Hurricane Hunters set to fly Invest 99L later today

The tropical disturbance we’ve been tracking since last weekend – that moved from the southwestern Caribbean and through parts of Central America this week – has reemerged over the Bay of Campeche and extreme southern Gulf of Mexico this morning, where it has a narrow window for development before moving inland over Mexico on Saturday.

Overnight satellite wind measurements indicated the sharpest turning of winds and greatest spin associated with the fledgling system – designated Invest 99L by NHC yesterday – was tucked away down in the southern Bay of Campeche.

(University of Wisconsin (UW) Cooperative Institute for Meteorological Satellite Studies (CIMSS))

Concentrated showers and thunderstorms with 99L waned during the overnight hours but are re-firing this morning near the small area of spin. If thunderstorm activity persists and NHC deems further investigation necessary, Air Force Reserve Hurricane Hunters are scheduled to fly a mission into 99L this afternoon.

While the disturbance remains over water, conditions appear largely conducive for development. Water temperatures are cracking 86 degrees in this part of the Bay of Campeche and only some light easterly wind shear will stand in the way of thunderstorm growth.

The biggest factor working against development will be 99L’s limited time over water. Though it may hug the coast for the next 24 hours, by tomorrow it will be moving inland over parts of northern Mexico.

A surge of tropical moisture, which could stretch into portions of Deep South Texas, will accompany the disturbance as it progresses inland over the weekend.

Looking outward across the greater tropical Atlantic, we continue to see conditions priming for the upcoming hurricane season peak.

As we discussed in yesterday’s newsletter, dust cover is coming down and waters are following the warm trend of recent active seasons.

While a full 85 percent of tropical activity typically arrives after August 19th (in other words, it’s still early), we’ve seen a surprisingly sleepy start so far despite calls for a very busy year.

In addition to sinking air plaguing the eastern Atlantic, much higher than average wind shear has been an issue through the Caribbean so far this August.


The higher-than-average Caribbean wind shear is very uncharacteristic of La Niña years, when shear is typically reduced through the Caribbean.

La Niña – cooler than average waters around the equator in the eastern Pacific – also usually tamps down tropical activity in the eastern Pacific, which has been anything but quiet this year. Outflow from eastern Pacific storminess has likely contributed to the high wind shear over the western Atlantic so far this August.

With activity quieting down across the eastern Pacific in the coming weeks and the Atlantic moving into a more conducive configuration, wind shear is forecast to relax into early September.


Although long-range models are still sorting through the finer details, we’ll keep an eye out to the deep tropical Atlantic in the weeks ahead as the environment becomes more hospitable to disturbances rolling through hurricane alley.