-26.5 deg C in the 24-60 h period, which are only marginal for strengthening to occur. However, mid-level humidity values are forecast to be near 70 percent and the cyclone is expected to remain under a favorable upper-level anticyclone during that time. Given these factors, slow but steady intensification is forecast, with Rene still expected to become a hurricane in 2-3 days. Thereafter, strong westerly to west-northwesterly vertical wind shear in excess of 25-30 kt is expected to cause Rene to weaken significantly on days 4 and 5. The new official intensity forecast is similar to but slightly lower than the previous intensity forecast, and is along the extreme upper portion of the guidance envelope and is above the intensity consensus models.

FORECAST POSITIONS AND MAX WINDS

INIT  09/0300Z 17.0N  29.3W   30 KT  35 MPH - Depression (WSW Cape Verde Islands)
 12H  09/1200Z 17.5N  31.1W   35 KT  40 MPH - Tropical Storm (WSW Cape Verde Islands)
 24H  10/0000Z 18.4N  33.7W   40 KT  45 MPH - Tropical Storm (WSW Cape Verde Islands)
 36H  10/1200Z 19.3N  35.9W   50 KT  60 MPH - Tropical Storm (WSW Cape Verde Islands)
 48H  11/0000Z 20.5N  38.1W   60 KT  70 MPH - Tropical Storm (WSW Cape Verde Islands)
 60H  11/1200Z 22.1N  39.8W   65 KT  75 MPH - Category 1 (WSW Cape Verde Islands)
 72H  12/0000Z 24.2N  41.4W   60 KT  70 MPH - Tropical Storm (WSW Cape Verde Islands)
 96H  13/0000Z 28.5N  42.6W   50 KT  60 MPH - Tropical Storm (WSW Cape Verde Islands)
120H  14/0000Z 30.2N  40.3W   40 KT  45 MPH - Tropical Storm (WSW Cape Verde Islands)

NWS National Hurricane Center Miami FL 800 PM CVT Tue Sep 08, 2020 (

Rene has not changed much throughout the day. The storm is producing deep convection that is loosely organized in bands around the center. The satellite intensity estimates are unchanged from earlier and range from 25 kt to 40 kt. Based on these data and the earlier ASCAT pass, the initial intensity is again held at 35 kt. The eastern-most bands of Rene are now pulling west of the Cabo Verde Islands, and the Tropical Storm Warning for those islands has been discontinued.

Although Rene has struggled to maintain its intensity during the past 24 hours, the models insist that the cyclone will begin to take advantage of the generally conducive conditions of low wind shear, high moisture, and relatively warm waters. Therefore, the NHC intensity forecast continues to show Rene strengthening to a hurricane in a couple of days. Beyond that time, however, Rene will likely be moving into an environment of strong westerly wind shear, which should cause the storm to weaken in the 3-5 day time period. This forecast is largely an update of the previous one and closely follows the IVCN model.

The tropical storm continues to move westward at 14 kt. There has been no significant change to the track forecast reasoning. A mid-level ridge should continue to steer Rene westward to west-northwestward for the next couple of days. After that time, the storm should slow down and gradually turn to the north and then to the northeast as it moves into a weakness in the ridge. There is a little less spread in the guidance this cycle, but there remain differences in the models concerning where and how sharply Rene recurves. The NHC track forecast is similar to the previous one and lies close to the TVCA and TVCX consensus models.

FORECAST POSITIONS AND MAX WINDS

INIT  08/2100Z 16.8N  27.9W   35 KT  40 MPH - Tropical Storm (WSW Cape Verde Islands)
 12H  09/0600Z 17.2N  29.6W   40 KT  45 MPH - Tropical Storm (WSW Cape Verde Islands)
 24H  09/1800Z 18.0N  32.2W   50 KT  60 MPH - Tropical Storm (WSW Cape Verde Islands)
 36H  10/0600Z 18.9N  34.8W   60 KT  70 MPH - Tropical Storm (WSW Cape Verde Islands)
 48H  10/1800Z 19.9N  37.0W   65 KT  75 MPH - Category 1 (WSW Cape Verde Islands)
 60H  11/0600Z 21.3N  38.8W   70 KT  80 MPH - Category 1 (WSW Cape Verde Islands)
 72H  11/1800Z 23.2N  40.3W   65 KT  75 MPH - Category 1 (WSW Cape Verde Islands)
 96H  12/1800Z 27.7N  42.2W   55 KT  65 MPH - Tropical Storm (WSW Cape Verde Islands)
120H  13/1800Z 30.5N  40.5W   50 KT  60 MPH - Tropical Storm (WSW Cape Verde Islands)

NWS National Hurricane Center Miami FL 200 PM CVT Tue Sep 08, 2020 

Rene is starting to pull away from the Cabo Verde Islands, though some of the outer rainbands are affecting the far northwestern islands. Although the tropical storm has a well-defined circulation, the convective banding features have not become any better organized since yesterday. The satellite classifications are largely unchanged and range from 25 to 37 kt, and a recent ASCAT-B pass showed maximum winds in the 30-35 kt range. Based on all of this data, the initial intensity is again held at 35 kt.

The tropical storm is moving westward at a faster pace of 14 kt. A mid-level ridge to the north of Rene is expected to build westward, which should cause the cyclone to move westward to west-northwestward at about the same forward speed during the next couple of days. After that time, the storm is expected to slow down and turn northwestward and then northward as it moves into a pronounced weakness in the ridge. Although the models agree on the overall scenario, there are notable differences in where and how sharply Rene will recurve with the GFS on the right side of the guidance and the ECMWF on the left. The NHC track forecast is adjusted a little to the right of the previous one, but still lies closer to the left side of the guidance envelope between the HCCA and TVCA consensus aids.

Although Rene has not strengthened since yesterday, the models continue to suggest that the storm will steadily strengthen during the next few days while it moves over relatively warm 26-27 C waters and remains in environment of low wind shear and high moisture. Beyond that time, increasing southwesterly wind shear and drier air should end the strengthening trend and induce gradual weakening. The NHC intensity forecast is largely an update of the previous one and lies near the HCCA and IVCN models.

Key Messages:

  • 1. Rene is expected to produce tropical storm conditions across portions of the western Cabo Verde Islands for a few more hours. A Tropical Storm Warning remains in effect for those islands.
  • 2. Rene will continue to bring locally heavy rainfall to portions of the western Cabo Verde Islands today.
FORECAST POSITIONS AND MAX WINDS

INIT  08/1500Z 16.5N  26.5W   35 KT  40 MPH - Tropical Storm (WSW Cape Verde Islands)
 12H  09/0000Z 16.8N  28.5W   35 KT  40 MPH - Tropical Storm (WSW Cape Verde Islands)
 24H  09/1200Z 17.4N  31.1W   45 KT  50 MPH - Tropical Storm (WSW Cape Verde Islands)
 36H  10/0000Z 18.3N  33.7W   55 KT  65 MPH - Tropical Storm (WSW Cape Verde Islands)
 48H  10/1200Z 19.3N  36.2W   65 KT  75 MPH - Category 1 (WSW Cape Verde Islands)
 60H  11/0000Z 20.5N  38.2W   70 KT  80 MPH - Category 1 (WSW Cape Verde Islands)
 72H  11/1200Z 22.1N  39.8W   70 KT  80 MPH - Category 1 (WSW Cape Verde Islands)
 96H  12/1200Z 26.5N  42.2W   60 KT  70 MPH - Tropical Storm (WSW Cape Verde Islands)
120H  13/1200Z 29.7N  42.0W   50 KT  60 MPH - Tropical Storm (WSW Cape Verde Islands)

NWS National Hurricane Center Miami FL 200 AM CVT Tue Sep 08, 2020 

Convection has noticeably waned during the past few hours as Rene’s center moved directly over Boa Vista island between 07/2200 UTC and 08/0000 UTC. The highest observed wind speed thus far has been a 10-minute average wind of 25 kt at Sal/GVAC. Satellite intensity estimates range from 35 kt from TAFB to 30 kt from SAB. A 07/2323 UTC ASCAT-B overpass indicated peak winds of 27 kt, but land obscuration likely has resulted in some missed higher wind speeds. For now, the intensity will remain at 35 kt.

The initial motion is 280/12 kt. A westward motion is expected today, followed by a west-northwestward motion through Thursday as Rene rounds the southwestern periphery of a deep-layer subtropical ridge. On days 4 ad 5, the cyclone is forecast to move more slowly northwestward to north-northwestward through a weakness in the aforementioned ridge. The track guidance appears to have stabilized on the latest set of model runs and, thus, the new NHC forecast track is very similar to the previous advisory track, and lies close to a blend of the TVCA and NOAA-HCCA consensus track models.

The intensity forecast was held steady for the next 12 h or so until Rene clears the negative influence of the mountainous Cabo Verde Islands. It’s possible that Rene could even weaken by the time it passes the western Cabo Verde Islands. Thereafter, however, environmental conditions appear conducive for the cyclone to gradually strengthen, becoming a hurricane on day 3. By days 4 and 5, an increase in southwesterly vertical wind shear is expected to induce a weakening trend. The new NHC intensity forecast is similar to a blend of the IVCN and the HCCA intensity consensus models, and the GFS model.

Key Messages:

  • 1. Rene is expected to produce tropical storm conditions across portions of the Cabo Verde Islands this morning and afternoon. A Tropical Storm Warning is in effect for those islands.
  • 2. Rene will bring locally heavy rainfall to portions of the Cabo Verde Islands through this afternoon.
FORECAST POSITIONS AND MAX WINDS

INIT  08/0300Z 16.2N  23.5W   35 KT  40 MPH - Tropical Storm (WSW Cape Verde Islands)
 12H  08/1200Z 16.5N  25.5W   35 KT  40 MPH - Tropical Storm (WSW Cape Verde Islands)
 24H  09/0000Z 16.8N  28.2W   45 KT  50 MPH - Tropical Storm (WSW Cape Verde Islands)
 36H  09/1200Z 17.3N  30.9W   50 KT  60 MPH - Tropical Storm (WSW Cape Verde Islands)
 48H  10/0000Z 18.2N  33.6W   60 KT  70 MPH - Tropical Storm (WSW Cape Verde Islands)
 60H  10/1200Z 19.1N  36.1W   65 KT  75 MPH - Category 1 (WSW Cape Verde Islands)
 72H  11/0000Z 20.2N  38.3W   70 KT  80 MPH - Category 1 (WSW Cape Verde Islands)
 96H  12/0000Z 23.1N  41.9W   65 KT  75 MPH - Category 1 (WSW Cape Verde Islands)
120H  13/0000Z 27.6N  44.1W   55 KT  65 MPH - Tropical Storm (WSW Cape Verde Islands)

NWS National Hurricane Center Miami FL 800 PM CVT Mon Sep 07, 2020 

The cyclone is getting better organized on its approach  to the Cabo Verde Islands. Banding features are now well established over the western part of the circulation, and some smaller bands are filling in east of the center. The satellite intensity estimates currently range from 30 to 35 kt. Based on this data and the improved satellite appearance of the system, the initial intensity is raised to 35 kt, making the cyclone Tropical Storm Rene. Rene is the 17th named storm of the 2020 Atlantic hurricane season. It is also the earliest 17th named storm of any Atlantic season by 11 days. The previous record was Rita, which formed on September 18, 2005.

Rene is moving west-northwestward at 10 kt, and it should continue moving in that direction with some increase in forward speed for at least the next few days while subtropical ridging builds westward to the north of the storm. Toward the end of the forecast period, a turn to the northwest is expected as Rene moves into a weakness in the ridge. The models have shifted eastward at the longer ranges, especially the ECMWF model, and the NHC forecast has been adjusted in that direction at days 3 through 5.

Rene is forecast to gradually strengthen during the next few days as the storm is expected to remain over relatively warm water while moving through an environment consisting of low vertical wind shear and high amounts of moisture. An increase in southwesterly shear late this week and this weekend should end the strengthening trend and induce some weakening. The NHC intensity forecast is again an update of the previous one, and is now in line with the HCCA and IVCN consensus models.

Key Messages:

  • 1. Rene is expected to produce tropical storm conditions across portions of the Cabo Verde Islands tonight and early Tuesday. A Tropical Storm Warning is in effect for those islands.
  • 2. Rene will bring locally heavy rainfall to portions of the Cabo Verde Islands through Tuesday morning.
FORECAST POSITIONS AND MAX WINDS

INIT  07/2100Z 16.1N  22.3W   35 KT  40 MPH - Tropical Storm (WSW Cape Verde Islands)
 12H  08/0600Z 16.3N  24.1W   40 KT  45 MPH - Tropical Storm (WSW Cape Verde Islands)
 24H  08/1800Z 16.7N  26.8W   50 KT  60 MPH - Tropical Storm (WSW Cape Verde Islands)
 36H  09/0600Z 17.2N  29.6W   55 KT  65 MPH - Tropical Storm (WSW Cape Verde Islands)
 48H  09/1800Z 17.8N  32.3W   60 KT  70 MPH - Tropical Storm (WSW Cape Verde Islands)
 60H  10/0600Z 18.6N  35.0W   65 KT  75 MPH - Category 1 (WSW Cape Verde Islands)
 72H  10/1800Z 19.6N  37.4W   70 KT  80 MPH - Category 1 (WSW Cape Verde Islands)
 96H  11/1800Z 22.1N  41.3W   70 KT  80 MPH - Category 1 (WSW Cape Verde Islands)
120H  12/1800Z 26.0N  44.0W   65 KT  75 MPH - Category 1 (WSW Cape Verde Islands)

NWS National Hurricane Center Miami FL 200 PM CVT Mon Sep 07, 2020 

Tropical Depression Eighteen is very near tropical storm strength. Satellite images show banding features gradually organizing on the west side of the circulation. An ASCAT-B overpass showed maximum winds around or slightly above 30 kt in the bands to the northwest of the center. The Dvorak classifications from TAFB and SAB are lower, however. The initial intensity is held at 30 kt for now, but it seems very likely that the depression will become a tropical storm later today.

The cyclone is moving west-northwestward at 9 kt. A subtropical ridge situated to the north of the system is expected to build westward across the eastern Atlantic during the next 3 or 4 days. This steering pattern should keep the system on a general west-northwestward course during that time. By the weekend, the depression will likely be moving into a weakness in the ridge, which should cause a turn to the northwest. The models are in good agreement during the next few days, but there is increasing spread in the guidance by the end of the forecast period. The NHC forecast is very similar to the previous one and lies near the various consensus models.

The depression will likely strengthen during the next few days as it remains in conducive environmental conditions of low wind shear, relatively warm waters, and a moist airmass. There will likely be an increase in shear by the end of the week and this weekend, which should end the strengthening trend and perhaps induce some weakening at that time. The NHC intensity forecast is largely an update of the previous one, and lies near the high end of the model guidance.

Key Messages:

  • 1. The depression is forecast to strengthen into a tropical storm later today and tropical storm conditions are expected to spread over portions of the Cabo Verde Islands later today and tonight. A Tropical Storm Warning is in effect for those islands.
  • 2. The depression is expected to bring locally heavy rainfall to portions of the Cabo Verde Islands through Tuesday morning.
FORECAST POSITIONS AND MAX WINDS

INIT  07/1500Z 15.7N  21.2W   30 KT  35 MPH - Depression (WSW Cape Verde Islands)
 12H  08/0000Z 16.1N  23.1W   35 KT  40 MPH - Tropical Storm (WSW Cape Verde Islands)
 24H  08/1200Z 16.5N  25.8W   45 KT  50 MPH - Tropical Storm (WSW Cape Verde Islands)
 36H  09/0000Z 16.9N  28.6W   50 KT  60 MPH - Tropical Storm (WSW Cape Verde Islands)
 48H  09/1200Z 17.4N  31.5W   55 KT  65 MPH - Tropical Storm (WSW Cape Verde Islands)
 60H  10/0000Z 18.0N  34.1W   60 KT  70 MPH - Tropical Storm (WSW Cape Verde Islands)
 72H  10/1200Z 18.6N  36.5W   65 KT  75 MPH - Category 1 (WSW Cape Verde Islands)
 96H  11/1200Z 20.6N  40.6W   70 KT  80 MPH - Category 1 (WSW Cape Verde Islands)
120H  12/1200Z 23.2N  43.8W   65 KT  75 MPH - Category 1 (WSW Cape Verde Islands)

NWS National Hurricane Center Miami FL 800 PM EDT Wed Sep 2, 2020

For the North Atlantic…Caribbean Sea and the Gulf of Mexico:

The National Hurricane Center is issuing advisories on Tropical Depression Omar, located a few hundred miles north of Bermuda, and on Tropical Storm Nana, located about 150 miles east of Belize City, Belize.

  • 1. An area of low pressure located about midway between the Windward Islands and west Africa is producing a small area of showers and thunderstorms. Some development of this system is possible this week as it drifts generally westward over the eastern and central tropical Atlantic Ocean. * Formation chance through 48 hours…low…20 percent. * Formation chance through 5 days…low...30 percent. [Rene]
  • 2. A tropical wave, located just off the coast of west Africa, is producing disorganized shower and thunderstorm activity. The wave is expected to merge with a disturbance centered a couple of hundred miles southeast of the Cabo Verde Islands toward the end of the week. Gradual development of this system is then possible, and a tropical depression could form over the weekend or early next week while it moves westward over the eastern and central tropical Atlantic Ocean. * Formation chance through 48 hours…low…20 percent. * Formation chance through 5 days…medium...60 percent. [Paulette]

NWS National Hurricane Center Miami FL 800 AM EDT Wed Sep 2 2020

For the North Atlantic…Caribbean Sea and the Gulf of Mexico:

The National Hurricane Center is issuing advisories on Tropical Storm Omar, located a few hundred miles northwest of Bermuda, and on Tropical Storm Nana, located a couple hundred miles northeast of the coast of Honduras.

  • 1. Showers and thunderstorms associated with an area of low pressure located about midway between the Windward Islands and west Africa remain disorganized. Some development of this system, however, is possible this week as it meanders over the eastern and central tropical Atlantic Ocean. * Formation chance through 48 hours…low…20 percent. * Formation chance through 5 days…low…30 percent. [Rene]
  • 2. Surface observations and satellite derived data indicate that a tropical wave has emerged off the coast of Africa. The wave is expected to merge with a disturbance centered a couple of hundred miles southeast of the Cabo Verde Islands in the next day or so. Gradual development of this system is then possible, and a tropical depression could form by this weekend while it moves westward over the eastern and central tropical Atlantic Ocean. * Formation chance through 48 hours…low…10 percent. * Formation chance through 5 days…medium...60 percent. [Paulette]

NWS National Hurricane Center Miami FL 800 PM EDT Tue Sep 1, 2020

For the North Atlantic…Caribbean Sea and the Gulf of Mexico:

The National Hurricane Center is issuing advisories on Tropical Storm Omar, located a couple of hundred miles east of Cape Hatteras, North Carolina, and on Tropical Storm Nana, located about 150 miles southwest of Jamaica.

  • 1. Showers and thunderstorms associated with a small area of low pressure about midway between the Windward Islands and west Africa appear to be slowly becoming better organized. Some additional development of this system is possible this week as the system meanders in the central tropical Atlantic Ocean. * Formation chance through 48 hours…low…20 percent. * Formation chance through 5 days…low…30 percent.
  • 2. A tropical wave is expected to emerge off the coast of Africa on Wednesday and merge with a disturbance centered a couple of hundred miles southeast of the Cabo Verde Islands in the next day or so. Gradual development of this system is then possible, and this system could become a tropical depression by this weekend while it moves slowly westward over the eastern tropical Atlantic Ocean. * Formation chance through 48 hours…low…10 percent. * Formation chance through 5 days…medium…60 percent. [Paulette]

NWS Weather Prediction Center College Park MD 200 PM EDT Tue Sep 1, 2020

For the North Atlantic…Caribbean Sea and the Gulf of Mexico:

The National Hurricane Center is issuing advisories on Tropical Depression Fifteen, located a couple of hundred miles offshore of North Carolina, and on newly formed Tropical Storm Nana, located about 100 miles south of Jamaica.

  • 1. A small area of low pressure has formed about midway between the Windward Islands and west Africa. Upper-level winds are marginally conducive for some slow development this week as the system meanders in the central tropical Atlantic Ocean. * Formation chance through 48 hours…low…10 percent. * Formation chance through 5 days…low…20 percent. [Rene]
  • 2. A tropical wave is expected to emerge off the coast of Africa in about a day and merge with a disturbance centered about 200 miles southeast of the Cabo Verde Islands in a couple of days. Gradual development of this system is then possible, and this system could become a tropical depression by this weekend while it moves slowly westward over the eastern tropical Atlantic Ocean. * Formation chance through 48 hours…low…near 0 percent. * Formation chance through 5 days…medium…50 percent.  [Paulette]

NWS Weather Prediction Center College Park MD 200 PM EDT Tue Sep 1, 2020

For the North Atlantic…Caribbean Sea and the Gulf of Mexico:

The National Hurricane Center is issuing advisories on Tropical Depression Fifteen, located a couple of hundred miles offshore of North Carolina, and on newly formed Tropical Storm Nana, located about 100 miles south of Jamaica.

  • 1. A small area of low pressure has formed about midway between the Windward Islands and west Africa. Upper-level winds are marginally conducive for some slow development this week as the system meanders in the central tropical Atlantic Ocean. * Formation chance through 48 hours…low…10 percent. * Formation chance through 5 days…low…20 percent. [Rene]
  • 2. A tropical wave is expected to emerge off the coast of Africa in about a day and merge with a disturbance centered about 200 miles southeast of the Cabo Verde Islands in a couple of days. Gradual development of this system is then possible, and this system could become a tropical depression by this weekend while it moves slowly westward over the eastern tropical Atlantic Ocean. * Formation chance through 48 hours…low…near 0 percent. * Formation chance through 5 days…medium…50 percent. [Paulette]

If this system is named, it will become Tropical Storm Rene.

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