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Tropical Storm DOUGLAS Forecast Discussion Number 15

2014-07-02 10:55:11| National Hurricane Center (East Pacific)

Issued at 200 AM PDT WED JUL 02 2014 000 WTPZ44 KNHC 020855 TCDEP4 TROPICAL STORM DOUGLAS DISCUSSION NUMBER 15 NWS NATIONAL HURRICANE CENTER MIAMI FL EP042014 200 AM PDT WED JUL 02 2014 A flareup of deep convection in the northern semicircle has developed during the past few hours even though Douglas is now moving over sub-26C sea-surface temperatures. A 02/0528 UTC ASCAT-B overpass indicated a couple of 39-kt wind vectors in the northwestern quadrant of the cyclone, so the initial intensity is being maintained at 40 kt for this advisory. Douglas is moving slowly northwestward or 325/03 kt. Steering currents surrounding the cyclone are expected to remain weak for the next couple of days as Douglas remains trapped in a weakness in the subtropical ridge that extends from Baja California westward across the eastern North Pacific. As the cyclone weakens over colder water and becomes more vertically shallow, it should be steered westward by the low-level trade wind flow by day 3 and beyond. The track forecast is is similar to the previous advisory track and is close to the consensus track model TVCE. Despite the recent aforementioned resurgence in convection and very light vertical wind shear, Douglas is not long for this world. The cyclone is currently located over sub-26C SSTs, and the water ahead of the cyclone only gets colder while the surrounding air mass is becoming drier and more stable as well. Therefore, gradual weakening is forecast by 12 hours and beyond, and Douglas is expected to become a remnant low by 48 hours, if not sooner. The NHC intensity forecast is identical to the previous forecast and closely follows the intensity consensus model IVCN. FORECAST POSITIONS AND MAX WINDS INIT 02/0900Z 19.6N 116.0W 40 KT 45 MPH 12H 02/1800Z 19.8N 116.1W 35 KT 40 MPH 24H 03/0600Z 20.2N 116.4W 35 KT 40 MPH 36H 03/1800Z 20.6N 116.7W 30 KT 35 MPH 48H 04/0600Z 21.1N 117.5W 25 KT 30 MPH...POST-TROP/REMNT LOW 72H 05/0600Z 22.2N 119.9W 25 KT 30 MPH...POST-TROP/REMNT LOW 96H 06/0600Z 23.0N 122.8W 20 KT 25 MPH...POST-TROP/REMNT LOW 120H 07/0600Z 23.0N 125.8W 20 KT 25 MPH...POST-TROP/REMNT LOW $$ Forecaster Stewart

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Tropical Storm DOUGLAS Forecast Discussion Number 14

2014-07-02 04:56:48| National Hurricane Center (East Pacific)

Issued at 800 PM PDT TUE JUL 01 2014 000 WTPZ44 KNHC 020256 TCDEP4 TROPICAL STORM DOUGLAS DISCUSSION NUMBER 14 NWS NATIONAL HURRICANE CENTER MIAMI FL EP042014 800 PM PDT TUE JUL 01 2014 Douglas has maintained a tight curved band of deep convection near its center, primarily within the western semicircle. Consequently, the TAFB and SAB Dvorak CI numbers have remained the same and thus the intensity is kept at 40 kt. While Douglas should remain under light vertical shear for the next few days, the gradually cooling waters and drier stable air that the cyclone will encounter should cause the convection to diminish and, in about 36-48 hours, eventually to cease. The large size of Douglas suggests that it will wind down gradually, even if the convection dissipates quicker than expected. The intensity forecast is based upon the tight consensus of intensity models and is nearly the same as that in the previous advisory. Douglas has been meandering this evening with a longer-term motion of 340/2. The steering for the cyclone has nearly collapsed as the mid-level ridge to the north has weakened due to a short-wave trough impinging upon it. As Douglas becomes a weaker, shallower vortex, it should be advected faster toward the west-northwest in about 3 days and then westward by day 5 in the low-level tradewind flow. The track forecast is based upon the tightly clustered multi-model consensus - TVCE - with somewhat less weight placed upon the ECMWF model, since this model has had a distinct equatorward bias for Douglas. This track prediction is slightly poleward of that from the previous advisory. FORECAST POSITIONS AND MAX WINDS INIT 02/0300Z 19.4N 115.7W 40 KT 45 MPH 12H 02/1200Z 19.7N 115.9W 35 KT 40 MPH 24H 03/0000Z 20.1N 116.1W 35 KT 40 MPH 36H 03/1200Z 20.4N 116.4W 30 KT 35 MPH 48H 04/0000Z 20.8N 116.9W 25 KT 30 MPH...POST-TROP/REMNT LOW 72H 05/0000Z 22.0N 119.0W 25 KT 30 MPH...POST-TROP/REMNT LOW 96H 06/0000Z 23.0N 122.0W 20 KT 25 MPH...POST-TROP/REMNT LOW 120H 07/0000Z 23.0N 125.0W 20 KT 25 MPH...POST-TROP/REMNT LOW $$ Forecaster Landsea

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Tropical Storm ARTHUR Forecast Discussion Number 5

2014-07-02 04:52:40| National Hurricane Center (Atlantic)

Issued at 1100 PM EDT TUE JUL 01 2014 000 WTNT41 KNHC 020252 TCDAT1 TROPICAL STORM ARTHUR DISCUSSION NUMBER 5 NWS NATIONAL HURRICANE CENTER MIAMI FL AL012014 1100 PM EDT TUE JUL 01 2014 Data from the Melbourne WSR-88D radar indicates that Arthur has a complex structure this evening. A mid-level cyclonic circulation accompanied by a possible eye feature is clearly evident near 27.8N 78.8W. However, the motions of the light showers/low clouds seen in the radar data suggest that the low-level center is about 25-30 n mi west of the mid-level center. Air Force Reserve and NOAA Hurricane Hunter aircraft are scheduled to investigate Arthur early Wednesday morning to see if the center has re-formed to the east. Pending the arrival of the aircraft, the initial intensity remains 45 kt. The initial motion is a rather uncertain 360/2. The track guidance models remain in good agreement on a large mid/upper-level trough digging southeastward into the northeastern and mid-Atlantic states during the next 72 hours, while a subtropical ridge east of the Carolinas gradually strengthens. The combination of these two systems is expected steer Arthur generally northward for 24 hours or so, followed by a turn toward the northeast and gradual acceleration. The combination of the lack of motion over the past 6-12 hours and the slightly more eastward initial position have resulted in some eastward shift of the track guidance envelope. As a result, the new forecast track is also shifted slightly to the east from the previous forecast. The official forecast is near the center of the track guidance envelope and remains close to the various consensus models. Arthur is expected to be in an environment of light northwesterly vertical wind shear for the next 60-72 hours. This should allow for continued development. However, satellite total precipitable water data suggests that pockets of dry air remain near the cyclone, and these could hinder development. Given these competing factors, the new intensity forecast is changed little from the previous forecast and calls for Arthur to become a hurricane in about 36 hours and reach its peak intensity in about 72 hours. After that time, the cyclone should undergo extratropical transition and weaken as it merges with the mid/upper-level trough. Based on the new forecast track, additional watches and warnings are not necessary for the North Carolina and South Carolina coasts at this time. However, tropical storm or hurricane watches will likely be required for portions of these areas on Wednesday. FORECAST POSITIONS AND MAX WINDS INIT 02/0300Z 27.9N 79.2W 45 KT 50 MPH 12H 02/1200Z 28.6N 79.3W 50 KT 60 MPH 24H 03/0000Z 29.7N 79.2W 60 KT 70 MPH 36H 03/1200Z 31.0N 78.7W 65 KT 75 MPH 48H 04/0000Z 32.8N 77.3W 75 KT 85 MPH 72H 05/0000Z 37.5N 72.0W 80 KT 90 MPH 96H 06/0000Z 43.0N 64.0W 60 KT 70 MPH...POST-TROP/EXTRATROP 120H 07/0000Z 47.5N 57.0W 45 KT 50 MPH...POST-TROP/EXTRATROP $$ Forecaster Beven

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Tropical Depression ELIDA Forecast Discussion Number 7

2014-07-02 04:52:40| National Hurricane Center (East Pacific)

Issued at 800 PM PDT TUE JUL 01 2014 000 WTPZ45 KNHC 020252 TCDEP5 TROPICAL DEPRESSION ELIDA DISCUSSION NUMBER 7 NWS NATIONAL HURRICANE CENTER MIAMI FL EP052014 800 PM PDT TUE JUL 01 2014 Elida remains a tight swirl of low clouds devoid of any deep convection. The initial intensity has been lowered to 30 kt, close to a blend of the latest T/CI numbers from TAFB. Strong northwesterly shear over Elida should continue to weaken the system. Model guidance is in good agreement on this solution, and the new NHC intensity prediction is very close to the previous one. The only significant change is to show remnant low status within 24 hours. Given the lack of convection, however, Elida could become a remnant low even sooner than forecast. Elida is moving a little faster toward the southeast this evening - roughly 135/3 - an unusual motion for an eastern Pacific cyclone in July. The depression or its remnants will likely move southward by late tomorrow, then westward by Thursday due to a building low-level ridge over the eastern Pacific. Model guidance has shifted southward on this cycle, and the NHC forecast is moved in that direction. The small cyclone should degenerate into a trough in 3-4 days, which is in line with the global models. FORECAST POSITIONS AND MAX WINDS INIT 02/0300Z 17.0N 103.4W 30 KT 35 MPH 12H 02/1200Z 16.7N 103.2W 25 KT 30 MPH 24H 03/0000Z 16.4N 103.3W 20 KT 25 MPH...POST-TROP/REMNT LOW 36H 03/1200Z 16.2N 103.6W 20 KT 25 MPH...POST-TROP/REMNT LOW 48H 04/0000Z 16.1N 104.5W 20 KT 25 MPH...POST-TROP/REMNT LOW 72H 05/0000Z 16.5N 107.0W 15 KT 15 MPH...POST-TROP/REMNT LOW 96H 06/0000Z...DISSIPATED $$ Forecaster Blake

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Tropical Storm ARTHUR Forecast Discussion Number 4

2014-07-01 22:53:10| National Hurricane Center (Atlantic)

Issued at 500 PM EDT TUE JUL 01 2014 000 WTNT41 KNHC 012053 TCDAT1 TROPICAL STORM ARTHUR DISCUSSION NUMBER 4 NWS NATIONAL HURRICANE CENTER MIAMI FL AL012014 500 PM EDT TUE JUL 01 2014 Although radar and satellite imagery indicate that the convective pattern of Arthur has changed little since the previous advisory... an Air Force Reserve reconnaissance aircraft investigating the cyclone this afternoon has found that flight-level and SFMR surface winds in the southeastern quadrant that support increasing the intensity to 45 kt. In fact, the flight crew has been been bounced around pretty good by strong thunderstorms in that area and have been forced to climb to a higher altitude in order to avoid significant turbulence. Arthur has been drifting northwestward at 325/02 kt. No significant change has been made to the previous forecast track or reasoning. The latest reliable numerical models remain in good agreement on large mid-level trough digging southeastward into the northeastern and mid-Atlantic states during the next 72 hours, while a subtropical ridge east of the Carolinas gradually strengthens. The combination of these two systems is expected to steadily increase the southwesterly steering flow over the southeastern United States and the extreme western Atlantic. By Days 4 and 5, Arthur is forecast to accelerate rapidly northeastward ahead of the aforementioned trough as an extratropical cyclone. The official forecast track is again just an update of the previous advisory track, and remains in the middle of the tightly packed guidance envelope and close to the consensus model TVCA. Northwesterly vertical wind shear is expected to gradually abate over the next 48 hours, allowing Arthur to develop an upper-level outflow pattern that is conducive to strengthening. The primary inhibiting factor will be the occasional intrusions of dry mid-level air to the north of the cyclone penetrating into the center and briefly disrupting the inner-core convection. However, the global and regional models are forecasting the inner core region to moisten significantly by 36-48 hours, which should allow Arthur to strengthen into a hurricane while the cyclone is over warm SSTs and in light shear conditions. After 72 hours, Arthur will be be moving over cooler water and is forecast to experience vertical wind shear in excess of 30 kt, which should induce at least steady weakening. The NHC intensity forecast closely follows the consensus model IVCN. FORECAST POSITIONS AND MAX WINDS INIT 01/2100Z 27.8N 79.4W 45 KT 50 MPH 12H 02/0600Z 28.3N 79.4W 50 KT 60 MPH 24H 02/1800Z 29.2N 79.5W 55 KT 65 MPH 36H 03/0600Z 30.4N 79.2W 60 KT 70 MPH 48H 03/1800Z 32.1N 78.3W 70 KT 80 MPH 72H 04/1800Z 36.6N 73.6W 80 KT 90 MPH 96H 05/1800Z 42.2N 65.5W 60 KT 70 MPH...POST-TROP/EXTRATROP 120H 06/1800Z 46.8N 57.5W 45 KT 50 MPH...POST-TROP/EXTRATROP $$ Forecaster Stewart

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