Our 2 disturbances in the tropical Atlantic have received invest status last night and this morning which opens up mountains of new information about them. I’ll dig through it and do my best to explain it below.
By the numbers:
2 invests (97L and 96L)
1 TS (KIKO)
2 day probability of formation into TD/5 day probability of formation into a TD
97L- NHC 10/10
96L- NHC 30/30
KIKO- 60 mph, 1000mb
More details on all systems below.
Atlantic Tropical weather outlook (TWO)
Eastern Pacific Tropical weather outlook (TWO)
I’ll start with the one closest to the Caribbean Islands designated 97L by the NHC this morning.
Mid afternoon satellite image of 97L.
The forecast for 97L… Now that this system is an invest, the specially designed hurricane models can weigh in on the forecast. The 2 images below show the intensity forecast and the track forecast from the models.
The intensity forecast from the hurricane models for 97L.
The shaded patches are the different classifications. The bottom white swath is tropical depression status while the middle grey swath is tropical storm status and the uppermost white swath is CAT 1 hurricane status. Read more about tropical cyclone classification here. Read more about hurricane models here.
This map shows the hurricane models depiction of the storms track.
NOTE: these are just model depictions and are not official forecasts.
Intensity: The models and I are in unanimous agreement that this storm will likely reach tropical storm intensity at some point. Where we differ, is when. I expect the storm to lose a large part of its convection during the diurnal minimum, the time of day where there is the sun’s energy is at its weakest point during the day.Read more about this phenomenon here.
However, DMAX will greet the system bright and early tomorrow morning and will allow for significant return of convection to the system. There is a modest amount of spin associated with this system and with a bit more convection (may happen tomorrow or Labor Day), it could reach TD status. However, there are a few factors suppressing development and one of those is shear.
This map indicated wind shear in the yellow contours and the upper air wind direction in the tan-ish lines and arrows. Notice the clockwise rotation shown by those arrows over 97L. That is an upper air anticyclone or high pressure. This helps act as a shear force-field and it also shows signs of a healthy upper outflow pattern.
This graphic shows some of the things that 97L needs to work on. Lets start at the top left. This box indicates an outflow cloud-for lack of better word- which forms when thunderstorms collapse inward and generate a massive burst of wind known as a mirco or macro burst depending on the scale. This sudden release of energy containing cool air from aloft spreads along the surface there warm, moist air resides. The clash of warm and cool creates a cloud.
These clouds signal an unhealthy storm by indicating thunderstorms inside it are dying which decreases its capability to harness the latent heat energy that it depends on. Think of it like a wind turbine suddenly losing its capability to harness the wind energy. Same concept.
The upper right square shows the lack of healthy upper air outflow in 3/4 quadrants of the system. This must also be resolved before it can become a healthy storm. The upper air outflow is a phenomenon that whisks away cool, dry air from the center of the storm to the fringes of the system making more room for warm moist air to take its place.
Here is a little graphic to show outflow in a hurricane.
The bottom 2 squares are the same thing in different colors. They are microwave imagery that capture the location and intensity of the strongest thunderstorms in a system like this. Notice there are very few bright red dots indicating an absence of strong thunderstorms and therefore, the absence of a functioning storm.
This graphic shows the 3 main features of 97L. The APPROXIMATE center, the strongest thunderstorms and what outflow channel it has. All 3 areas must improve greatly before TD status can be attained.
Track- This all depends on intensity. As discussed in yesterday’s post, if a storm is strong enough, then it will be more capable of being tugged north by a trough in the upper levels of the atmosphere. This is what will have the most effect on track.
This is where I expect the storm to track through the next few days. However, uncertainties still abound and this map will likely change significantly in tomorrows update. The Northern Windward’s and Leewards should expect heavy rains and high winds from this disturbance.
There is much less to talk about in terms of the Eastern Atlantic disturbance 96L.
This is the early evening satellite image of 96L. I’ve marked the APPROXIMATE center in the black circle and the heaviest thunderstorms inside the red lines. This system is lacking any healthy upper level air pattern and that will be one of its top priorities if it wants to develop into a TD.
This graphic shows the satellite imagery on the top and the microwave imagery on the bottom. On the bottom, I’ve highlighted the heaviest thunderstorms in black and the center in red. as you can see, it’s a lopsided storm with all the convection to the western side. this is caused by strong upper level winds out of the east. The track and intensity model side is down as I write this do I will not be able to display those graphics at the moment but hopefully it will be back online tomorrow. The forecast from the other models look the same as yesterday, out to sea (OTS) as an open wave. This is the forecast I will stick by as well.
This map show the shear (highest=red, decreasing to black, the lowest) I highlighted 96L in the red circle and its expected track shown as the red arrow. Also highlighted is the problematic area of high shear outlined in black.
In the tropics elsewhere, we have a tropical storm in the eastern Pacific named Kiko. This storm has top winds of 60 mph. Other information from the NHC is listed below.
2:00 PM PDT Sat Aug 31
Location: 19.3°N 116.2°W
Moving: NNW at 5 mph
Min pressure: 1000 mb
Max sustained: 60 mph
This is the data from the NHC on TS Kiko.
This shows Koko’s position in the Eastern Pacific as well as the satellite imagery. As you can see, shear is also a problem for Kiko as most of its convection is located to the east of the center.
This map shows the satellite imagery on top and the microwave imagery on the bottom. Notice on this microwave imagery, there is a substantial amount of strong thunderstorms signaling a stronger system. Also notice it’s problem with shear- all the convection is pushed to the east signaling strong winds out of the west.
In other weather news…
Invest 96L kills 55 people in Mali from heavy rains. Link
A cold front moving across the eastern US promises a rainy Labor day for the East Coast. Showers/ thunderstorms are possible across the eastern 1/3 of the country Sunday but the real action kicks off Monday with widespread rain and embedded thunderstorms.
Tropical depression Kong-Rey drenched Taiwan causing widespread flooding. Link
I’ll publish another update tomorrow.