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Tropical Depression TEN-E Forecast Discussion Number 1

2014-08-04 04:47:32| National Hurricane Center (East Pacific)

Issued at 800 PM PDT SUN AUG 03 2014 000 WTPZ45 KNHC 040247 TCDEP5 TROPICAL DEPRESSION TEN-E DISCUSSION NUMBER 1 NWS NATIONAL HURRICANE CENTER MIAMI FL EP102014 800 PM PDT SUN AUG 03 2014 Showers and thunderstorms associated with an area of low pressure several hundred miles southwest of Manzanillo, Mexico, have become more concentrated this afternoon and evening. The deep convection has also become better organized, taking on the form of a band with increasing curvature over the western half of the circulation. Dvorak intensity estimates are at T2.0/30 kt and T2.5/35 kt from SAB and TAFB, respectively. Based on these data, advisories are being initiated at this time, and the initial intensity of the depression is set at 30 kt. Some scatter in center fixes over the last 24 hours has made the initial motion more uncertain than normal, but an estimate of 270/09 seems reasonable. The depression is situated to the south of a subtropical ridge extending west-southwestward from western Mexico that should cause the depression to move westward or perhaps even west-southwestward during the next day or two at a faster forward speed. Later in the forecast period, the cyclone will become caught under the eastern end of a subtropical ridge forming over the central Pacific, with an orientation of the ridge such that a west-northwestward heading should commence. This first NHC track forecast is close to the multi-model consensus TVCE and near but slightly south of the ECMWF/GFS solutions. Persistent moderate northeasterly shear has been affecting the system for a couple of days now, and according to SHIPS model output only a marginal decrease in this shear is likely during the next 3 days. Still the cyclone will be over warm waters and encountering an environment of higher moisture, so steady intensification is expected. Although sea surface temperatures will be gradually decreasing after day 3, the shear should nearly diminish and thermodynamic factors are expected to still be favorable enough to allow for some additional strengthening or in the very least a steady state cyclone. One caveat to intensity forecast late in the period could be the effect of the cold wake left behind by Hurricane Iselle. The intensity forecast is close to the multi-model consensus IVCN throughout the forecast period. FORECAST POSITIONS AND MAX WINDS INIT 04/0300Z 13.5N 116.9W 30 KT 35 MPH 12H 04/1200Z 13.3N 118.7W 35 KT 40 MPH 24H 05/0000Z 13.1N 121.1W 40 KT 45 MPH 36H 05/1200Z 13.0N 123.6W 50 KT 60 MPH 48H 06/0000Z 13.1N 126.2W 60 KT 70 MPH 72H 07/0000Z 13.8N 131.0W 70 KT 80 MPH 96H 08/0000Z 14.5N 136.2W 75 KT 85 MPH 120H 09/0000Z 15.0N 142.0W 75 KT 85 MPH $$ Forecaster Kimberlain

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Tropical Storm BERTHA Forecast Discussion Number 13

2014-08-04 04:45:28| National Hurricane Center (Atlantic)

Issued at 1100 PM EDT SUN AUG 03 2014 000 WTNT43 KNHC 040245 TCDAT3 TROPICAL STORM BERTHA DISCUSSION NUMBER 13 NWS NATIONAL HURRICANE CENTER MIAMI FL AL032014 1100 PM EDT SUN AUG 03 2014 Recent satellite and aircraft reconnaissance data indicate that the circulation of Bertha has become much better defined this evening. The tropical cyclone has also quickly strengthened as convection has increased and become organized in a band around the eastern portion of the circulation. An Air Force reconnaissance aircraft has measured peak believable SFMR winds of around 55 kt. Although the flight-level winds would support a little lower initial intensity, a recent dropsonde measured winds in the lowest 150 meters that also supports an initial wind speed of 55 kt. The aircraft data also indicate that the minimum pressure has fallen to around 1007 mb. The strong northwesterly vertical wind shear that has been affecting Bertha is forecast to decrease further during the next 24 hours. This should allow for additional strengthening, and the updated NHC intensity forecast calls for Bertha to become a hurricane in a day or so. In 36 to 48 hours, strong west-southwesterly upper-level winds are forecast to cause a significant increase in vertical shear. The shear, along with decreasing sea surface temperatures, should cause some weakening before Bertha becomes an extratropical low over the North Atlantic in three to four days. Bertha is moving north-northwest at 15 kt. The cyclone should turn northward and then north-northeastward during the next day or so while it moves between a subtropical high to its east and a mid- to upper-level trough over the eastern United States. In a couple of days, Bertha is expected to accelerate northeastward and then turn east-northeastward when it moves into the mid-latitude westerlies. The model guidance is generally in good agreement on this scenario through 72 hours, and the new NHC track forecast is similar to the previous advisory during that time. There is increasing spread in the track guidance after three days with the ECMWF and UKMET models predicting a much faster motion over the North Atlantic than the latest GFS. The four- and five-day forecast positions are close to the model consensus and guidance provided by the NOAA Ocean Prediction Center. FORECAST POSITIONS AND MAX WINDS INIT 04/0300Z 24.9N 73.2W 55 KT 65 MPH 12H 04/1200Z 27.3N 73.7W 60 KT 70 MPH 24H 05/0000Z 30.8N 73.4W 65 KT 75 MPH 36H 05/1200Z 34.1N 72.0W 65 KT 75 MPH 48H 06/0000Z 36.9N 69.0W 65 KT 75 MPH 72H 07/0000Z 42.2N 59.5W 60 KT 70 MPH 96H 08/0000Z 47.5N 50.0W 50 KT 60 MPH...POST-TROP/EXTRATROP 120H 09/0000Z 49.5N 40.0W 50 KT 60 MPH...POST-TROP/EXTRATROP $$ Forecaster Brown

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Tropical Storm BERTHA Forecast Discussion Number 12

2014-08-03 22:41:27| National Hurricane Center (Atlantic)

Issued at 500 PM EDT SUN AUG 03 2014 000 WTNT43 KNHC 032041 TCDAT3 TROPICAL STORM BERTHA DISCUSSION NUMBER 12 NWS NATIONAL HURRICANE CENTER MIAMI FL AL032014 500 PM EDT SUN AUG 03 2014 After Bertha's cloud pattern became a little better organized earlier today, there has been little change in its overall appearance over the past several hours. There are limited banding features over the eastern semicircle of the circulation, and the deep convection is a little ragged-looking. The upper-level outflow is becoming a little better defined, but there is still some northwesterly shear over the system. The current intensity is kept at 40 kt based on earlier observations from the Hurricane Hunter aircraft. The numerical guidance has become a little less bullish on future strengthening, but the Decay-SHIPS model still calls for the cyclone to become a hurricane in 60-72 hours, as does the official forecast. It should be noted, however, that the intensity model consensus no longer predicts Bertha to become a hurricane. Based on an earlier center fix from the aircraft, the working best track has been adjusted a little to the east of the previous estimates. The center location is not obvious on the latest visible imagery, and the initial motion estimate is a somewhat uncertain 325/16 kt. The track forecast for the next 48 hours or so is slightly complicated by a low- to mid-level disturbance that is currently near Florida. The U.K. Met. Office global model forecast shows Bertha interacting with this disturbance and moving a little closer to the United States east coast than earlier runs. Other global models such as the GFS do not show as much interaction and keep Bertha farther offshore. The new official track forecast has been nudged a little to the left of the previous one and is very close to a consensus of the latest GFS and ECMWF solutions. FORECAST POSITIONS AND MAX WINDS INIT 03/2100Z 23.3N 73.2W 40 KT 45 MPH 12H 04/0600Z 25.8N 73.8W 45 KT 50 MPH 24H 04/1800Z 29.0N 74.0W 50 KT 60 MPH 36H 05/0600Z 32.6N 73.2W 55 KT 65 MPH 48H 05/1800Z 35.7N 71.2W 60 KT 70 MPH 72H 06/1800Z 40.5N 63.0W 65 KT 75 MPH 96H 07/1800Z 46.0N 53.5W 55 KT 65 MPH...POST-TROP/EXTRATROP 120H 08/1800Z 50.0N 44.0W 50 KT 60 MPH...POST-TROP/EXTRATROP $$ Forecaster Pasch

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Hurricane ISELLE Forecast Discussion Number 13

2014-08-03 22:39:29| National Hurricane Center (East Pacific)

Issued at 200 PM PDT SUN AUG 03 2014 000 WTPZ44 KNHC 032039 TCDEP4 HURRICANE ISELLE DISCUSSION NUMBER 13 NWS NATIONAL HURRICANE CENTER MIAMI FL EP092014 200 PM PDT SUN AUG 03 2014 The cold cloud tops of Iselle's convection have suddenly begun to expand during the past few hours, suggesting that vertical shear is relaxing. The eye has become a little more distinct, and the hurricane appears to be taking on a more circular, compact shape. Current intensity estimates remain unchanged from earlier this morning, so the initial intensity is held at 100 kt. Regarding the compact shape of the hurricane, conventional and microwave images seem to suggest that Iselle is losing its convective banding features. And, for the first time, the Annular Hurricane Index is indicating that Iselle has a marginal annular structure. If it does in fact become annular, then the hurricane is likely to only gradually weaken during the next couple of days in an environment of light easterly shear and slowly decreasing sea surface temperatures. Increasing vertical shear and even colder waters should induce a faster weakening trend after 48 hours, but most of the guidance still suggests that Iselle will maintain tropical storm status as it moves near the Hawaiian Islands on days 4 and 5. The NHC intensity forecast is essentially unchanged from the previous one and lies very close to the LGEM and intensity consensus ICON for the entire forecast period. The latest center fixes suggest that Iselle jogged west- northwestward earlier today, but the estimated initial motion is now westward, or 280/9 kt. The hurricane is expected to slow down a little during the next 36 hours coincident with a developing break in the subtropical ridge. A mid-level high is then forecast to develop between Hawaii and California by day 3, which should steer Iselle at a faster rate toward the west-northwest through the end of the forecast period. There is very little spread among the track models, but the entire envelope has shifted northward on days 3 through 5. Further shifts could be required if the models continue their recent trends, but at this point Iselle is still a potential threat to the Hawaiian Islands later this week. FORECAST POSITIONS AND MAX WINDS INIT 03/2100Z 15.7N 133.7W 100 KT 115 MPH 12H 04/0600Z 15.8N 135.1W 95 KT 110 MPH 24H 04/1800Z 15.8N 136.8W 90 KT 105 MPH 36H 05/0600Z 15.8N 138.3W 85 KT 100 MPH 48H 05/1800Z 16.0N 140.0W 75 KT 85 MPH 72H 06/1800Z 17.5N 145.0W 60 KT 70 MPH 96H 07/1800Z 19.5N 151.5W 50 KT 60 MPH 120H 08/1800Z 21.5N 157.5W 45 KT 50 MPH $$ Forecaster Berg

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Tropical Storm BERTHA Forecast Discussion Number 11

2014-08-03 16:35:08| National Hurricane Center (Atlantic)

Issued at 1100 AM EDT SUN AUG 03 2014 000 WTNT43 KNHC 031435 TCDAT3 TROPICAL STORM BERTHA DISCUSSION NUMBER 11 NWS NATIONAL HURRICANE CENTER MIAMI FL AL032014 1100 AM EDT SUN AUG 03 2014 Visible satellite imagery shows that the cloud pattern of Bertha is becoming a little better organized, with some banding features apparent over the eastern portion of the system. Also, reports from a hurricane hunter aircraft indicate that the low-level circulation is becoming better defined. The current intensity estimate is held at 40 kt, in agreement with SFMR-observed surface winds from the aircraft well to the northeast of the estimated center. The initial motion estimate continues to be northwestward, or 320/18 kt. The track forecast and reasoning are mostly unchanged from the previous advisory. Over the next couple of days, Bertha should move around the western periphery of a mid-tropospheric anticyclone at a slightly slower forward speed. Thereafter, the tropical cyclone is likely to turn northeastward and east-northeastward while accelerating as it moves into the mid-latitude westerlies. The current official forecast is fairly close to the latest multi-model consensus. Cirrus motions and animation of water vapor imagery show that the shear over Bertha has begun to relax a little, and this, along with an increase in mid-level moisture, should allow for some strengthening. In the latter part of the forecast period, west-southwesterly shear increases significantly, but by that time it is anticipated that Bertha will have become an extratropical storm over the North Atlantic. The official wind speed forecast is the same as in the previous advisory, and quite similar to the latest intensity model consensus, ICON. FORECAST POSITIONS AND MAX WINDS INIT 03/1500Z 22.2N 72.6W 40 KT 45 MPH 12H 04/0000Z 24.3N 73.7W 45 KT 50 MPH 24H 04/1200Z 27.4N 74.3W 50 KT 60 MPH 36H 05/0000Z 30.7N 73.6W 55 KT 65 MPH 48H 05/1200Z 33.7N 71.7W 60 KT 70 MPH 72H 06/1200Z 39.5N 64.5W 65 KT 75 MPH 96H 07/1200Z 44.0N 55.0W 60 KT 70 MPH...POST-TROP/EXTRATROP 120H 08/1200Z 47.5N 43.0W 50 KT 60 MPH...POST-TROP/EXTRATROP $$ Forecaster Pasch

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