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Vinny Findley

What does PRE mean

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I'm following the Hurricane Isaias thread and cannot figure out or find what is meant by PRE. What is this referring to? Thank you in advance.

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On 8/1/2020 at 10:27 AM, Vinny Findley said:

I'm following the Hurricane Isaias thread and cannot figure out or find what is meant by PRE. What is this referring to? Thank you in advance.

Sorry for the delayed response, hope this helps:

 

Predecessor Rainfall Event. If the atmosphere is configured properly in advance of an approaching tropical cyclone, it opens the door for moisture directly from the system to be advected poleward, sometimes well in advance of the tropical cyclone arriving... If it actually arrives at all. Some of the more tell tale signs are a strong, meridionally aligned jet stream, usually with an embedded strong jet streak to the NW of the storm.

 

namconus_uv250_us_1.png

 

Due to the tropical cyclone approaching the right entrance region of the upper level jet, this allows for very favorable upper level lift & provides a fetch from the TC to areas well N of the system. These are also most often associated with the threat area in question being located on the eastern flank of deep layer troughs (trough of low pressure existing vertically through the troposphere from the low levels to the higher ones, i.e. surface, 850mb, 700mb, 500mb, 300mb, 200mb) - With most PREs, rainfall totals from the PRE itself will typically exceed 4" in a 24 hours period, though most PRE's usually last 12 hours or less. Typically, the PRE will occur several hundred miles away from the storm's center. Where they precisely decide to manifest can be difficult to nail down by numerical computer modeling. But the signature for a PRE to occur somewhere N of the system is usually well pronounced days in advance.

 

It should be noted that not all rainfall that occurs N of a tropical cyclone is always associated with a PRE. Sometimes its simple interaction with a frontal boundary or other form of forcing.

 

Though when they do occur, they can be especially problematic because they serve to drench an area in advance of the tropical cyclone itself. When the rain shield directly associated with the tropical cyclone subsequently moves in, it serves as a double-tap, which usually results in significant flooding issues, regardless of the area's antecedent soil/river conditions (see Hurricane Agnes or Floyd for example.)

 

https://journals.ametsoc.org/mwr/article/138/8/3272/71161/Predecessor-Rain-Events-ahead-of-Tropical-Cyclones

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7 hours ago, CCB! said:

Sorry for the delayed response, hope this helps:

 

Predecessor Rainfall Event. If the atmosphere is configured properly in advance of an approaching tropical cyclone, it opens the door for moisture directly from the system to be advected poleward, sometimes well in advance of the tropical cyclone arriving... If it actually arrives at all. Some of the more tell tale signs are a strong, meridionally aligned jet stream, usually with an embedded strong jet streak to the NW of the storm.

 

namconus_uv250_us_1.png

 

Due to the tropical cyclone approaching the right entrance region of the upper level jet, this allows for very favorable upper level lift & provides a fetch from the TC to areas well N of the system. These are also most often associated with the threat area in question being located on the eastern flank of deep layer troughs (trough of low pressure existing vertically through the troposphere from the low levels to the higher ones, i.e. surface, 850mb, 700mb, 500mb, 300mb, 200mb) - With most PREs, rainfall totals from the PRE itself will typically exceed 4" in a 24 hours period, though most PRE's usually last 12 hours or less. Typically, the PRE will occur several hundred miles away from the storm's center. Where they precisely decide to manifest can be difficult to nail down by numerical computer modeling. But the signature for a PRE to occur somewhere N of the system is usually well pronounced days in advance.

 

It should be noted that not all rainfall that occurs N of a tropical cyclone is always associated with a PRE. Sometimes its simple interaction with a frontal boundary or other form of forcing.

 

Though when they do occur, they can be especially problematic because they serve to drench an area in advance of the tropical cyclone itself. When the rain shield directly associated with the tropical cyclone subsequently moves in, it serves as a double-tap, which usually results in significant flooding issues, regardless of the area's antecedent soil/river conditions (see Hurricane Agnes or Floyd for example.)

 

https://journals.ametsoc.org/mwr/article/138/8/3272/71161/Predecessor-Rain-Events-ahead-of-Tropical-Cyclones

Yes it helped a lot. I finally found out what it was because it was spelled out, but your response was much more in detail. Much appreciated. We had a squall line come through up here in RI as the storm was passing NYC. 20 minutes a few gusts to 60 or maybe a little over that and 156,000 without power in RI and another 200,000+ thousand in southeast ma. I just couldn't imagine even a cat 1 riding up the center of RI If a 20 minute squall line with 60 MPH winds did this much damage. Strong cat 2 and we're in a world of shit up here. Thanks again for the detailed response.

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