TROPICAL CYCLONE FORMATION: HURRICANE GASTON / T.D. 8 / T.D 9 / INVEST 92L (40%)
Disclaimer: This site is not affiliated with the National Hurricane Center, Storm Prediction Center, or National Weather Service. ALL forecasts herein are the result of my analysis, and I am solely responsible for the content.
(T. F. “Storm” Walsh III)
For those who have donated to my site, your help has been greatly appreciated. For those not aware, donations to my site help me offset my personal out of pocket expenses…such as some of the model maps you view on here, are only available due to my subscription to the corresponding site. The F5 Data maps I post, also another out of pocket expense (monthly subscription). Updates to software (weather related), and costs for my domain name are also out of pocket to me. To donate, please click the DONATE button to the right. Any help you provide is immensely appreciated! Although it may seem I am not here and working in support of your donation, I have to work my forecasting time around my ever changing work schedule.
CURRENT 2016 ATLANTIC TROPICAL CYCLONE TOTALS:
TOTAL STORMS: 7
MAJOR HURRICANES: 1
StormW’s Seasonal Hurricane Forecast:
TOTAL STORMS: 13-15
INTENSE HURRICANES: 3-4
Good day everyone!
GASTON is still a hurricane (CAT2) at the moment. There has been no change in the forecast as far as strength and track. GASTON is expected to weaken at a more steady pace in about 72 hours, and the projected steering flow should continue to carry him toward the NE, with a turn more toward the ENE in 48 hours, bringing him close to the Azores in about 72 hours.
Closer to home, Tropical Depression EIGHT has remained poorly organized overnight, and into the early morning hours. However recent satellite loop imagery indicates a blowup of convection over the last reported center. As of the 11:00 a.m. EDT intermediate advisory, the following was available on T.D. 8:
11:00 AM EDT Tue Aug 30
Location: 34.2°N 75.3°W
Moving: NNW at 5 mph
Min pressure: 1011 mb / 29.85 in
Max sustained: 35 mph
The has been under the influence of westerly shear, however the wind shear forecast does indicate a brief period where the shear intensity relaxes…this may be occurring at the moment, based on the blowup of convection over the center. Based on this, and the position over the Gulfstream, T.D. EIGHT should continue with some brief, slow organization and development, and could become a Tropical Storm by this evening, or tomorrow. The NHC discussion indicates this system to attain Tropical Storm strength in 24 hours. A Tropical Storm WARNING remains in effect for a portion of the OBX.
NHC INTENSITY GUIDANCE
INIT 30/1500Z 34.2N 75.3W 30 KT 35 MPH
12H 31/0000Z 34.8N 75.2W 35 KT 40 MPH
24H 31/1200Z 35.7N 74.1W 35 KT 40 MPH
36H 01/0000Z 37.2N 71.6W 40 KT 45 MPH
48H 01/1200Z 39.4N 67.3W 45 KT 50 MPH|
72H 02/1200Z 45.0N 53.0W 45 KT 50 MPH…POST-TROP/EXTRATROP
The depression is currently moving to the NNW, and based on forecast steering, I expect this motion to continue until later today, to when a turn north should occur. By tomorrow, the presence of an approaching trof should begin to turn it toward the NE and begin to steer it away from the U.S. coast. This is reflected both in the dynamic guidance, and NHC forecast track.
Residents along the OBX should closely monitor this system, as the threat of flash flooding and downed trees may be likely as the system makes its CPA (Closest Point of Approach)
Residents should monitor NOAA Weather Radio and local NWS statements and warnings regarding this system
T. D. 8 NWS LOCAL STATEMENT
Elsewhere,Tropical Depression NINE still remains somewhat disorganized NW of the Yucatan Channel. As of the 11:00 a.m. EDT advisory from the NHC, the following was available on the depression:
10:00 AM CDT Tue Aug 30
Location: 24.0°N 87.2°W
Moving: WNW at 7 mph
Min pressure: 1004 mb / 29.65 in
Max sustained: 35 mph
Recent satellite loop imagery indicated the LLC to now be just slightly to the NW of the heavy convection, with the convection building very close to the center. The depression has still had the battle of wind shear from the NW, however the westward motion over the past day has put the depression in an area where this shear has reduced from 25-30 knots, down to 15-20 knots.
The current wind shear forecast shows models in agreement of the shear magnitude relaxing during the next 12 hours, dropping to favorable values. The GFS and ECMWF models are both in fair agreement, of the current upper level anticyclone becoming established either over, or very near the center of the depression, and keeping it maintained over the system throughout the forecast period. Based on this, I believe we should begin to witness more of a slow but steady increase in organization and development, and it is possible the depression could become a Tropical Storm by this evening or early tomorrow. This is reflected in the NHC intensity forecast. Current intensity model guidance also agrees with this, as well as only making this system a moderate to strong Tropical Storm. Having analyzed the shear and 200 mb pattern forecast, one would tend to believe the system would be stronger prior to landfall. However, the NHC does mention the existence of mid level dry air, which is noted in water vapor loop imagery. The presence of this drier air is probably going to be the inhibiting factor in that the system may not make it to hurricane strength. I am not expecting the dry air to be too terribly detrimental, as far as killing the system, as the depression still retains a high amount of TPW (Total Precipitable Water). Based on these combined factors, I have to concur with the NHC intensity forecast at the moment.
The report from the NHC is that the depression is moving to the WNW at 7 mph, and close examination of various satellite loop imagery channels tend to indicate this over the past couple of hours, which would tend to coincide with the last updated layer mean steering map from CIMSS.
INIT 30/1500Z 24.0N 87.2W 30 KT 35 MPH
12H 31/0000Z 24.5N 87.3W 35 KT 40 MPH
24H 31/1200Z 25.4N 87.4W 40 KT 45 MPH
36H 01/0000Z 26.9N 86.2W 45 KT 50 MPH
48H 01/1200Z 28.5N 84.5W 50 KT 60 MPH
72H 02/1200Z 31.6N 79.0W 50 KT 60 MPH
96H 03/1200Z 34.0N 72.0W 50 KT 60 MPH
120H 04/1200Z 36.5N 66.0W 60 KT 70 MPH…POST-TROP/EXTRATROP
Based on the latest dynamic guidance, the consensus has shifted slightly left, but remains close to the NHC offical track. Current steering is somewhat weak, hence the slow movement. Based on analysis of the recent forecast steering layers maps, I have no change in forecast track thinking, which translates into the dynamic guidance and NHC track. The forecast still calls for the ridge which has been over the Mid Atlantic states over the past few days to continue to retrograde west (as noted in current steering) and is forecast to weaken / collapse as a digging trof approaches in about 36 hours. This should allow the system to come under the effect of the trof, with the western most Atlantic subtropical ridge combined with the trof, to become the dominant steering factor. Based on this analysis, I concur with the dynamic guidance, and the current NHC forecast track.
Currently, there are no watches or warnings issued, however NHC still indicates this may change for some portions of the wets Florida coast and is reflected in the 5:00 a.m. EDT discussion:
NHC FORECAST DISCUSSION
EXCERPT FROM THE DISCUSSION:
Given the current forecast, a tropical storm watch may be required for a portion of the Florida Gulf coast later today.
Based on forecast track, we are still looking at probable landfall in the Big Bend region. However, given the large circulation, residents on the eastern portion of the system, may very well experience times of heavy rainfall, which could allow for flooding of low lying areas and some urban flooding. For the Tampa Bay area, the current forecast places us just out of the tropical storm force winds area, however depending on how this strengthens, and exactly where landfall occurs, will determine how much rainfall, and the intensity of winds.
From the NHC advisory:
HAZARDS AFFECTING LAND
RAINFALL: The depression is expected to produce additional rain accumulations of 2 to 4 inches over western Cuba through Wednesday, with maximum storm total amounts up to 12 inches. These rains could cause life-threatening flash floods and mud slides. Storm total rainfall amounts of 5 to 10 inches are possible over much of the Florida peninsula through Friday morning, with isolated maximum amounts of 15 inches possible. This rainfall may cause flooding and flash flooding.
The QPF (Quantitative Precipitation Forecast) from NOAA WPC indicates the following total rainfall potential over the next 3-5 days:
1-3 DAY FORECAST
CURRENT SEA HEIGHT AND WIND FORECAST FROM STORMSURF MODEL (click for animation)
Residents along the Florida west coast should closely monitor the progress of this system, NOAA Weather Radio, and local NWS office statements and warnings regarding this system. The following map is linked. Click on your area of interest for local NWS information.
Elsewhere, a tropical wave has exited Africa, and is now in the far EATL. The last update I have on this, is from last night. As of the 8:00 p.m. EDT ATCF BTK product, the following information was available on the INVEST 92L:
8:00 PM EDT Mon Aug 29
Location: 15.5°N 16.5°W
Moving: W at 15-20 mph
Min pressure: 1008 mb / 29.77 in
Max sustained: 25 mph
INVEST 92L is not as impressive as yesterday, based on satellite loop imagery, however this has a rather large circulation. The current wind shear products indicated somewhat favorable upper level winds and an anticyclone over the system. Based on current thinking in forecast track, upper level winds may relax a bit more in about 3-4 days, with the upper level feature becoming more compact and established. Based on this, and the supposed improvement of the overall environment, two of which consists of the MJO becoming more of a presence over the Atlantic basin, and improvement of the 200 mb velocity potential pattern to favorable conditions. Based on forward speed however, organization and development may be slow to occur over the next. This may be why the NHC graphic shows the hatched area further west, and would make sense, since this is where conditions are currently forecast to become more favorable.
Current forecast path thinking has not changed on my prat, and the INVEST should continue on a general westerly path over the next 4-5 days. Forecast steering indicates the ridge guiding this at the moment, continues to build west, in tandem with the INVEST in such a manner, that the INVEST remains just ever so slightly west of the ridge center, or axis, which would allow for a more westward track in the forecast period. Based on the NHC TWO graphic, it appears they like the morning run of the ECMWF, which keeps the system further south than the current GFS run from earlier this morning.
I will continue to monitor all this, and should have another update tomorrow, but late afternoon. Tomorrow will be my last update, as I work Thu- Sat.
Have a blessed day!
T. F. “STORM” WALSH III
GMCS, USCG (ret)
METEOROLOGIST / HURRICANE SPECIALIST /SEVERE WEATHER SPECIALIST
MEMBER WEST CENTRAL FLORIDA AMS