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Tropical Storm FRED Forecast Discussion Number 3

2015-08-30 16:50:26| National Hurricane Center (Atlantic)

Issued at 1100 AM AST SUN AUG 30 2015 000 WTNT41 KNHC 301450 TCDAT1 TROPICAL STORM FRED DISCUSSION NUMBER 3 NWS NATIONAL HURRICANE CENTER MIAMI FL AL062015 1100 AM AST SUN AUG 30 2015 Visible satellite imagery indicates that convection associated with the tropical cyclone continues to organize. A curved band of convection now wraps almost completely around the center and recent images show that a small CDO feature has developed. An earlier WindSat microwave overpass also revealed a well-defined inner core. Dvorak T-numbers from TAFB and UW/CIMSS are around 3.0, and based on these the initial intensity is raised to 45 kt. The environment ahead of Fred appears conducive for strengthening during the next 24 to 36 hours. During that time, there will be sufficient mid-level moisture, the shear is expected to remain low, and the cyclone will be traversing sea surface temperatures of 27 to 28C. Therefore, steady strengthening is anticipated and the SHIPS and LGEM models bring Fred to hurricane status within 24 hours. Strengthening is also supported by the GFS and ECMWF models, which both show the cyclone deepening while it moves through the Cape Verde Islands. After 36 hours, lower sea surface temperatures, increasing southwesterly shear, and a more stable environment should cause weakening. Fred is moving northwestward at about 11 kt. The tropical storm is forecast to move northwestward toward a break in the subtropical ridge to the north of the Cape Verde Islands. In a couple of days, the ridge is forecast to build westward, which should cause Fred to turn west-northwestward. As Fred weakens and become a more shallow cyclone late in the period, a westward to west-northwestward motion is expected. The NHC track is near the consensus of the ECMWF and GFS models through 72 hours. Later in the period, the NHC forecast shows a weaker system moving more westward, and this track is along the southern edge of the guidance in best agreement with the ECMWF. Based on this track and intensity forecast, the Meteorological Service of the Cape Verde Islands has issued a Hurricane Warning for those islands. Please note that the track/cone graphic, an automatically generated product, does not have the capability of displaying warnings for the Cape Verde Islands. FORECAST POSITIONS AND MAX WINDS INIT 30/1500Z 13.4N 19.9W 45 KT 50 MPH 12H 31/0000Z 14.3N 21.3W 55 KT 65 MPH 24H 31/1200Z 15.7N 23.1W 65 KT 75 MPH 36H 01/0000Z 17.2N 25.1W 65 KT 75 MPH 48H 01/1200Z 18.3N 27.1W 65 KT 75 MPH 72H 02/1200Z 19.5N 31.5W 55 KT 65 MPH 96H 03/1200Z 20.5N 35.5W 45 KT 50 MPH 120H 04/1200Z 21.0N 39.5W 40 KT 45 MPH $$ Forecaster Brown

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Hurricane JIMENA Forecast Discussion Number 16

2015-08-30 16:41:54| National Hurricane Center (East Pacific)

Issued at 800 AM PDT SUN AUG 30 2015 000 WTPZ43 KNHC 301441 TCDEP3 HURRICANE JIMENA DISCUSSION NUMBER 16 NWS NATIONAL HURRICANE CENTER MIAMI FL EP132015 800 AM PDT SUN AUG 30 2015 Infrared satellite images and a recent GCOM microwave pass indicate that there is still some evidence of a double eyewall structure. The southern portion of Jimena's inner eyewall has eroded a little during the past few hours, causing a slightly asymmetric presentation. The initial wind speed is maintained at 115 kt, based on a blend of the satellite intensity estimates from TAFB, SAB, and ADT values from CIMSS at the University of Wisconsin, though it is possible that Jimena could be a little less intense. The atmospheric environment is expected to remain conducive for Jimena to remain a strong cyclone for the next several days as the SHIPS model shows the wind shear remaining less than 10 kt. The only negative environmental factor is cooler water with lower oceanic heat content along the expected track. Most of the guidance shows a slow decay of the hurricane during the next several days, and the NHC intensity forecast follows that theme. This forecast is in best agreement with the SHIPS model. Jimena is moving west-northwestward at about 12 kt steered by a subtropical ridge to its north and northeast. This general motion is expected to persist for another day or two. After that time, the hurricane is expected to decelerate in response to weakening steering currents caused by an amplifying trough extending southwestward from the western United States. The new track forecast is adjusted a little to the right of the previous one to come in better agreement with the latest runs of the GFS and ECMWF models. FORECAST POSITIONS AND MAX WINDS INIT 30/1500Z 14.2N 129.6W 115 KT 130 MPH 12H 31/0000Z 14.9N 131.6W 110 KT 125 MPH 24H 31/1200Z 15.6N 134.2W 110 KT 125 MPH 36H 01/0000Z 16.2N 136.4W 105 KT 120 MPH 48H 01/1200Z 16.8N 138.2W 100 KT 115 MPH 72H 02/1200Z 17.7N 140.6W 95 KT 110 MPH 96H 03/1200Z 18.5N 142.3W 85 KT 100 MPH 120H 04/1200Z 19.2N 143.4W 75 KT 85 MPH $$ Forecaster Cangialosi

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Hurricane JIMENA Forecast Discussion Number 15

2015-08-30 10:49:05| National Hurricane Center (East Pacific)

Issued at 200 AM PDT SUN AUG 30 2015 000 WTPZ43 KNHC 300848 TCDEP3 HURRICANE JIMENA DISCUSSION NUMBER 15 NWS NATIONAL HURRICANE CENTER MIAMI FL EP132015 200 AM PDT SUN AUG 30 2015 The overall cloud pattern has degraded a little during the past few hours with some cooling of the eye of Jimena. Microwave data confirm the ongoing eyewall replacement, with some evidence that the inner eyewall is eroding at the expense of an outer eyewall. Satellite estimates have come down somewhat, so the initial intensity is reduced to 115 kt. The intensity forecast for the next day or so is primarily dependent on when and if the eyewall cycle completes. After considering the low-shear, warm-water environment, I will assume that Jimena will be able to complete the eyewall cycle and not lose much more intensity this weekend. After that time, overall environmental conditions only gradually become less conducive. These factors suggest a slow decay of the cyclone then, although there is considerable uncertainty since the intensity guidance is rather divergent by long range. There has not been any significant change to the intensity consensus and, given the uncertainties, the new forecast is kept nearly the same as the old one. The initial motion estimate is 290/11. So far Jimena has been a well-behaved cyclone as the subtropical ridge has provided a steady steering current. This ridge is forecast to remain firm for the next few days, keeping the west-northwestward motion in place. Around the time Jimena reaches the central Pacific, it should slow down considerably due to a weakening of the subtropical ridge, which could allow a turn to the northwest by the end of the period. However, the bulk of guidance keep the hurricane moving slowly west-northwestward through day 5, with some outliers. No significant changes were made to the latest NHC prediction since the model consensus is very close to the previous official forecast. FORECAST POSITIONS AND MAX WINDS INIT 30/0900Z 13.7N 128.4W 115 KT 130 MPH 12H 30/1800Z 14.3N 130.1W 115 KT 130 MPH 24H 31/0600Z 15.1N 132.7W 115 KT 130 MPH 36H 31/1800Z 15.8N 135.2W 110 KT 125 MPH 48H 01/0600Z 16.3N 137.3W 105 KT 120 MPH 72H 02/0600Z 17.2N 140.2W 95 KT 110 MPH 96H 03/0600Z 17.9N 142.0W 85 KT 100 MPH 120H 04/0600Z 18.5N 143.5W 75 KT 85 MPH $$ Forecaster Blake

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Tropical Storm FRED Forecast Discussion Number 2

2015-08-30 10:47:31| National Hurricane Center (Atlantic)

Issued at 500 AM AST SUN AUG 30 2015 000 WTNT41 KNHC 300847 TCDAT1 TROPICAL STORM FRED DISCUSSION NUMBER 2 NWS NATIONAL HURRICANE CENTER MIAMI FL AL062015 500 AM AST SUN AUG 30 2015 The convective cloud pattern of the tropical cyclone has continued to improve this early morning with the development of a small CDO feature and a tightly curved band in the western and southern quadrants. A 0542 UTC SSMI/S microwave satellite image further indicated that the convective band wraps almost completely around a primitive mid-level eye feature. The initial intensity is raised to 35 kt based on a Dvorak classification of T2.5/35 kt from TAFB, and this intensity could be conservative based on the impressive SSMI/S satellite signature. This makes Fred only the fourth Atlantic tropical storm to form east of 19W longitude in NHC's database. The initial motion remains 305/10 kt. There is no change to the previous forecast track reasoning. Fred is expected to move northwestward toward a weakness just northwest of the Cape Verde Islands within a deep-layer subtropical ridge. The mid-tropospheric trough that is responsible for the weakness is forecast by the global and regional models to shift eastward over the next 24-36 hours, which should allow the ridge to build back in, forcing Fred on a west-northwestward to westward track after 48-72 hours. The latest NHC model guidance is tightly packed about the previous forecast track, so the new track forecast is essentially just an update of the previous advisory, and lies close to the GFEX and TVCA consensus model solutions. Fred is expected to remain in favorable environmental and oceanic conditions for the next 36 hours, characterized by vertical wind shear less than 10 kt, mid-level humidity values greater than 70 percent, and sea-surface temperatures of 27.5-28 deg C. The main inhibiting factor is decreasing instability ahead of the cyclone after 24 hours. However, there should still be enough available instability to support deep convection that will allow at least steady strengthening through 36 hours to occur, and Fred could still reach hurricane status before or while it moves through the Cape Verde Islands in 36 hours or so. After 48 hours, southwesterly vertical wind shear is expected to begin affecting the cyclone while Fred is moving over sub-27C SSTs. These less favorable conditions should combine to induce a gradual weakening trend. The NHC intensity forecast is similar to the previous advisory and the IVCN intensity consensus model. FORECAST POSITIONS AND MAX WINDS INIT 30/0900Z 12.4N 18.9W 35 KT 40 MPH 12H 30/1800Z 13.4N 20.3W 45 KT 50 MPH 24H 31/0600Z 14.6N 22.1W 55 KT 65 MPH 36H 31/1800Z 16.0N 23.9W 60 KT 70 MPH 48H 01/0600Z 17.0N 25.8W 60 KT 70 MPH 72H 02/0600Z 18.5N 29.9W 60 KT 70 MPH 96H 03/0600Z 19.2N 34.0W 55 KT 65 MPH 120H 04/0600Z 19.8N 38.8W 50 KT 60 MPH $$ Forecaster Stewart

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Tropical Depression SIX Forecast Discussion Number 1

2015-08-30 07:49:19| National Hurricane Center (Atlantic)

Issued at 130 AM AST SUN AUG 30 2015 000 WTNT41 KNHC 300549 TCDAT1 TROPICAL DEPRESSION SIX SPECIAL DISCUSSION NUMBER 1 NWS NATIONAL HURRICANE CENTER MIAMI FL AL062015 130 AM AST SUN AUG 30 2015 The well-defined low pressure system located to the west of Conakry, Guinea, has acquired sufficient organized convection to be classified as a tropical depression. The initial intensity of 30 kt is based on a Dvorak satellite intensity estimate of T2.0/30 kt from TAFB and two earlier ASCAT scatterometer passes indicating at least 30 kt in the southern semicircle. The initial motion estimate is 305/10 kt. The depression is located south of a deep-layer subtropical ridge that extends westward across northwestern Africa and into the eastern Atlantic for several hundred miles. However, a weakness is located in a portion of the ridge to the north of the Cape Verde Islands due to a pronounced mid-latitude trough noted in water vapor imagery digging east-southeastward. This should allow the cyclone to move northwestward toward the Cape Verde Islands through 48 hours. After that time, the NHC model guidance is in fair agreement on the aforementioned trough lifting out, allowing the ridge to build back in, which is expected to force the cyclone on a more westward track. The NHC track forecast lies close to the consensus models TVCA and GFEX. The depression is embedded within favorable environmental and oceanic conditions consisting of low vertical wind shear of less than 10 kt, a moist mid-troposphere, and sea-surface temperatures greater than 28 deg C, which should allow for steady strengthening for the next 48 hours or so. The main inhibiting factor is the decreasing instability ahead of the cyclone after 24-36 hours. However, the possibility still exists for the system to reach hurricane status before or while it moves through the Cape Verde Islands in 36-48 hours. For this reason, the Meteorological Service of the Cape Verde Islands has issued a Hurricane Watch and a Tropical Storm Warning for all of the Cape Verdes. The official intensity forecast is basically a blend of the SHIPS and LGEM models. FORECAST POSITIONS AND MAX WINDS INIT 30/0530Z 12.1N 18.4W 30 KT 35 MPH 12H 30/1200Z 12.7N 19.5W 35 KT 40 MPH 24H 31/0000Z 13.9N 21.2W 45 KT 50 MPH 36H 31/1200Z 15.3N 23.1W 55 KT 65 MPH 48H 01/0000Z 16.6N 24.9W 60 KT 70 MPH 72H 02/0000Z 18.3N 29.0W 60 KT 70 MPH 96H 03/0000Z 18.9N 32.9W 55 KT 65 MPH 120H 04/0000Z 19.3N 36.8W 50 KT 60 MPH $$ Forecaster Stewart

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