Average 19 year old weather nerd. Sophomore @ Plymouth State University, majoring in meteorology, with the goal of becoming a professional forecaster
By: MAweatherboy1 , 11:14 PM GMT on September 11, 2012
The tropics remain active as we remain near the peak of hurricane season. Officially we are on the other side of the peak now, and we should begin a slow but steady decline in number of storms until the season officially ends on November 30. The Atlantic has been very busy in the past couple of weeks, but it has calmed today as former Hurricane Leslie has been declared extratropical after a landfall on Newfoundland and former Major Hurricane Michael dissipated over the open waters of the Atlantic today.
Figure 1: The remains of Michael are clearly visible, as he is now just a convectionless swirl. This remnant low should continue to weaken and eventually dissipate altogether.
Tropical Depression 14 Forms
Taking the place of Leslie and Michael is Tropical Depression 14, which formed earlier today. As of the latest (5PM EDT) advisory from the National Hurricane Center, TD 14 is located about 1170 miles E of the Lesser Antilles and is moving NW at 12mph. TD 14 currently has maximum 1 minute sustained winds of 35mph and a minimum central pressure of 1006mb.
Forecast For TD 14
Tropical Depression 14 will be in a favorable environment of low shear for the next 3-4 days, so strengthening is likely during this time. It is likely TD 14 will become Tropical Storm Nadine tonight, and the NHC forecasts a peak intensity of 75mph in about 3 days, which would make the system a minimal hurricane. Due to the good structure of TD 14 and the very conducive environment for strengthening it has for the next few days, I think the NHC forecast is probably conservative as I am expecting a peak of 90-100mph on Friday or Saturday. After this time, wind shear will increase significantly over the storm and weaken it. TD 14 will likely be a typical recurving storm as it should continue to track NW, then NNW, then N, and eventually NE as the subtropical ridge over the Atlantic breaks down. TD 14 will not be a threat to the US or Bermuda, but interests in the Azores should keep an eye on the system as impacts there cannot be ruled out.
Figure 2: Tropical Depression 14, showing good overall structure but some convective disorganization.
Figure 3: Official NHC forecast for TD 14.
Elsewhere in the Atlantic it is mostly quiet with no invests and no areas currently being monitored for development by the NHC. The wave train continues off of Africa, and it is probable we will see at least another storm or two before Cape Verde season winds down towards the end of the month and our focus shifts closer to home in the Caribbean.
Invest 90E May Develop In East Pacific
The East Pacific came roaring out of the gate this year, producing storm after storm, but it has slowed significantly into the middle of the season and has not produced a major system in a while. There is currently one area of disturbed weather being watched out there, Invest 90E. 90E is a large disturbance that has been slowly consolidating, and it is being given a 70% chance of development in the next 48 hours by the NHC. There is also a Tropical Cyclone Formation Alert issued for it. The center of 90E is located well off the coast of Mexico, and it is moving WNW at about 10mph, meaning it is moving away from the coast and should not threaten land. I give 90E about a 60% chance of developing in the next 48 hours based on its large size and need for further consolidation, but a 90% chance of the disturbance developing at any point in its life.
Figure 4: Invest 90E
Sanba Strengthening, Targeting Koreas
After an extended dry spell, the West Pacific has roared to life once again as another potentially powerful storm is forming out there, Tropical Storm Sanba. As of the latest advisory from the Joint Typhoon Warning Center, Sanba has maximum 1 minute sustained winds of 50mph. It is located about 700 nautical miles east of Manila, Philippines, and is moving slowly NW at just 5kts.
Forecast For Sanba
Sanba has the potential to become a dangerous storm. It is over and will continue to be over extremely warm waters of up to 30C, and has favorable upper level conditions to work with. The official JTWC forecast indicates steady strengthening for the next 4 days with a peak of 100kts, or 115mph, which would make Sanba a major hurricane. In general, I agree with the forecast reasoning, but there is one problem that I see: In the time since the issuance of the advisory a few hours ago, Sanba has seemingly intensified quite quickly, with deep convection wrapping around the whole system and an eye forming. This eye is very evident in microwave imagery and can be seen on satellite, so it is likely Sanba is at around 60-65kts right now. If this trend of rapid intensification continues, the 24 hour intensity forecast calling for a 65kt hurricane may be off by as much as 20kts. This would potentially mean the listed intensities are too low, and the peak may be closer to 115-125kts as conditions appear favorable for this intensification to continue. The main steering feature for Sanba is a building subtropical ridge that will keep the storm on a fairly straight NW heading for much of the forecast period, with a more NNW turn likely in 5 days or so. This track brings the storm in the direction of southern Japan and the Korean Peninsula. Interests in these areas should monitor the progress of this storm very closely as it appears likely landfall will be made somewhere in that area in 5-6 days.
Figure 5: Official JTWC forecast track for Sanba.
Figure 6: Tropical Storm Sanba. An eye is apparent, and the storm is likely at or near typhoon intensity.
Figure 7: Microwave image of Sanba, with the eye very clear.
Thank you for reading, and have a great night!
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