MY 2021 ATLANTIC HURRICANE SEASON BIRDSEYE VIEW POST #44 (Weekend Edition)
*******Note that forecasts and outlooks in this post are NOT the official forecast from the National Hurricane Center (NHC). They are my own detailed views on the Atlantic tropics based on current observations and latest computer model runs. As such do not make decisions based on my posts...consult news media...watches and warnings from your local weather office...and any evacuation orders issued by local governments to make the most informed and best decisions. Visit the NHC website hurricanes.gov (hurricanes dot gov) for the latest watches/warnings and official forecasts on active tropical cyclones.**********
...THURSDAY JULY 8 2021 4:20 PM EDT...
Satellite image as of 1830Z. Areas of interest circled in yellow are not mentioned in the NHC tropical weather outlook. Areas circled in a green dashed line are in the NHC 5-day tropical weather outlook. Areas circled in a solid green line are in the NHC 2-day tropical weather outlook:
NHC TAFB Surface Analysis 1200Z:
GFS Model Upper-Level Winds 1200Z:
Note that the weekend edition posts (without the computer model summary and above-style charts created by mobile phone) will continue this week as I am currently on vacation.
See Tropical Storm Elsa section below for additional details on the storm. See area of interest #1 section below for an update on the surface low pressure area centered over south Texas. Elsewhere…a pair of closely spaced tropical waves of low pressure in the eastern tropical Atlantic appear to be merging near 35W longitude. However this area of disturbed weather lacks organized thunderstorms due to dry Saharan air…and none of the recent runs of global models forecasted development here.
TROPICAL STORM ELSA...After Elsa dipped to 40 mph max sustained winds as it crossed northeast through the Carolinas…it has re-strengthened to 45 mph maximum sustained winds even though the thunderstorm intensity on colorized infrared satellite continues to fade. This indicates Elsa is becoming increasingly supported by the stronger eastern divergence zone of the incoming upper trough approaching from central North America…and will spend the next 24 hours transitioning into a vigorous frontal cyclone supported by the upper trough as it rakes across the coastal northeastern US. The forecast track remains unchanged with such a strong model consensus.
(1) Preparations for gusty winds and coastal sea swells should have been completed by now from the coastal Carolinas to coastal Delaware:
**Where land friction is higher…inland over the eastern North Carolina and eastern Virginia…wind will only be breezy at worst…especially as Elsa’s thunderstorms have weakened which will make it difficult to mix stronger wind aloft down to the surface. Therefore wind damage potential is extremely low.
**Heavy rain with flash flooding potential is expected from northeast North Carolina to Delaware.
**Surface southerly flow on the east side of Elsa and upper southwesterly flow over Elsa will create wind shear and thus tornado potential east of Elsa’s center. As of this writing…a tornado watch is in effect for southeast Virginia and northeastern North Carolina. Tornado potential further north will be less likely as land areas will tend to be under or west of Elsa’s surface center on the current forecast track.
(2) Here are some of the strongest National weather service station reports of wind (in mph) over the last few hours across the North Carolina to Delaware region. Where surface friction is higher…inland areas are seeing much less wind (check the list below from Fayetteville and down):
**Wilmington NC…sustained 23…gust 40 (1:53 PM EDT)
**Morehead City NC…sustained 23…gust 37 (now)
**Hatteras NC…sustained 20…gust 32 (now)
**Corolla NC…sustained 5 (now)
**Elizabeth City NC…sustained 15…gust 30 (10:54 AM EDT)
**Norfolk VA…sustained 12…gust 20 (8:59 AM EDT)
**Salisbury MD…sustained 17…gust 24 (12:54 PM EDT)
**Dover DE…sustained 14 (now)
**Fayetteville NC…sustained 22…gust 32 (now)
**Greenville NC…sustained 14…gust 26
**Rocky Mount NC…sustained 12…gust 23 (2:53 PM EDT)
**Raleigh NC…sustained 15…gust 25 (11:51 AM EDT)
**Richmond VA…sustained 12 (now)
**Annapolis MD…sustained 14…gust 26 (now)
(3) Interests across the northeastern US coastal region from New Jersey to Maine should be finishing preparations for:
**Gusty winds with some damage from coastal New Jersey to coastal Massachusetts…prepare for possible power outages if you live in a community with above-ground power lines
**Coastal sea swells from coastal New Jersey to coastal Maine.
**Heavy rainfall with flash flooding potential expected from New Jersey to Maine…including inland areas.
**Elsa will move quickly through the region by early tomorrow (Friday).
(4) Interests across Nova Scotia and Newfoundland can also expect gusty winds…coastal sea swells…and heavy rainfall from the remnant frontal cyclone of Elsa late Friday and early Saturday.
******Infohurricanes.com forecast. Visit hurricanes.gov (hurricanes dot gov) for official forecast***********
0 Hr Position (1200Z Jul 8)…45 mph maximum sustained wind tropical storm centered over central North Carolina at 35N-79.7W
IOH 24 Hr Forecast (1200Z Jul 9)…Frontal cyclone centered just south of Cape Cod Massachusetts at 41N-70.5W
AREA OF INTEREST #1…The surface low pressure area that formed near the northwest Gulf of Mexico and over south Texas…with the support of split flow upper divergence between the current southwest US upper ridge cell and southeast US upper vorticity…has been introduced into the NHC tropical weather outlook. More recently…a small lobe of this upper vorticity has shifted southwest over east Texas while steered around the southwest US upper ridge cell. This feature has also further aided the surface low pressure by generating a focused zone of upper divergence. At the same time however…the upper vorticity lobe is also pushing the strongest thunderstorm activity to the east and out over the northwest Gulf of Mexico…which explains why the surface low pressure center over south Texas (near 27N-98W) is a thin cloud swirl void of thunderstorms as of today.
The west side of the Atlantic surface ridge is trying to keep this system pushed north which will keep the center over land…therefore I agree with the NHC 0% odds of tropical cyclone formation. The center has been very slow to move if at all due to Elsa and the Great Lakes frontal low pressure keeping the west side of the Atlantic surface ridge weak. However some north drift is anticipated in the next 24 hours as Elsa and the frontal low depart the region…and the west side of the Atlantic surface ridge expands with the support of the western convergence zone of the upper trough passing through central and eastern North America. Meanwhile the upper vorticity lobe over east Texas is forecast to remain stationary in between west Atlantic and southwest US upper ridge cells…with this lobe keeping the heavy rainfall suppressed inland. However coastal regions of Texas and south Louisiana may see heavy rainfall with flash flooding potential where the divergence zone on the southeast edge of the upper vorticity lobe is present…which could allow for atmospheric lift and thunderstorms. The additional rainfall is not particularly welcome over coastal Texas where the ground has already been saturated by this system over the last day or so…flash flood advisories remain posted here as of this writing.
******Infohurricanes.com outlook. Visit hurricanes.gov (hurricanes dot gov) for official outlook***********
IOH 24 Hr Outlook (1200Z Jul 9)…0% chance of tropical cyclone formation (south Texas near 29N-98W)