Increased Chances for TD 6, Jimena A Cat 4, and Kevin patient

Hurricane Jimena became a category four hurricane this morning while Kevin is taking it’s time relaxing in the warm Pacific oceans – a threat only to shipping lanes.  Last night I did a very detailed explanation on why Jimena intensified so quickly.  This morning, I’ll explain why the same is not happening to Kevin.  Or rather, why it’s not intensifying much at all.  Also, the National Hurricane Center has increased the odds of development for Invest 94L and sent a warning to the Lesser Antilles.  I’ll start with 94L.

Jump to:

• Invest 94L
• Hurricane Jimena
• Tropical Storm Kevin

Invest 94L

The National Hurricane Center estimates the wave has a central pressure of 1009mb and is located near 11°N, 44°W, moving west between 15-20kts.  A QuickSCAT pass at 3:53AM EDT showed a very sharp wave axis oriented south-southwest to north-northeast.  There are numerous wind barbs of 20kts.  There are also many 30kt wind barbs in the northern quadrant with a 40kt wind barb a bit further north from the center.  I’m damn-near positive the NHC would have upgraded this to a Tropical Storm Erika based on that 40kt wind barb had the wave center closed to a surface low.  But, until that occurs, the NHC is not upgrading this system.  However, they have notated in their last tropical outlook that residents in the Lesser Antilles should watch the system closely.  Don’t expect any watches or warnings issued until this thing gets a surface low.

IR satellite imagery shows some cool cloud tops to the west of the axis,  -70°C to be exact.  But, this is a small are dozens of miles west of the wave axis.  Most of the coldest cloud tops are in the -50°C range.  Even that, however, is off to the west of the axis.  There is no deep convection over the center of the wave axis as of this writing. While there is a slight possibility the wave could close off a surface low without the convective development over the axis, it will not be easy.  Convection will draw in moisture to the center and make the transition from a tropical wave to a tropical cyclone much easier.

This will be complicated a bit by the fact there is considerable dry air near the wave.  Precipitable water values are 50+mm/in² on an axis running from 8°N, 52°W northeast to 16°N, 40°W and southeast away from the wave.  To the northwest of the wave water values are in the 30′s as well as the southeast.  Essentially, the wave will likely draw in some drier air from it’s northwest and southeast as well as the more moist air from the southwest and northeast.  This will lead to some bursts of convection, perhaps deep convection, in the wave but will also lead to these bursts being short-lived.  Essentially, it’ll hamper the storms potential development into a serious cyclone – by serious, I mean even a strong tropical storm.  I’m not saying it won’t happen.  I’m saying it won’t be easy.

Furthermore, SST’s are favorable for supporting cyclone development.  However, oceanic heat content is low so even if there were an abundance of moisture available, it is unlikely the wave would go through a rapid intensification cycle similar to Jimena.

Current, Invest 94L is in an area of favorable development with light upper-level wind shear and an anticyclone above.  This will help draw used energy from the system.  However, the system is likely to move into a slightly unfavorable upper-level environment in about three days which would hamper any intensification (provided it has developed before that time).  This is if the system goes north of the Lesser Antilles as is forecast by several computer models.  However, several computer models also take the system into the northern Lesser Antilles and into the northeast Caribbean.  This will ultimately depend on how fast this system becomes cyclonic.

Hurricane Jimena

I did a pretty lengthy discussion on what was going on with Hurricane Jimena yesterday (see Rare Hurricane Jimena exploding) so I’ll just focus on the changes since then which are minimal.

Hurricane Jimena became a category four storm this morning with winds of 115mph.  As you can see on the visible image this morning, that is one impressive hurricane with about a 10 to 15-mile-wide eye.  The central dense overcast (CDO) has numerous undulating waves at the top which is classic of major hurricanes.  Furthermore, if you look all around the storm you can see cirrus clouds fanning from every quadrant – a sign of great outflow.  Jimena is consuming the energy of the warm humid air and extremely warm sst’s and using that energy to grow.  Then it is removing the “waste” to allow for the consumption of more energy.  Jimena is in a perfect environment for strong tropical cyclones.

In the image below (three hours old at the time of this posting) you can see a well-defined eyewall in Jimena.  This was lacking yesterday and is a big reason why the strengthening trend had halted.  However, Jimena is in sync with itself now and, provided there are no eyewall replacement cycles which is likely, the storm can grow even stronger.  The latest advisory by the NHC puts Jimena peaking at 125kts or 145mph winds – category four.  That intensity forecasting  is extremely difficult to do it should not be a surprise if Jimena grows into a category five hurricane.  In fact, it should be expected.

In addition, Jimena’s cdo is between -70°C and -80°C with a small patch in the north above -80°C.  Jimena is not as symmetric as I would like to see in a hurricane of this magnitude.  However, that shouldn’t prevent additional strengthening.

There is a slight amount of drier air to the northwest of the hurricane.  However, this could limit growth to some extent but is more likely not enough to retard convective development.

Computer forecast models vary greatly in the future of Jimena from well offshore Baja to coming inland at Baja to entering the Gulf of California.  The latest NHC forecast splits the uprights with a hurricane running parallel to the Baja coastline.

Track Hurricane Jimena and get the latest NHC forecast and wind radii on our interactive hurricane tracking chart.

Tropical Storm Kevin

Tropical Storm Kevin is not following in the footsteps of Jimena as far as rapid intensification goes.  Why not?

For one, easterly shear is helping suffocate the system a bit.  This shear is forcing used energy back into the center of the storm which is prohibiting the storm from processing new energy.

Second, there’s more dry air in the region.  Kevin’s surrounding atmosphere has a moisture content similar to that of Invest 94L  with dry(er) air to the northwest and southeast.  So, there’s less energy available for Kevin to consume.  Though precipitable water values are 50+mm/in² closest to Kevin and from the southwest-northeast,  those values are in the 30′s to the northwest and southeast.

In addition, oceanic heat content is low.  Kevin is over 28°C ocean waters – not bad at all for any cyclone.  But, the heat content is very low.  Too many storms and hurricanes have passed through this region this year consuming available energy.  Kevin might as well be developing in late May, early June for this type of oceanic conditions.  The boundary layer, or the region of air just above the water surface, just isn’t capable of supporting any rapid intensification.  Kevin doesn’t have much time either for considerable strengthening – as you can see in the OHC map below, Kevin will be moving over waters that, while sustainable for tropical cyclones, is not sustainable for much intensification.  That along with the light but consistent wind shear is why the NHC is not expecting Kevin to grow into a hurricane (well, that and possible interaction with an upper low and Jimena).

Kevin looks decent on satellite imagery with the mass of convection over and to the west of the center.  However, the cdo isn’t particularly cold with values in the -50′s,  In addition, there aren’t really any banding features that you’d like to see in young tropical storms.

Finally,there are a number of questions of what atmospheric forces will control Kevin’s destiny from an upper-level low to Jimena.  You can see that in the spaghetti model plots below.  Some models want to shift control of Kevin from Jimena to an expected developing low.  Some want a building high pressure ridge to take control of Kevin.  The NHC has gone with a northwest motion over the next five days.  It’s forecasts like this that will really drop average errors.  The NHC could be right on with this forecast.  And they may be horribly wrong.  Thankfully, Kevin’s in a region where it doesn’t really matter.