INVEST98L Will Soon be Upgraded to a T.D. as TD Danny Continues to Weaken

By: Steve Gregory , 2:21PM,GMT on August 24,2015

MONDAY, 24AUG15 / 9:15AM CDT
A ‘LIMITED’ FULL WX UPDATE WILL BE POSTED LATER TODAY

NAVY POSTS ‘CYCLONE ALERT’ FOR INVEST 98L

While NHC has not officially upgraded 98L to a Depression yet – it will shortly since the NAVY has issued a Cyclone Alert on their Track/Intensity Forecast Chart. This occurs because NHC coordinates with the NAVY – and advises them that they (NHC) intended to upgrade 98L to a Tropical Cyclone. While no specific time frame for the upgrade is provided – it USUALLY occurs within an hour of the Alert being issued. However, I have seen a few longer delays of over 6 hours.

The developing cyclone is located about 1,000NM east of the Leeward Islands, and is heading due west (270˚) at a fairly good clip of ~20Kts.

TROPICAL DEPRESSION DANNY

NHC officially downgraded DANNY to a Depression overnight, and dissipation to a remnant Low is expected within 36 hours as it moves slowly westward. The low level center is located about 20NM S/SW of Guadeloupe in the Leeward Islands, but the bulk of convection is now well east of the surface center – with occasional winds gusting to 30Kts in isolated convection. Whether or not the system will still produce major rainfall on Puerto Rico is not clear – and will be dependent on how well the convection holds up as it moves into the NE CARIB during the next couple days.

A ‘Limited’ WX Update on the Tropics and latest US Temperature Anomaly Charts will be posted later today.

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Fig 1: Visible image of INVEST98L Overnight IR imagery and initial VIS images this morning suggest convection has increased in vicinity of the Low Level Circulation Center (LLCC) – justifying an upgrade to a Tropical Depression. The system is moving quickly to the west at 22Kts – and this forward motion should continue for the next few days,


Fig 2: INVEST 98L Track and Intensity Forecast chart from the US NAVY Whenever you see this type of ‘Track/Intensity Forecast Chart from the NAVY – it indicates that NHC has coordinated with them – advising that NHC will be upgrading an INVEST to a Tropical Depression ‘shortly’.


Fig 3: Early 12Z Model run forecasts for INVEST 98L.The forecast tracks are very similar to yesterday, though the forward motion is now faster than originally called for. The cyclone should be near the Leeward Islands by FRI – and is now expected to track across the Bahamas over the weekend as a strong Tropical Storm, or low end CAT 1 Hurricane. Considering the very warm waters that lie ahead, and ‘modest’ shear intensities expected by that time – we would normally expected to see at least some of these models calling for a much stronger storm. However, the persistent issue of dry air this year is the primary cause for the muted intensification forecasts.

✭ The next Regular (but ‘Limited’) Weather Update will be Issued Later Today ✭
NOTE: Assuming DANNY dissipates and KILO does not become a NEAR TERM threat to Hawaii –
I’ll be returning to the ‘normal’ 3 Full WX Update Postings a week starting on Wednesday.

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Steve