Tag Archives: south Florida

Disturbance Organizes over Northwest Caribbean Sea

A tropical disturbance, designated as Invest 91L, organized over the Northwest Caribbean Sea on Wednesday. At 8:00 a.m. EDT on Wednesday the center of Invest 91L was located at latitude 18.7°N and longitude 87.4°W which put it about 75 miles (120 km) east of Chetumal, Mexico. Invest 91L was moving toward the northeast at 3 m.p.h. (5 km/h). The maximum sustained wind speed was 30 m.p.h. (50 km/h) and and there were wind gusts to 40 m.p.h. (65 km/h). The minimum surface pressure was 1006 mb.

A center of circulation appeared to be spinning over the Northwest Caribbean Sea just to the east of the Yucatan Peninsula on visible satellite loops on Wednesday morning. The circulation center was designated as Invest 91L. The center was inside a larger tropical disturbance over the Northwest Caribbean Sea and Yucatan Peninsula. The strongest thunderstorms were occurring in bands in the eastern half of Invest 91L. Bands in the western half of the system were over the Yucatan Peninsula and those bands consisted primarily of showers and lower clouds. Storms in the eastern half of Invest 91L generated upper level divergence that pumped mass away to the east of the tropical disturbance.

Invest 91L will move through an environment that will be favorable for the formation of a tropical depression during the next 36 hours. Invest 91L will move over water where the Sea Surface Temperatures are near 28˚C. An upper level trough over the western Gulf of Mexico and an upper level ridge over the Northwest Caribbean Sea will interact to produce southwesterly winds that will blow toward the top of Invest 91L. Those winds will cause some vertical wind shear. The vertical shear will somewhat inhibit the formation of a tropical depression. However, the upper level ridge will also enhance the upper level divergence over Invest 91L. More upper level divergence would cause the surface pressure to decrease. The National Hurricane Center is indicating the probability is 80% that a tropical depression forms from Invest 91L. A reconnaissance plane is tentatively scheduled to investigate the system on Thursday, if necessary.

The upper level trough over the western Gulf of Mexico and the upper level ridge over the Northwest Caribbean Sea will steer Invest 91L slowly toward the northeast during the next several days. On its anticipated track, Invest 91L will move toward western Cuba and South Florida. Invest 91L could bring gusty winds and locally heavy rain to western Cuba and South Florida later this week.

Tropical Depression Nine Forms Over Bay of Campeche

More thunderstorms formed near the center of a small low pressure system over the Bay of Campeche and the National Hurricane Center classified the low as Tropical Depression Nine (TD9) at 11:00 p.m. EDT on Tuesday.  The center of TD9 was located at latitude 19.4°N and longitude 92.9°W which put it about 160 miles west of Campeche, Mexico and about 850 miles west-southwest of Key West, Florida.  TD9 was moving toward the east at 6 m.p.h.  The maximum sustained wind speed was 35 m.p.h. and the minimum surface pressure was 1000 mb.  The government of Mexico has issued a Tropical Storm Warning for the portion of the coast from Celestun to Frontera.

Westerly winds in the upper levels are still creating wind shear over the top of TD9 and most of the thunderstorms are located in the eastern half of the circulation.  However, the upper level wind speed is expected to diminish and TD9 is likely to intensify into Tropical Storm Hanna on Wednesday.  The westerly winds are also likely to continue to push TD9 toward the east or east-northeast during the next 24 hours.

 

Potential Tropical Cyclone Developing Over Bay of Campeche

A reconnaissance plane found a small center of low pressure within a broader area of low pressure over the Bay of Campeche on Tuesday afternoon.  The plane also found winds to near tropical storm force.  At the 3:00 p.m. EDT the low was centered at latitude 19.3°N and longitude 93.7°W which put it about 350 miles northwest of Campeche, Mexico and about 850 miles west-southwest of Key West, Florida.  The low was moving toward the east at 6 m.p.h.  The maximum sustained wind speed was 38 m.p.h. and the minimum surface pressure of 1001 mb.

Thunderstorms are forming mainly on the southern and eastern sides of the center.  The low could be pulling in some of the drier air over the northern Gulf of Mexico, which may be limiting convection on the northwest side of the low.  Westerly winds in the upper levels are also generating wind shear, which is inhibiting the development of the low.  On the other hand, the low is over Sea Surface Temperatures (SSTs) that are warmer than 29°C and there is plenty of energy in the ocean to support the development of a tropical cyclone.  The pressure has fallen about 5-6 mb in the past 12 hours and so the low appears to be getting stronger.  If more thunderstorms form around the center of the low, it could be classified as a tropical depression or a tropical storm.

The westerly winds in the upper and middle levels are pushing the low slowly toward the east.  Guidance from the forecast models seems to be divided into two main possibilities.  One group of models keeps the low relatively weak and forecasts it to move eastward across the Yucatan peninsula and into the northwestern Caribbean Sea before turning it northeastward and moving the low across the Bahamas.  A second group of models predicts that the low will be a bit stronger and that the upper level flow will turn it northeastward sooner and move the low across southern Florida.  If that second scenario occurs, the low could bring stronger winds and heavy rainfall to parts of south Florida.